SUM Summit Materials Inc

On November 24, 2024, Summit Materials, Inc. (referred to as “Summit”), Quikrete Holdings, Inc. (referred to as “Quikrete”) and Soar Subsidiary, Inc., a wholly owned subsidiary of Quikrete (referred to as “Merger Sub”), entered into an Agreement and Plan of Merger that provides for the acquisition of Summit by Quikrete (such agreement, as it may be amended from time to time, referred to as the “merger agreement”). Pursuant to the terms of the merger agreement, Merger Sub will merge with and into Summit (referred to as the “merger”), with Summit surviving the merger as a wholly owned subsidiary of Quikrete (referred to as the “surviving corporation”). The respective boards of directors of Summit and Quikrete have unanimously approved the merger agreement and the merger.

Upon the terms and subject to the conditions of the merger agreement, at the effective time of the merger, you will be entitled to receive, for each share of Class A common stock, par value $0.01 per share, of Summit (“Summit Class A common stock”) or Class B common stock, par value $0.01 per share, of Summit (“Summit Class B common stock” and, together with the Summit Class A common stock, the “Summit common stock”) that you own immediately prior to the effective time of the merger, $52.50 in cash without interest and subject to deduction for any required withholding (referred to as the “merger consideration”). The merger consideration represents an approximately 29.2% premium over the unaffected price of Summit common stock of $40.62 (which was the closing trading price on October 23, 2024, the last trading day prior to the public disclosure of the receipt by Summit of a non-binding acquisition proposal).

The Summit board of directors has unanimously (i) determined that it is in the best interests of Summit and its stockholders, and declared it advisable, that Summit enter into the merger agreement and consummate the transactions contemplated thereby, (ii) approved and declared advisable the execution and delivery of the merger agreement and the consummation of the transactions contemplated thereby, including the merger, and (iii) directed that the merger agreement and the transactions contemplated thereby be submitted for consideration by Summit stockholders entitled to vote thereon at a meeting thereof.

At the special meeting of Summit stockholders described in the accompanying proxy statement (referred to as the “special meeting”), you will be asked to approve the merger agreement proposal and to vote on other merger-related matters. The Summit board of directors unanimously recommends that Summit stockholders vote “FOR” the merger agreement proposal and “FOR” each of the other proposals described in the accompanying proxy statement.

Contemporaneously and in connection with the execution of the merger agreement, in their respective capacities as record and beneficial owners of Summit common stock, Cementos Argos S.A., a sociedad anónima incorporated in the Republic of Colombia (“Cementos”), Argos SEM LLC, a Delaware limited liability company (“Argos SEM”) and Valle Cement Investments, Inc., a sociedad anónima incorporated in the Republic of Panama (“Valle Cement” and, together with Cementos and Argos SEM, the “supporting stockholders”) entered into a voting agreement (referred to as the “voting agreement”) with Quikrete, pursuant to which the supporting stockholders agreed, among other things, to vote their shares of Summit common stock in favor of any proposal to approve the adoption of the merger agreement. In connection with the execution of the voting agreement, Summit waived, to the extent implicated by the execution of the voting agreement or the performance by the supporting stockholders of their obligations thereunder, all restrictions in the stockholder agreement, dated January 12, 2024, among Summit, Cementos, Argos SEM, Valle Cement and, for the limited purposes set forth therein, Grupo Argos S.A. (the “stockholder agreement”) that would restrict the ability of the supporting stockholders to execute the voting agreement and perform their respective obligations thereunder, including a restriction on the supporting stockholders’ ability to vote all of their shares of Summit common stock in favor of the merger agreement proposal. For more information, please see the section of the accompanying proxy statement entitled “The Voting Agreement.” For more

information regarding the security ownership of the supporting stockholders, please see the section of the accompanying proxy statement entitled “Security Ownership of Certain Beneficial Owners and Management.”

Your vote is very important regardless of the number of shares of Summit common stock that you own. Quikrete and Summit cannot complete the merger without the approval of the merger agreement proposal by Summit stockholders holding at least a majority of the voting power of the shares of Summit common stock outstanding at the close of business on [record date], the record date for the special meeting. The failure of any Summit stockholder to vote will have the same effect as a vote against the approval of the merger agreement proposal. Whether or not you plan to participate in the special meeting, Summit urges you to submit a proxy in advance of the special meeting to have your shares voted by using one of the methods described in the accompanying proxy statement. If your shares are held in the name of a bank, brokerage firm or other nominee, please follow the instructions on the voting instruction card furnished by such bank, brokerage firm or other nominee. You must provide voting instructions by filling out the voting instruction card in order for your shares to be voted.

More information about Quikrete, Summit, the special meeting, the merger and the other proposals for consideration at the special meeting is contained in the accompanying proxy statement. Please carefully read the entire proxy statement and the annexes and documents included in, or incorporated by reference into, the proxy statement.

If you have any questions or need assistance voting your shares of Summit common stock, please contact Georgeson LLC, our proxy solicitor (referred to as “Georgeson”), by calling toll-free at (888) 755-6840.

On behalf of the Summit board of directors, thank you for your continued support.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED THE MERGER, PASSED UPON THE MERITS OF THE MERGER AGREEMENT, THE MERGER OR THE OTHER TRANSACTIONS CONTEMPLATED BY THE MERGER AGREEMENT OR DETERMINED IF THE ACCOMPANYING PROXY STATEMENT IS ACCURATE OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

The accompanying proxy statement is dated [•], 2025 and is first being mailed to Summit stockholders on or about [mailing date], 2025.

This is a notice that the special meeting of stockholders of Summit Materials, Inc. (referred to as “Summit”) will be held on [•], 2025, beginning at [•], Mountain Time (such meeting is referred to as the “special meeting”). The special meeting will be held in person at Summit’s principal executive offices at 1801 California Street, Suite 3500, Denver, Colorado 80202 and will be held for the following purposes:

The proxy statement of which this notice is a part (a) incorporates important business and financial information about Summit, Quikrete and Merger Sub from other documents that Summit has filed with the U.S. Securities and Exchange Commission (referred to as the “SEC”) and that are contained in or incorporated by reference into this proxy statement and (b) provides a detailed description of the merger and the merger agreement and the other matters to be considered at the special meeting, including the proposals listed above. Please refer to the accompanying proxy statement, including the merger agreement and the other annexes and documents included in, or incorporated by reference into, the accompanying proxy statement for further information with respect to the business to be transacted at the special meeting. You are encouraged to read the entire proxy statement carefully before voting. The Summit board of directors has unanimously (i) determined that it is in the best interests of Summit and its stockholders, and declared it advisable, that Summit enter into the merger agreement and consummate the transactions contemplated thereby, (ii) approved and declared advisable the execution and delivery of the merger agreement and the consummation of the transactions contemplated thereby, including the merger, and (iii) directed that the merger agreement and the transactions contemplated thereby be submitted for consideration by Summit stockholders entitled to vote thereon at a meeting thereof.

The Summit board of directors unanimously recommends that Summit stockholders vote “FOR” the merger agreement proposal, “FOR” the merger-related compensation proposal and “FOR” the adjournment proposal.

The Summit board of directors has fixed the close of business on [record date] as the record date for determination of Summit stockholders entitled to receive notice of, and to vote at, the special meeting or any adjournments or postponements thereof (referred to as the “record date”). Only holders of record of Summit common stock as of the close of business on the record date are entitled to receive notice of, and to vote at, the special meeting.

Under Delaware law, holders of Summit common stock who do not vote in favor of the merger agreement proposal will have the right to seek appraisal and obtain payment in cash for the fair value of their shares of Summit common stock, as determined by the Court of Chancery of the State of Delaware if the merger is completed, but only if they strictly comply with the procedures prescribed by Delaware law. These procedures are summarized in “Appraisal Rights of Summit Stockholders” beginning on page 92 of the accompanying proxy statement. In addition, the text of the applicable provisions of Delaware law is attached as Annex E to the accompanying proxy statement.

YOUR VOTE IS VERY IMPORTANT, REGARDLESS OF THE NUMBER OF SHARES THAT YOU OWN.

The merger cannot be completed unless the merger agreement proposal is approved by the affirmative vote, at the special meeting or by proxy, of holders of at least a majority of the voting power of shares of Summit common stock outstanding and entitled to vote thereon. Abstentions will be included in determining the presence of a quorum at the special meeting. Broker non-votes will not be included in determining the presence of a quorum at the special meeting.

If you fail to (1) return your proxy card, (2) grant your proxy electronically over the internet or by telephone or (3) attend the special meeting, your shares will not be counted for purposes of determining whether a quorum is present at the special meeting. Assuming a quorum is present, your shares will have the same effect as a vote “AGAINST” the proposal to adopt the merger agreement but will have no effect on the other proposals.

Whether or not you expect to participate in the special meeting, Summit urges you to submit a proxy to have your shares voted as promptly as possible either: (1) via the internet at www.proxyvote.com (see proxy card for instructions); (2) by telephone (see proxy card for instructions); or (3) by completing, signing and returning the enclosed proxy card in the postage-paid envelope provided, so that your shares may be represented and voted at the special meeting. If your shares are held in “street name” by a bank, brokerage firm or other nominee, please follow the instructions on the voting instruction card furnished by such bank, brokerage firm or other nominee. Any stockholder of record participating in the special meeting may vote even if such stockholder has returned a proxy card. However, if your shares are held in “street name” you must obtain a “legal proxy” from the bank, brokerage firm or other nominee to vote at the special meeting.

Summit stockholders of record as of [record date] will be able to participate in the special meeting.

If you have any questions about the special meeting, the merger, the proposals or the accompanying proxy statement, would like additional copies of this proxy statement, need to obtain proxy cards or other information related to this proxy solicitation or need help submitting a proxy or voting your shares of Summit common stock, you should contact:

Summit is a market-leading producer of aggregates and cement with vertically integrated operations that supply ready-mix concrete and asphalt in select markets. Summit is a geographically diverse, materials-led business of scale that offers customers in the United States and British Columbia, Canada high quality products and services for the public infrastructure, residential and non-residential end markets. Summit has a strong track record of successful acquisitions since its founding and continues to pursue high-return growth opportunities in new and existing markets. Summit Materials, Inc. was formed under the laws of the State of Delaware on September 23, 2014. The principal executive office of Summit is located at 1801 California Street, Suite 3500, Denver, Colorado 80202, and its telephone number is (303) 893-0012.

Quikrete is a privately owned family business founded in 1940. It is a leading building materials company based in Atlanta, Georgia. From the original yellow bag of premixed concrete, today Quikrete’s portfolio of brands includes Quikrete, Spec Mix, Rinker Materials, U.S. Pipe, Contech Engineered Solutions, Keystone Hardscapes, Pavestone, Custom Building Products, QPR, and other leading brands. The products produced by the collection of brands include packaged cementitious products, pavers, retaining wall systems, masonry units, tile grouts and thin sets, concrete pipe, box culverts, corrugated metal pipe, ductile iron pipe, engineered storm water systems, structural precast, and steel pedestrian and vehicular bridges. The company services the United States and Canadian commercial construction, residential, and infrastructure markets. This broad array of products and expertise allows Quikrete to provide nearly every product required for most any type of construction project. The principal executive offices of Quikrete are located at 5 Concourse Parkway, Suite 1900, Atlanta, GA 30328, and its telephone number is (404) 634-9100.

Merger Sub is a wholly owned subsidiary of Quikrete. Merger Sub was incorporated by Quikrete solely in contemplation of the transactions contemplated by the merger agreement, has not conducted any business and has no assets, liabilities or obligations of any nature other than as set forth in the merger agreement. The principal executive offices of Merger Sub are located at c/o Quikrete Holdings, Inc., 5 Concourse Parkway, Suite 1900, Atlanta, GA 30328, and its telephone number is (404) 634-9100.

A copy of the merger agreement is attached as Annex A to this proxy statement. Summit encourages you to read the entire merger agreement carefully because it is the principal document governing the merger. For more information on the merger agreement, see the section titled “The Merger Agreement” beginning on page 69 of this proxy statement.

Upon the terms and subject to the conditions of the merger agreement and in accordance with Delaware law, Merger Sub will merge with and into Summit, whereupon the separate existence of Merger Sub will cease and Summit will survive the merger as a wholly owned subsidiary of Quikrete.

The following diagrams illustrate in simplified terms the merger and the effect of the merger on the organizational structures of Quikrete and Summit.

The following diagram illustrates in simplified terms the organizational structure of Quikrete and Summit prior to the merger:

The following diagram illustrates in simplified terms the merger:

The following diagram illustrates in simplified terms the organizational structure of Quikrete and Summit after the merger:

At the effective time, each share of Summit common stock issued and outstanding immediately prior to the effective time (other than (x) shares held by Summit as treasury stock or held, directly or indirectly, by Quikrete, Summit, Merger Sub or any of their respective subsidiaries (referred to as “excluded shares”) and (y) shares of Summit common stock with respect to which appraisal rights are properly demanded and not withdrawn or lost (referred to as “dissenting shares”) under the General Corporation Law of the State of Delaware (referred to as the “DGCL”)) will be converted into the right to receive the merger consideration of $52.50 in cash, without interest and subject to deduction for any required withholding (referred to as the “merger consideration”). Each share of Summit preferred stock outstanding immediately prior to the effective time will automatically be canceled and retired for no consideration and will cease to exist.

For additional information on the consideration Summit stockholders will receive in connection with the merger, see the section titled “The Merger Agreement—Effect of the Merger on Summit Common Stock.”

Effective as of immediately prior to the effective time, each restricted stock unit that is subject to vesting conditions based solely on continued employment or service (each, a “Summit RSU”) and that is outstanding immediately prior to the effective time will fully vest and be canceled and converted into the right to receive an amount in cash equal to the product of (i) the merger consideration, multiplied by (ii) the number of shares of Summit common stock subject to such vested award of Summit RSUs. Notwithstanding the foregoing, any Summit RSUs that are granted in 2025 or later and that are outstanding immediately prior to the effective time will vest on a pro rata basis (rather than in full) as of immediately prior to the effective time, unless the award holder’s employment is being terminated without cause or due to a constructive termination upon the effective time, in which case such award holder’s Summit RSUs that are granted in 2025 or later will vest in full.

Effective as of immediately prior to the effective time, each restricted stock unit that is subject to vesting conditions based in whole or in part on performance goals (each, a “Summit PSU”) and that is outstanding immediately prior to the effective time will vest, based on performance at target, and be canceled and converted into the right to receive an amount in cash equal to (i) the merger consideration, multiplied by (ii) the number of shares of Summit common stock subject to such vested award of Summit PSUs.

Effective as of immediately prior to the effective time, each option to purchase Summit common stock (each, a “Summit option”) that is outstanding immediately prior to the effective time will fully vest, to the extent not vested previously, and be canceled and converted into the right to receive an amount in cash equal to (i) the excess, if any, of the merger consideration over the applicable exercise price per share of Summit common stock subject to such

vested award of Summit options, multiplied by (ii) the number of shares of Summit common stock subject to such award of Summit options; provided that if the applicable exercise price per share of Summit common stock of an award of Summit options is equal to or greater than the merger consideration, such award of Summit options will be canceled at the effective time for no consideration.

For additional information on the treatment of Summit equity awards in connection with the merger, see the section titled “The Merger (Proposal 1)—Interests of Summit’s Directors and Executive Officers in the Merger—Treatment of Summit Equity Awards.”

At its November 24, 2024 meeting held to evaluate the merger, the Summit board of directors unanimously (i) determined that it is in the best interests of Summit and its stockholders, and declared it advisable, that Summit enter into the merger agreement and consummate the transactions contemplated thereby, (ii) approved and declared advisable the execution and delivery of the merger agreement and the consummation of the transactions contemplated thereby, including the merger, and (iii) directed that the merger agreement and the transactions contemplated thereby be submitted for consideration by Summit stockholders entitled to vote thereon at a meeting thereof.

The Summit board of directors unanimously recommends that Summit stockholders vote “FOR” the merger agreement proposal, “FOR” the merger-related compensation proposal and “FOR” the adjournment proposal.

In evaluating the merger and the merger agreement and arriving at its determination, the Summit board of directors consulted with Summit’s senior management, Summit’s financial advisors, Morgan Stanley & Co. LLC (referred to as “Morgan Stanley”) and Evercore Group L.L.C. (referred to as “Evercore”), and Summit’s outside legal counsel, Davis Polk & Wardwell LLP (referred to as “Davis Polk”), and considered a number of substantive factors, both positive and negative, and potential benefits and detriments of the merger to Summit and Summit stockholders, as described in more detail in the section titled “The Merger (Proposal 1)—Summit’s Reasons for the Merger; Recommendation of the Summit Board of Directors.”

Summit engaged Morgan Stanley as its financial advisor in connection with the proposed merger. On November 24, 2024, Morgan Stanley rendered its oral opinion to the Summit board of directors (which was subsequently confirmed in writing by delivery of Morgan Stanley’s written opinion addressed to the Summit board of directors dated the same date) as to, as of November 24, 2024, and subject to the various assumptions made, procedures followed, matters considered, and qualifications and limitations on the review undertaken by Morgan Stanley as set forth in its written opinion, the fairness, from a financial point of view, to the holders of Summit common stock of the merger consideration to be received by such holders in the merger pursuant to the merger agreement.

The full text of Morgan Stanley’s written opinion, which describes, among other things, the assumptions made, procedures followed, matters considered and qualifications and limitations on the review undertaken, is attached as Annex C to this proxy statement. The description of Morgan Stanley’s opinion contained in this proxy statement is qualified in its entirety by reference to the full text of the opinion. Morgan Stanley’s opinion was directed to the Summit board of directors, in its capacity as such, and addressed only the fairness, from a financial point of view and as of the date of such opinion, to the holders of Summit common stock of the merger consideration to be received by such holders in the merger pursuant to the merger agreement. Morgan Stanley’s opinion did not address the relative merits of the transactions contemplated by the merger agreement as compared to other business or financial strategies that might be available to Summit, nor did it address the underlying business decision of Summit to enter into the merger agreement. Morgan Stanley’s opinion is not intended to be and does not constitute a recommendation as to how the Summit board of directors or any securityholder should vote or act on any matters relating to the proposed merger or otherwise.

For additional information, see the section titled “The Merger (Proposal 1)—Opinion of Summit’s Financial Advisor – Morgan Stanley.”

Summit retained Evercore to act as its financial advisor in connection with the merger. As part of this engagement, Summit requested that Evercore evaluate the fairness, from a financial point of view, of the merger

consideration to be received by the holders of Summit common stock (other than Quikrete or any subsidiary of Quikrete, Summit or any subsidiary of Summit, or holders of dissenting shares). At a meeting of the Summit board of directors held on November 24, 2024, Evercore rendered to the Summit board of directors its opinion to the effect that, as of that date and based upon and subject to the analyses, procedures, assumptions, limitations, qualifications and conditions described in Evercore’s opinion, the merger consideration of $52.50 in cash per share to be received by the holders of Summit common stock in the merger was fair, from a financial point of view, to such holders (other than Quikrete or any subsidiary of Quikrete, Summit or any subsidiary of Summit, or holders of dissenting shares).

The full text of the written opinion of Evercore, dated November 24, 2024, which sets forth, among other things, the procedures followed, assumptions made, matters considered and qualifications and limitations on the scope of review undertaken in rendering its opinion, is attached as Annex D to this proxy statement and is incorporated herein by reference. Summit encourages you to read this opinion carefully and in its entirety. Evercore’s opinion was addressed to, and provided for the information and benefit of, the Summit board of directors (in its capacity as such) in connection with its evaluation of the proposed merger. Evercore’s opinion did not, and the summary of its opinion and the related analyses set forth in this proxy statement do not, constitute a recommendation to the Summit board of directors or to any other persons in respect of the merger, including as to how any holder of shares of Summit common stock should vote or act in respect of the merger. Evercore’s opinion does not address the relative merits of the merger as compared to other business or financial strategies that might be available to Summit, nor does it address the underlying business decision of Summit to engage in the merger.

For additional information, see the section titled “The Merger (Proposal 1)—Opinion of Summit’s Financial Advisor – Evercore.”

Quikrete intends to fund the cash portion of the merger consideration with proceeds from new debt financing together with cash on hand. Concurrently with the entry into the merger agreement, Quikrete entered into a debt commitment letter (referred to as the “debt commitment letter”), pursuant to which certain financial institutions (referred to as the “lenders”) have committed to provide to Quikrete term debt financing in an aggregate principal amount of $9,200,000,000 (including up to $6,700,000,000 in bridge financing) together with a committed asset based revolving credit facility in an aggregate principal amount of up to $1,500,000,000 (subject to customary borrowing base limitations). The obligations of the lenders to provide debt financing under the debt commitment letter are subject to certain customary conditions, including (a) the execution and delivery of definitive documentation with respect to such financing in accordance with the debt commitment letter and (b) the consummation of the merger in all material respects in accordance with the terms and conditions of the merger agreement. The receipt of financing by Quikrete is not a condition to Quikrete’s obligations to complete the merger. For more information about the financing of the merger, see the sections titled “The Merger (Proposal 1)—Financing of the Merger” and “The Merger Agreement—Financing of the Merger.”

The receipt of cash in exchange for Summit common stock pursuant to the merger generally will be a taxable transaction for U.S. federal income tax purposes. U.S. Holders (as defined below under “Material U.S. Federal Income Tax Consequences of the Merger—U.S. Holders”) generally will recognize gain or loss for U.S. federal income tax purposes in an amount equal to the difference, if any between (a) the amount of cash received and (b) the U.S. Holder’s adjusted tax basis in the Summit common stock surrendered in exchange.

Except in certain specific circumstances described below under “Material U.S. Federal Income Tax Consequences of the Merger—Non-U.S. Holders,” a Non-U.S. Holder (as defined below under “Material U.S. Federal Income Tax Consequences of the Merger—Non-U.S. Holders”) generally will not be subject to U.S. federal income tax unless such Non-U.S. Holder has certain connections with the United States.

The U.S. federal income tax consequences described above may not apply to all holders of Summit common stock. You should read the section titled “Material U.S. Federal Income Tax Consequences of the Merger” for a more complete discussion of the U.S. federal income tax consequences of the merger to you. Tax matters are complicated and the tax consequences of the merger to you will depend on your particular tax situation. You should consult your tax advisor to determine the applicable U.S. federal, state, local and non-U.S. tax consequences of the merger to you.

The merger is subject to the requirements of the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended (referred to as the “HSR Act”), which prevents Summit and Quikrete from completing the merger until each of Summit and Quikrete files a Notification and Report Form with the Antitrust Division of the Department of Justice (the “DOJ”) and the Federal Trade Commission (the “FTC”) and the HSR Act waiting period is terminated or expires and no judgement, injunction, order or decree of a governmental authority shall have been entered and continue to be in effect. A transaction notifiable under the HSR Act may not be completed until the expiration of a 30-calendar-day waiting period following the parties’ filings of their respective HSR Act notification forms or the early termination of that waiting period. Quikrete may also choose to voluntarily re-start the initial 30-calendar-day waiting period by pulling and re-filing its Notification and Report Form prior to the expiration of the initial waiting period to give the agencies additional time to review the transaction. Before the expiration of the initial waiting period (or the re-started initial waiting period), the Antitrust Division of the DOJ or the FTC may issue a Request for Additional Information and Documentary Material (referred to as a “Second Request”). If a Second Request is issued, the parties may not complete the merger until they have observed an additional 30-day waiting period, which would begin to run only after both parties have substantially complied with the Second Request, unless the waiting period is terminated earlier, or the parties commit not to close for some additional period of time. Summit and Quikrete submitted the requisite Notification and Report forms under the HSR Act on December 6, 2024, and the initial waiting period will expire on January 6, 2025 at 11:59 p.m. Eastern Time, unless it is extended by Quikrete pulling and refiling the initial Notification and Report Form, a Second Request for additional information is issued, it is terminated earlier, or if Summit and Quikrete commit not to close for some additional period of time.

In addition, the closing of the merger is subject to the requirements of the Competition Act (Canada), which prevent transactions such as the merger from being completed until (i) certain information and materials are furnished to the Canadian Commissioner of Competition appointed under the Competition Act (Canada), and (ii) the applicable waiting period is terminated or expires (provided that the Canadian Competition Tribunal has not issued an order temporarily or permanently prohibiting closing), unless the requirement to submit the required information and materials is waived by the Canadian Commissioner of Competition. The parties submitted the required information to the Canadian Commissioner of Competition on December 9, 2024.

The merger is also subject to the prior approval of the United States Nuclear Regulatory Commission, the Alabama Department of Public Health, the South Carolina Department of Health and Environmental Control and the Iowa Department of Health and Human Services with respect to certain radioactive materials licenses held indirectly by Summit.

For more information about regulatory clearance relating to the merger, see the sections titled “The Merger (Proposal 1)—Regulatory Clearances and Approvals Required for the Merger” and “The Merger Agreement—Conditions to the Merger.”

Although the parties expect that the required regulatory clearance will be obtained, the parties cannot assure you that regulatory clearance will be timely obtained or obtained at all or that the granting of regulatory clearance will not involve the imposition of additional conditions on the completion of the merger, including the requirement to divest assets, create or modify contractual rights or obligations or enter into supply or services agreements. Any such additional conditions could result in the conditions to the merger not being satisfied.

Quikrete and Summit are working to complete the merger as soon as practicable and currently expect the merger to be completed in the first half of 2025, subject to the satisfaction or waiver of customary closing conditions, including the adoption of the merger agreement by the affirmative vote of at least a majority of the voting power of shares of Summit common stock outstanding and entitled to vote thereon, the expiration or termination of the applicable waiting periods under the HSR Act and the Competition Act (Canada) and receipt of certain other regulatory approvals in respect of radioactive materials licenses indirectly held by Summit. Neither Quikrete nor Summit can predict the actual date on which the merger will be completed because completion is subject to certain closing conditions beyond each party’s control, and it is possible that such conditions could result in the merger being completed earlier or later or not being completed at all. See the sections titled “The Merger Agreement—Efforts to Obtain Regulatory Clearances” and “The Merger Agreement—Conditions to the Merger.” Also, see the section titled “The Merger (Proposal 1)—Regulatory Clearances and Approvals Required for the Merger.”

In addition to the approval of the adoption of the merger agreement in accordance with the DGCL, and the expiration or termination of the waiting periods applicable to the consummation of the merger under the HSR Act and the Competition Act (Canada) and the receipt of certain other regulatory approvals in respect of radioactive materials licenses indirectly held by Summit, each party’s obligation to complete the merger is also subject to the satisfaction or waiver (to the extent permitted under applicable law) of certain other customary conditions, including the following: the absence of any order issued by any court of competent jurisdiction or other governmental authority or applicable law prohibiting, rendering illegal or permanently enjoining the consummation of the merger; the accuracy of the other party’s representations and warranties in the merger agreement (subject to the materiality standards set forth in the merger agreement); compliance by the other party in all material respects with its covenants, obligations and agreements required to be performed or complied with by it under the merger agreement prior to the closing of the merger; and delivery of officer certificates by the other party certifying satisfaction of certain of the conditions described above. The obligation of Quikrete to consummate the merger is also subject to there not having occurred since the date of the merger agreement an event that had or would reasonably be expected to have, individually or in the aggregate, a material adverse effect on Summit. Consummation of the merger is not subject to any financing condition.

See “The Merger Agreement—Conditions to the Merger.”

As more fully described in this proxy statement and in the merger agreement, and subject to certain exceptions, Summit has agreed not to solicit alternative acquisition proposals, engage in discussions with third parties regarding alternative acquisition proposals or change its recommendation in favor of the merger to its stockholders.

In the event Summit receives an unsolicited bona fide written offer, inquiry, proposal or indication of interest from a third party with respect to an acquisition proposal that did not result from a material breach of Summit’s non-solicitation obligations prior to obtaining its stockholders’ approval for the merger agreement proposal and the Summit board of directors determines in good faith that such acquisition proposal constitutes, or would reasonably be expected to lead to, a superior proposal, Summit may provide information to, and engage in discussions and negotiations with, the person making the acquisition proposal, subject to complying with notice requirements and other specified conditions. For more information on what constitutes a superior proposal, see the section titled “The Merger Agreement—No Solicitation of Other Offers by Summit.”

Prior to obtaining approval for the merger agreement proposal from Summit stockholders, the Summit board of directors has the right, in connection with (a) the receipt of a superior proposal or (b) an intervening event to change its recommendation in favor of the merger or, in the case of a superior proposal, to terminate the merger agreement, in each case, subject to complying with notice requirements and other specified conditions (including giving Quikrete the opportunity to propose changes to the merger agreement in response to such superior proposal or intervening event, as applicable), if the Summit board of directors determines in good faith that the failure to take such action would be reasonably expected to be inconsistent with its fiduciary duties under applicable law. For more information on what constitutes an intervening event, see the section titled “The Merger Agreement—Change of Recommendation; Match Rights.”

See “The Merger Agreement—No Solicitation of Other Offers by Summit” and “The Merger Agreement—Change of Recommendation; Match Rights.”

Under the merger agreement, under certain circumstances and subject to certain requirements, including as described in this section, the Summit board of directors is entitled to make an adverse recommendation change prior to receipt of stockholder approval of the merger agreement, if the Summit board of directors determines in good faith, after consultation with its outside legal counsel and financial advisor, that an acquisition proposal constitutes a superior proposal, or in response to an intervening event, if the Summit board of directors determines, after consultation with its outside legal counsel and financial advisor, that the failure to take such action would be reasonably expected to be inconsistent with its fiduciary duties under applicable law; provided that:

In the event that the Summit board of directors is permitted to change its recommendation with respect to the merger agreement following the receipt of an acquisition proposal that it determines to be a superior proposal, Summit may also terminate the merger agreement to enter into a definitive written agreement for such superior proposal if, concurrently with such termination, Summit pays to Quikrete the fee required to be paid to Quikrete as described in the section titled “The Merger Agreement—Termination Fee and Expenses.”

Among other customary circumstances, Quikrete or Summit may terminate the merger agreement if:

Summit may terminate the merger agreement in other circumstances, including to enter into a definitive agreement with respect to a superior proposal or in response to certain breaches of the merger agreement by Quikrete or Merger Sub, subject to a cure period. Quikrete may also terminate the merger agreement in other circumstances, including in response to an adverse recommendation change by the Summit board of directors, a failure to obtain the approval by Summit stockholders to adopt the merger agreement proposal by the outside date or at the special meeting or certain breaches of the merger agreement by Summit, subject to a cure period.

See “The Merger Agreement—Termination of the Merger Agreement.”

Summit must pay Quikrete a termination fee of $279,000,000 if the merger agreement is terminated in certain circumstances, including as a result of Summit entering into a definitive agreement with respect to a superior proposal, an adverse recommendation change, failure to obtain approval by Summit stockholders of the merger agreement proposal by the outside date or at the special meeting or certain breaches of the merger agreement by Summit, subject to a cure period.

See “The Merger Agreement—Termination Fee and Expenses.”

The merger agreement provides that, except in the case of fraud, upon any termination of the merger agreement under circumstances where the termination fee is payable by Summit and such termination fee is paid in full, the receipt by Quikrete of the termination fee will be the sole and exclusive remedy of Quikrete and Merger Sub in connection with the merger agreement or the transactions contemplated thereby, and neither Quikrete nor Merger Sub will seek to obtain any recovery, judgment, or damages of any kind, including consequential, indirect, or punitive damages, against Summit or any of Summit’s subsidiaries or any of their respective directors, officers, employees, partners, managers, members, stockholders, affiliates or representatives in connection with the merger agreement or the transactions contemplated thereby, including any breach of the merger agreement.

See “The Merger Agreement—Remedies; Maximum Liability.”

The merger agreement provides that the parties will be entitled to an injunction or injunctions, or any other appropriate form of equitable relief, to prevent or restrain breaches or threatened breaches of the merger agreement or to enforce specifically the performance of the terms and provisions thereof, without the necessity of proving that irreparable damage would occur or the inadequacy of money damages as a remedy (and each party waived any requirement for the securing or posting of any bond in connection with such remedy), in addition to any other remedy to which they are entitled at law or in equity.

See “The Merger Agreement—Specific Performance.”

Contemporaneously and in connection with the execution of the merger agreement, in their respective capacities as record and beneficial owners of Summit common stock, Cementos Argos S.A., a sociedad anónima incorporated in the Republic of Colombia (“Cementos”), Argos SEM LLC, a Delaware limited liability company (“Argos SEM”) and Valle Cement Investments, Inc., a sociedad anónima incorporated in the Republic of Panama (“Valle Cement” and, together with Cementos and Argos SEM, the “supporting stockholders”) entered into a voting agreement (referred to as the “voting agreement”) with Quikrete, pursuant to which the supporting stockholders agreed, among

other things, to vote their shares of Summit common stock in favor of any proposal to approve the adoption of the merger agreement. In connection with the execution of the voting agreement, Summit waived, to the extent implicated by the execution of the voting agreement or the performance by the supporting stockholders of their obligations thereunder, all restrictions in the stockholder agreement, dated January 12, 2024, among Summit, Cementos, Argos SEM, Valle Cement and, for the limited purposes set forth therein, Grupo Argos S.A. (the “stockholder agreement”) that would restrict the ability of the supporting stockholders to execute the voting agreement and perform their respective obligations thereunder, including a restriction on the supporting stockholders’ ability to vote all of their shares of Summit common stock in favor of the merger agreement proposal. For more information, please see the section of this proxy statement entitled “The Voting Agreement.” For more information regarding the security ownership of the supporting stockholders, please see the section of this proxy statement entitled “Security Ownership of Certain Beneficial Owners and Management.”

Summit stockholders who are entitled to demand and do not vote in favor of approval of the merger agreement proposal, who continuously hold their shares of Summit common stock and who otherwise comply precisely with the applicable provisions of Section 262 of the DGCL will be entitled to seek appraisal of the fair value of their shares of Summit common stock, as determined by the Delaware Court of Chancery, if the merger is completed, in lieu of receiving the merger consideration in respect of such shares. The “fair value” of your shares of Summit common stock as determined by the Delaware Court of Chancery could be greater than, the same as, or less than the value of the merger consideration that you would otherwise be entitled to receive under the terms of the merger agreement. Summit stockholders who wish to exercise the right to seek an appraisal of their shares must so advise Summit by submitting a written demand for appraisal in the form described in this proxy statement prior to the vote to approve the merger agreement proposal, and must otherwise follow the procedures prescribed by Section 262 of the DGCL.

The text of Section 262 of the DGCL is attached as Annex E to this proxy statement. You are encouraged to read these provisions carefully and in their entirety. Due to the complexity of the procedures for exercising appraisal rights, Summit stockholders who are considering exercising such rights are encouraged to seek the advice of legal counsel and their financial advisors. Failure to strictly comply with these provisions may result in the loss of appraisal rights.

See “The Merger Agreement—Effect of the Merger on Summit Common Stock—Shares of Dissenting Stockholders” and “Appraisal Rights of Summit Stockholders.”

At the special meeting, Summit stockholders will be asked to vote upon the following proposals:

The record date for the determination of stockholders entitled to notice of and to vote at the special meeting is [record date]. Only Summit stockholders who held shares of record as of the close of business on the record date are entitled to receive notice of and vote at the special meeting and any adjournment or postponement of the special meeting, and only as long as such shares remain outstanding on the date of the special meeting. Summit’s official stock ownership records will conclusively determine whether a stockholder is a “holder of record” as of the record date.

See “The Special Meeting—Required Vote; Treatment of Abstentions and Failure to Vote.”

Summit’s directors and executive officers have interests in the merger that may be different from, or in addition to, those of Summit stockholders generally. These interests include, among others, vesting of equity awards and potential severance payments and benefits. The Summit board of directors was aware of and considered these interests, among other matters, in evaluating and negotiating the merger agreement and the merger, in approving the merger agreement, and in recommending the approval of the merger agreement by the Summit stockholders. See the section titled “The Merger—Interests of Summit’s Directors and Executive Officers in the Merger” for a more detailed description of these interests.

Under the merger agreement, for a period of six years after the effective time, Quikrete must, and must cause the surviving corporation to, indemnify and hold harmless, to the fullest extent permitted by applicable law and the organizational documents of Summit or its subsidiaries as in effect on the date of the merger agreement, each current and former director and officer of Summit and its subsidiaries and their respective successors and heirs against any losses, damages, liabilities, costs, expenses (including reasonable attorneys’ fees), judgments, fines, penalties and amounts paid in settlement (including all interest, assessments and other charges paid or payable in connection with or in respect of any thereof) in connection with such parties’ having served as a director or officer of Summit prior to the effective time.

In addition, for a period of six years following the effective time, the surviving corporation is required to maintain in effect provisions in the organizational documents of the surviving corporation and its subsidiaries (or in such documents of any successor to the business of the surviving corporation or its subsidiaries) regarding elimination of liability of directors, indemnification of directors, officers, employees, fiduciaries and agents and advancement of fees, costs and expenses that are no less advantageous to the intended beneficiaries than the corresponding provisions that were in existence as of the date of the merger agreement.

Prior to the effective time, (a) Summit will, (b) if Quikrete elects, Quikrete will, or (c) if Summit is unable to, the surviving corporation will (and Quikrete will cause the surviving corporation to) as of the effective time, purchase (and fully pay the premium for) a prepaid, noncancellable directors’ and officers’ liability insurance and fiduciary liability insurance “tail” insurance policy on terms and conditions (in both amount and scope) no less favorable than the current coverage of Summit’s existing policies, which insurance policies will (i) be for a period of six years after the effective time with respect to matters arising at or prior to the effective time, (ii) be from an insurance carrier with the same or better credit rating as Summit’s current insurance carrier with respect to such insurance policies and (iii) have terms, conditions, retentions and limits of liability that are no less favorable than the coverage provided under Summit’s existing policies as of the date of the merger agreement, provided Summit shall not be permitted to pay a premium amount in excess of 300% of the premium amount per annum for Summit’s existing policies for any such extension policy without Quikrete’s prior written consent. If Summit or the surviving corporation for any reason fails to obtain such “tail” insurance policies as of the effective time, the surviving corporation must maintain in effect, for a period of at least six years from the effective time, Summit’s directors’ and officers’ liability insurance and fiduciary liability insurance policies in place as of the date of the merger agreement with Summit’s current

insurance carrier or with an insurance carrier with the same or better credit rating with terms, conditions, retentions and limits of liability that are no less favorable than the coverage provided under the Summit’s existing policies as of the date of the merger agreement, or the surviving corporation must purchase from Summit’s current insurance carrier or from an insurance carrier with the same or better credit rating comparable insurance policies for such six-year period with terms, conditions, retentions and limits of liability that are no less favorable than as provided in Summit’s existing policies as of the date of the merger agreement, provided that in no event must Quikrete or the surviving corporation expend for such policies a premium amount in excess of 300% of the premium amount per annum for Summit’s existing policies, and if the cost of such “tail” insurance policy would otherwise exceed such amount, the surviving corporation must purchase a policy with the greatest coverage available for a cost not exceeding such amount.

See “The Merger (Proposal 1)—Interests of Summit’s Directors and Executive Officers in the Merger—Indemnification and Insurance” and “The Merger Agreement—Directors’ and Officers’ Indemnification and Insurance.”

The merger consideration of $52.50 per share represents a premium of approximately 29.2% over Summit’s unaffected share price (which was the closing price on October 23, 2024, the last trading day prior to the public disclosure of the receipt by Summit of a non-binding acquisition proposal). The closing price of Summit common stock on the New York Stock Exchange (referred to as the “NYSE”) on [•], 2025, the most recent practicable date prior to the date of this proxy statement, was $[•] per share. You are encouraged to obtain current market prices of Summit common stock in connection with voting your shares of Summit common stock.

The following are some questions that you, as a Summit stockholder, may have regarding the merger and the special meeting and the answers to those questions. Summit urges you to carefully read the remainder of this proxy statement because the information in this section does not provide all the information that might be important to you with respect to the merger and the special meeting. Additional important information is also contained in the annexes to and the documents incorporated by reference into this proxy statement.

This proxy statement and the documents incorporated by reference into this proxy statement contain “forward-looking statements” within the meaning of the federal securities laws, which involve risks and uncertainties. Forward-looking statements include all statements that do not relate solely to historical or current facts, and you can identify forward-looking statements because they contain words such as “believes,” “expects,” “may,” “will,” “should,” “seeks,” “intends,” “trends,” “plans,” “estimates,” “projects” or “anticipates” or similar expressions that concern our strategy, plans, expectations or intentions. All statements made relating to our estimated and projected earnings, margins, costs, expenditures, cash flows, growth rates and financial results are forward-looking statements. Such forward-looking statements include but are not limited to statements about the transactions contemplated by the merger agreement, including statements that are not historical facts. These forward-looking statements are subject to risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from future results, performance or achievements expressed or implied by such forward-looking statements. We derive many of our forward-looking statements from our operating budgets and forecasts, which are based upon many detailed assumptions. While we believe that our assumptions are reasonable, it is very difficult to predict the effect of known factors, and, of course, it is impossible to anticipate all factors that could affect our actual results. In light of the significant uncertainties inherent in the forward-looking statements included herein, the inclusion of such information should not be regarded as a representation by us or any other person that the results or conditions described in such statements or our objectives and plans will be realized. Important factors could affect our results and could cause results to differ materially from those expressed in our forward-looking statements, including but not limited to the factors discussed in the section entitled “Risk Factors” in Summit’s Annual Report on Form 10-K for the fiscal year ended December 30, 2023, and Quarterly Report on Form 10-Q for the fiscal quarter ended March 30, 2024, each as filed with the SEC, and any factors discussed in the section entitled “Risk Factors” in any of our subsequently filed SEC filings; and the following: (i) the occurrence of any event, change, or other circumstance that could give rise to the right of one or both of the parties to terminate the merger agreement, including in circumstances requiring Summit to pay a termination fee; (ii) potential litigation relating to the merger that could be instituted against the parties to the merger agreement or their respective directors or officers, including the effects of any outcomes related thereto; (iii) the possibility that the merger does not close when expected or at all because required regulatory, shareholder, or other approvals and other conditions to closing are not received or satisfied on a timely basis or at all; (iv) reputational risk and potential adverse reactions of customers, employees or other business partners and the businesses generally, including those resulting from the announcement of the merger; (v) the risk that any announcements relating to the merger could have adverse effects on the market price of Summit’s common stock; (vi) significant transaction costs associated with the merger; and (vii) the diversion of management’s attention and time from ongoing business operations and opportunities on merger-related matters.

All subsequent written and oral forward-looking statements attributable to us, or persons acting on our behalf, contained or incorporated by reference in this proxy statement and all subsequent written and oral forward-looking statements concerning Summit, the merger or other matters attributable to Summit or any person acting on its behalf are expressly qualified in their entirety by the cautionary statement above. Any forward-looking statement that we make herein speaks only as of the date of this proxy statement. We undertake no obligation to publicly update or revise any forward-looking statement as a result of new information, future events or otherwise, except as required by law.

If any of these risks materialize or any of Summit’s assumptions prove incorrect, actual results could differ materially from the results implied by these forward-looking statements. There may be additional risks that Summit presently does not know of or that Summit currently believes are immaterial that could also cause actual results to differ from those contained in the forward-looking statements. These forward-looking statements should not be relied upon as representing Summit’s assessments as of any date subsequent to the date of this proxy statement. Accordingly, undue reliance should not be placed upon the forward-looking statements.

Summit is a market-leading producer of aggregates and cement with vertically integrated operations that supply ready-mix concrete and asphalt in select markets. Summit is a geographically diverse, materials-led business of scale that offers customers in the United States and British Columbia, Canada high quality products and services for the public infrastructure, residential and non-residential end markets. Summit has a strong track record of successful acquisitions since its founding and continues to pursue high-return growth opportunities in new and existing markets. Summit Materials, Inc. was formed under the laws of the State of Delaware on September 23, 2014. The principal executive office of Summit is located at 1801 California Street, Suite 3500, Denver, Colorado 80202, and its telephone number is (303) 893-0012.

Quikrete is a privately owned family business founded in 1940. It is a leading building materials company based in Atlanta, Georgia. From the original yellow bag of premixed concrete, today Quikrete’s portfolio of brands includes Quikrete, Spec Mix, Rinker Materials, U.S. Pipe, Contech Engineered Solutions, Keystone Hardscapes, Pavestone, Custom Building Products, QPR, and other leading brands. The products produced by the collection of brands include packaged cementitious products, pavers, retaining wall systems, masonry units, tile grouts and thin sets, concrete pipe, box culverts, corrugated metal pipe, ductile iron pipe, engineered storm water systems, structural precast, and steel pedestrian and vehicular bridges. The company services the United States and Canadian commercial construction, residential, and infrastructure markets. This broad array of products and expertise allows Quikrete to provide nearly every product required for most any type of construction project. The principal executive offices of Quikrete are located at 5 Concourse Parkway, Suite 1900, Atlanta, GA 30328, and its telephone number is (404) 634-9100.

Merger Sub is a wholly owned subsidiary of Quikrete. Merger Sub was incorporated by Quikrete solely in contemplation of the transactions contemplated by the merger agreement, has not conducted any business and has no assets, liabilities or obligations of any nature other than as set forth in the merger agreement. The principal executive offices of Merger Sub are located at c/o Quikrete Holdings, Inc., 5 Concourse Parkway, Suite 1900, Atlanta, GA 30328, and its telephone number is (404) 634-9100.

This proxy statement is first being mailed on or about [mailing date], 2025 and constitutes notice of the special meeting in conformity with the requirements of the DGCL and Summit’s bylaws.

This proxy statement is being provided to Summit stockholders as part of a solicitation of proxies by the Summit board of directors for use at the special meeting of Summit stockholders and at any adjournments or postponements of such special meeting. This proxy statement provides Summit stockholders with information about the special meeting and should be read carefully in its entirety.

The special meeting will be held on [•], 2025, beginning at [•], Mountain Time, unless postponed to a later date, at Summit’s principal executive offices at 1801 California St, Ste. 3500 Denver, CO 80202.

At the special meeting, Summit stockholders will be asked to vote upon the following proposals:

Only the approval of the merger agreement proposal is required for completion of the merger. Summit will transact no other business at the special meeting except such business as may properly be brought before the special meeting or any adjournment or postponement thereof.

At a special meeting held on November 24, 2024, the Summit board of directors unanimously determined that the merger agreement and the transactions contemplated thereby are advisable, fair to and in the best interests of Summit and its stockholders, approved the execution of the merger agreement and the consummation of the transactions contemplated thereby, and directed that the adoption of the merger agreement be submitted to a vote at a meeting of the Summit stockholders.

Accordingly, the Summit board of directors unanimously recommends that Summit stockholders vote “FOR” the merger agreement proposal, “FOR” the merger-related compensation proposal and “FOR” the adjournment proposal.

Summit stockholders should carefully read this proxy statement, including any documents incorporated by reference, and the annexes in their entirety for more detailed information concerning the merger and the transactions contemplated by the merger agreement.

As of the record date, there were [•] shares of Summit Class A common stock outstanding and owned by Summit stockholders (i.e., excluding shares of Summit common stock held in treasury by Summit), held by [•] holders of record. As of the record date, there were no shares of Summit Class B common stock outstanding. As of the record

date, there was one share of Summit preferred stock outstanding. Holders of shares of Summit preferred stock are not entitled to vote on any matter considered at the special meeting. Each share of Summit Class A common stock is entitled to one vote on each matter considered at the special meeting.

Stockholders may request an appointment to inspect a complete list of stockholders entitled to vote at the special meeting for any purpose germane to the special meeting at Summit’s principal executive offices located at 1801 California St, Ste. 3500 Denver, CO 80202, during ordinary business hours within 10 days prior to the special meeting. This list will also be made available at the special meeting for examination by any stockholder present at the special meeting.

The record date for the determination of stockholders entitled to notice of and to vote at the special meeting is [record date]. Only holders of Summit common stock as of the close of business on the record date are entitled to receive notice of, and vote at, the special meeting or any adjournment or postponement thereof. Summit’s official stock ownership records will conclusively determine whether a stockholder is a “holder of record” as of the record date.

Holders of a majority of the voting power of the issued and outstanding shares of Summit common stock as of the record date and entitled to vote at the special meeting must be present or represented by proxy at the special meeting to constitute a quorum for the transaction of business at the special meeting. If you fail to submit a proxy or to vote at the special meeting, or fail to instruct your bank, brokerage firm or other nominee how to vote, your shares of Summit common stock will not be counted towards a quorum. Marks to “ABSTAIN” on any proposal are considered present for purposes of establishing a quorum. In the event that a quorum is not present at the special meeting, it is expected that the special meeting will be adjourned or postponed. If the special meeting is postponed or adjourned, it will not affect the ability of holders of record of Summit common stock as of the record date to exercise their voting rights or to revoke any previously granted proxy using the methods described below; however, if a new record date is set for an adjourned meeting, a new quorum will be required to be established. As noted above, pursuant to the voting agreement and subject to the terms and conditions thereof, the supporting stockholders have agreed, among other things, to be represented in person or by proxy at the special meeting in order for the shares of Summit common stock held by the supporting stockholders to be counted as present for purposes of establishing a quorum.

Banks, brokerage firms and other nominees who hold shares in “street name” for the accounts of their clients may vote such shares either as directed by their clients or in their own discretion on “routine” matters. When a broker does not receive instructions from a beneficial owner on how to vote shares with respect to a “non-routine” matter, a “broker non-vote” occurs. “Broker non-votes” will not be treated as present for purposes of determining whether a quorum is present. All proposals described in this proxy statement to be voted on at the special meeting are considered “non-routine” matters.

Your shares will be counted for purposes of determining if there is a quorum, whether representing votes for, against or abstained, if you (1) participate in the special meeting or (2) have voted via the internet, by telephone or by properly submitting a proxy card or voting instruction card by mail.

The votes required for each proposal are as follows:

Proposal 1—The Merger Agreement Proposal: The affirmative vote of holders of at least a majority of the voting power of shares of Summit common stock outstanding and entitled to vote thereon is required to approve the merger agreement proposal. If you mark “ABSTAIN” on your proxy, it will have the same effect as a vote “AGAINST” the merger agreement proposal. If you fail to submit a proxy or to vote at the special meeting or fail to instruct your bank, brokerage firm or other nominee how to with respect to the merger agreement proposal, it will have the same effect as a vote “AGAINST” the merger agreement proposal.

Pursuant to the voting agreement and subject to the terms and conditions thereof, the supporting stockholders have agreed, among other things, to vote their shares of Summit common stock in favor of the proposal to approve the adoption of the merger agreement. Summit waived, to the extent implicated by the execution of the voting agreement or the performance by the supporting stockholders of their obligations thereunder, all restrictions in the stockholder agreement that would restrict the ability of the supporting stockholders to execute the voting agreement

and perform their respective obligations thereunder, including a restriction on the supporting stockholders’ ability to vote all of their shares of Summit common stock in favor of the merger agreement proposal. For more information, please see the section of this proxy statement entitled “The Voting Agreement.” For more information regarding the security ownership of the supporting stockholders, please see the section of this proxy statement entitled “Security Ownership of Certain Beneficial Owners and Management.”

Proposal 2—The Merger-Related Compensation Proposal: The affirmative vote of holders of at least a majority of the voting power of shares of Summit common stock present or represented by proxy at the special meeting and entitled to vote thereon is required to approve, on an advisory (non-binding) basis, the merger-related compensation proposal. If you mark “ABSTAIN” on your proxy, it will have the same effect as a vote “AGAINST” the merger-related compensation proposal. If you fail to submit a proxy or to vote at the special meeting or fail to instruct your bank, brokerage firm or other nominee how to with respect to the merger-related compensation proposal, it will have no effect on the merger-related compensation proposal (assuming a quorum is present).

Proposal 3—The Adjournment Proposal: The affirmative vote of holders of at least a majority of the voting power of shares of Summit common stock present or represented by proxy at the special meeting and entitled to vote thereon is required to approve the adjournment proposal, including if necessary to solicit additional proxies for the adoption of the merger agreement. If you mark “ABSTAIN” on your proxy, it will have the same effect as a vote “AGAINST” the adjournment proposal. If you fail to submit a proxy or to vote at the special meeting or fail instruct your bank, brokerage firm or other nominee how to vote with respect to the adjournment proposal, it will have no effect on the adjournment proposal.

An abstention occurs when a stockholder attends a meeting but abstains from voting. At the special meeting, abstentions will be counted in determining whether a quorum is present and will have the effect of a vote “AGAINST” the merger agreement proposal, the merger-related compensation proposal and the adjournment proposal, including if necessary to permit further solicitation of proxies.

If you are a registered stockholder and you do not sign and return your proxy card by mail or vote over the internet, by telephone or by attendance at the special meeting, your shares will not be voted at the special meeting and will not be counted for purposes of determining whether a quorum exists. If you are the record owner of your shares and you fail to vote, it will have the same effect as a vote “AGAINST” the merger agreement proposal but will have no effect on the outcome of the adjournment proposal or merger-related compensation proposal.

As of the record date, Summit directors and executive officers, as a group, owned and were entitled to vote [•] shares of Summit common stock, or approximately [•]% of the outstanding shares of Summit common stock. Summit currently expects that these directors and executive officers will vote their shares in favor of the merger agreement proposal and each of the other proposals described in this proxy statement, although, except as set forth below with respect to the voting agreement, none of the directors and executive officers are obligated to do so.

As noted above, pursuant to the voting agreement and subject to the terms and conditions thereof, the supporting stockholders have agreed, among other things, to vote their shares of Summit common stock in favor of the proposal to approve the adoption of the merger agreement. Summit waived, to the extent implicated by the execution of the voting agreement or the performance by the supporting stockholders of their obligations thereunder, all restrictions in the stockholder agreement that would restrict the ability of the supporting stockholders to execute the voting agreement and perform their respective obligations thereunder, including a restriction on the supporting stockholders’ ability to vote all of their shares of Summit common stock in favor of the merger agreement proposal. For more information, please see the section of this proxy statement entitled “The Voting Agreement.” For more information regarding the security ownership of the supporting stockholders, please see the section of this proxy statement entitled “Security Ownership of Certain Beneficial Owners and Management.”

Summit stockholders of record may vote their shares of Summit common stock at the special meeting or submit a proxy to have their shares of Summit common stock voted at the special meeting in one of the following ways:

Whether or not you plan to participate in the special meeting, Summit urges you to submit your proxy by completing and returning the proxy card as promptly as possible, or by submitting your proxy by telephone or via the internet, prior to the special meeting to ensure that your shares of Summit common stock will be represented and voted at the special meeting if you are unable to participate.

The Summit board of directors has appointed certain persons as proxy holders to vote proxies in accordance with the instructions of Summit stockholders. If you are a stockholder of record and you authorize these proxy holders to vote your shares of Summit common stock with respect to any matter to be acted upon, your shares will be voted in accordance with your instructions in your proxy. If you are a stockholder of record and you authorize these proxy holders to vote your shares but do not specify how your shares should be voted on a proposal, these proxy holders will vote your shares on such proposals as the Summit board of directors recommends. If any other matter properly comes before the special meeting, these proxy holders will vote on that matter in their discretion.

If, as of the record date, your shares of Summit common stock are registered directly in your name with the transfer agent of Summit, Broadridge, you are considered the stockholder of record with respect to those shares. As the stockholder of record, you have the right to vote or to grant a proxy for your vote directly to Summit or to a third party to vote at the special meeting.

If, as of the record date, your shares were held in an account at a bank, brokerage firm or other nominee, you are the beneficial owner of shares held in “street name,” and, for the purposes of this proxy statement, a beneficial owner, and your bank, brokerage firm or other nominee is considered the stockholder of record with respect to those shares. If you are a beneficial owner, you have a right to direct your bank, brokerage firm or other nominee on how to vote the shares held in your account. The availability of internet or telephonic voting will depend on the nominee’s voting process. Please check with your bank, brokerage firm or other nominee and follow the voting procedures your bank, brokerage firm or other nominee provides.

In accordance with the rules of the NYSE, your bank, brokerage firm or other nominee may generally vote on “routine” matters when they have not received voting instructions from you. However, such banks, brokerage firms and other nominees are precluded from exercising their voting discretion with respect to “non-routine” matters. If you are a beneficial owner and do not provide these instructions, a “non-vote” occurs with respect to those matters. All proposals described in this proxy statement to be voted on at the special meeting are considered “non-routine” matters. Accordingly, if you are a beneficial owner and do not provide your bank, brokerage firm or other nominee instructions on how to vote your shares of Summit common stock, your bank, brokerage firm or other nominee generally will not be permitted to vote your shares on any of the proposals. The effect of not instructing your broker how you wish your shares to be voted will be the same as a vote “AGAINST” the merger agreement proposal but will not have an effect on the adjournment proposal or the merger-related compensation proposal (assuming, in the case of the merger-related compensation proposal, a quorum is present). If you are a beneficial holder, Summit strongly encourages you to provide voting instructions to your bank, brokerage firm or other nominee so that your vote will be counted on all matters.

If you are a beneficial owner, you are invited to participate in the special meeting; however, you may not vote your shares at the special meeting unless you obtain a “legal proxy” from your bank, brokerage firm or other nominee that holds your shares, giving you the right to vote the shares at the special meeting.

Summit stockholders of record may revoke their proxies at any time prior to the voting at the special meeting in any of the following ways:

Summit beneficial owners may change their voting instruction only by following the directions received from their bank, brokerage firm or other nominee for changing their voting instructions.

As permitted by applicable law, only one copy of this proxy statement is being delivered to holders of Summit common stock residing at the same address, unless such holders of Summit common stock have notified Summit of their desire to receive multiple copies of this proxy statement.

Summit will promptly deliver, upon oral or written request, a separate copy of this proxy statement to any holder of Summit common stock residing at an address to which only one copy of this proxy statement was mailed. Requests for additional copies should be directed by mail to Summit’s Executive Vice President, Chief Legal Officer & Secretary, at Summit Materials, Inc., 1801 California Street, Suite 3500, Denver, Colorado 80202, or by telephone to (303) 893-0012, or to Summit’s proxy solicitor, Georgeson LLC (referred to as “Georgeson”), by calling toll-free at (888) 755-6840 or by email at summitmaterials@georgeson.com.

If your shares are held by your broker, bank or other nominee, often referred to as held in “street name,” you will receive a form from your broker, bank or other nominee seeking instruction as to how your shares should be voted. You should contact your broker, bank or other nominee with questions about how to provide or revoke your instructions.

A representative from Broadridge will serve as the inspector of election.

Summit will pay for the proxy solicitation costs related to the special meeting. In addition to sending and making available these materials, some of Summit’s directors, officers and employees may solicit proxies in person by contacting Summit stockholders by telephone or over the Internet. Summit stockholders may also be solicited by press releases issued by Summit, postings on Summit’s website and advertisements in periodicals. None of Summit’s directors, officers or employees will receive additional compensation for their solicitation services. Summit has engaged Georgeson to assist in the solicitation of proxies for the special meeting. Summit estimates that it will pay Georgeson a fee of approximately $25,000, plus reasonable out-of-pocket expenses relating to the special meeting. Certain banking institutions, brokerage firms, custodians, trustees, nominees and fiduciaries who hold shares for the benefit of another party may solicit proxies for Summit. If so, they will mail proxy information to, or otherwise communicate with, the beneficial owners of shares of Summit common stock held by them. Summit will also reimburse banks, brokerage firms, custodians, trustees, nominees and fiduciaries for their expenses incurred in sending proxies and proxy materials to beneficial owners of Summit common stock.

The special meeting may be adjourned by the affirmative vote of at least a majority of the voting power of shares of Summit common stock present or represented by proxy at the special meeting and entitled to vote thereat, provided that there is not a quorum present.

Notice need not be given of any adjourned meeting if the time and place, if any, thereof and the means of remote communications, if any, by which stockholders and proxy holders may be deemed to be present in person or represented by proxy and vote at such adjourned meeting are (a) announced at the meeting at which the adjournment is taken, (b) displayed during the time scheduled for the meeting, on the same electronic network used to enable stockholders and proxy holders to participate in the meeting by means of remote communication or (c) set forth in the notice of meeting given in accordance with Summit’s bylaws. If the adjournment is for more than 30 days, a notice of the adjourned meeting will be given to each stockholder of record entitled to vote at the meeting. If, after any adjournment, a new record date for the determination of stockholders entitled to vote is fixed for any adjourned meeting, the Summit board of directors shall fix as the record date for determining stockholders entitled to notice of such adjourned meeting the same or an earlier date as that fixed for determination of stockholders entitled to vote at the adjourned meeting, and shall give notice of the adjourned meeting to each stockholder of record entitled to vote at such adjourned meeting as of the record date so fixed for notice of such adjourned meeting.

You may contact Summit’s proxy solicitor, Georgeson, toll-free at (888) 755-6840 or by email at summitmaterials@georgeson.com, with any questions about the special meeting, the merger, the proposals or this proxy statement, if you would like additional copies of this proxy statement, if you need to obtain proxy cards or other information related to the proxy solicitation or if you need help submitting a proxy or voting your shares of Summit common stock.

This section of this proxy statement describes the material aspects of the merger. This section may not contain all of the information that is important to you. You should carefully read this entire proxy statement and the documents incorporated by reference into this proxy statement, including the full text of the merger agreement, a copy of which is attached to this proxy statement as Annex A, for a more complete understanding of the merger. In addition, important information about Summit is included in or incorporated by reference into this proxy statement. See the section titled “Where You Can Find More Information.”

Upon the terms and subject to the conditions of the merger agreement and in accordance with Delaware law, Merger Sub will merge with and into Summit, whereupon the separate existence of Merger Sub will cease and Summit will survive the merger as a wholly owned subsidiary of Quikrete.

The following diagrams illustrate in simplified terms the merger and the effect of the merger on the organizational structures of Quikrete and Summit.

The following diagram illustrates in simplified terms the organizational structure of Quikrete and Summit prior to the merger:

The following diagram illustrates in simplified terms the merger:

The following diagram illustrates in simplified terms the organizational structure of Quikrete and Summit after the merger:

If the merger agreement is not adopted by Summit stockholders or if the merger is not completed for any other reason, Summit stockholders will not receive any payment for their shares (or interests in shares) of Summit common stock in connection with the merger. Instead, Summit will remain an independent public company, Summit common stock will continue to be listed and traded on the NYSE and registered under the Exchange Act and we will continue to file periodic reports with the SEC. In addition, if the merger is not completed, Summit stockholders will continue to be subject to the same risks and opportunities to which they are currently subject, including risks related to the highly competitive industry in which Summit operates and risks related to adverse economic conditions.

Furthermore, if the merger is not completed, and depending on the circumstances that would have caused the merger not to be completed, it is likely that the price of Summit common stock will decline significantly. If that were to occur, it is uncertain when, if ever, the price of Summit common stock would return to the price at which it trades as of the date of this proxy statement.

Accordingly, if the merger is not completed, there can be no assurance as to the effect of these risks and opportunities on the future value of your shares of Summit common stock. If the merger agreement is not adopted by Summit stockholders or if the merger is not completed for any other reason, there can be no assurance that any other transaction acceptable to Summit will be offered or that Summit’s business, prospects or results of operation will not be adversely impacted.

In addition, the merger agreement provides that, upon termination of the merger agreement under certain circumstances, Summit will be required to pay to Quikrete a termination fee of $279,000,000 under the terms of the merger agreement. See the section titled “The Merger Agreement—Termination Fee and Expenses” for a discussion of the circumstances under which such termination fee would be required to be paid.

At the effective time, each share of Summit common stock issued and outstanding immediately prior to the effective time (other than (a) excluded shares and (b) dissenting shares) will be converted into the right to receive the merger consideration of $52.50 in cash, without interest and subject to deduction for any required withholding. Each share of Summit preferred stock outstanding immediately prior to the effective time will automatically be canceled and retired for no consideration and will cease to exist.

The following chronology summarizes the key meetings and events that led to the signing of the merger agreement. This chronology does not purport to catalogue every conversation of or among the Summit board of directors, Quikrete, Summit’s representatives, Quikrete’s representatives and other parties.

The Summit board of directors and senior management regularly review and assess Summit’s operations, performance, opportunities, prospects and strategic direction. In connection with this review and assessment, and with the assistance of legal and financial advisors, the Summit board of directors and management have considered potential strategic alternatives for Summit, including potential business combinations or other transactions, to strengthen Summit’s business and maximize shareholder value. For example, on January 12, 2024, Summit completed a transaction with Argos North America Corp. (“Argos North America”), Cementos, Argos SEM and Valle Cement, pursuant to which Summit acquired all of the outstanding equity interests of Argos North America. In addition, Summit has from time to time received unsolicited inquiries from third parties seeking to determine Summit’s interest in a variety of potential M&A transactions.

On September 19, 2024, an individual at Wells Fargo Bank, N.A. (“Wells Fargo”) contacted Howard L. Lance, the Chairman and Director of the Summit board of directors, to inform Mr. Lance that a representative of Quikrete, a client of Wells Fargo, had expressed an interest in speaking with him.

On September 25, 2024, Mr. Lance met with William R. Magill, the Chief Executive Officer of Quikrete, in Atlanta, Georgia. Mr. Magill informed Mr. Lance that Quikrete was interested in a potential acquisition of Summit and relayed that Quikrete was prepared to submit a formal proposal to acquire Summit for $48.00 per share in cash. Mr. Lance informed Mr. Magill that Summit was not seeking to engage in a merger or a sale of Summit at that time and that the Summit board of directors was optimistic about Summit’s standalone strategy and its prospects in the near and long-term, but, consistent with Summit’s practice and the Summit board of directors’ fiduciary duties, if the Summit board of directors were presented with an offer, the Summit board of directors would review the offer to determine if it was in the best interests of Summit and its stockholders. Mr. Lance and Mr. Magill discussed the proposed all-cash deal and their views on the potential antitrust implications of a transaction between Quikrete and Summit.

Later that same day, Quikrete provided to Mr. Lance an initial non-binding proposal to acquire Summit for $48.00 per share in cash (referred to as the “first Quikrete offer”) with no financing contingency along with a highly confident letter from Wells Fargo, a list of due diligence requests and an initial draft mutual confidentiality agreement, which included customary non-disclosure provisions and a six-month standstill arrangement. The standstill provision included language specifying that the provision would terminate automatically in the event that (i) any person or group acquired or entered into a definitive agreement to acquire, or the Summit board of directors approved the acquisition of, the majority of any class of equity securities of Summit or its subsidiaries, or assets of Summit or its subsidiaries representing more than 25% of the consolidated earning power of Summit and its subsidiaries, (ii) Summit initiated any bankruptcy or insolvency proceedings or (iii) a third party publicly announced a proposal regarding the acquisition of the majority of any class of equity securities of Summit or its subsidiaries, or assets of Summit or its subsidiaries representing more than 25% of the consolidated earning power of Summit and its subsidiaries.

Later that same day, Mr. Lance discussed the proposal with representatives of Davis Polk, counsel to Summit, including potential next steps.

On October 1, 2024, Mr. Lance informed the Summit board of directors of the terms of the first Quikrete offer. He also noted that a Summit board of directors meeting to discuss the first Quikrete offer would be set for October 7, 2024.

On October 3, 2024, Mr. Lance and representatives of Davis Polk met, in separate meetings, with representatives of Morgan Stanley and Evercore, in New York City to discuss their views on the first Quikrete offer. Starting in May 2021, Mr. Lance periodically sought the perspectives of Morgan Stanley, Summit’s financial advisor in connection with Summit’s acquisition of Argos North America, given Morgan Stanley’s qualifications, experience and reputation and its knowledge of Summit’s businesses and the industries in which Summit operates, regarding potential acquisitions and other strategic alternatives that Summit might consider to enhance stockholder value. Evercore, based on its qualifications, reputation, knowledge and experience of Summit’s businesses and the industries in which Summit operates, had several discussions with Summit’s management and board of directors. In addition, since September 2023, Mr. Lance and the Summit board of directors periodically sought Evercore’s perspectives on a broad range of value creation and other strategic alternatives for Summit to enhance stockholder value, including but not limited to investor receptivity in connection with Summit’s acquisition of Argos North America.

On October 4, 2024, Davis Polk received a relationship disclosure letter from Morgan Stanley, detailing certain relationships involving Morgan Stanley and Quikrete.

Also on October 4, 2024, a representative of Davis Polk had a phone conversation with a representative from Sullivan & Cromwell LLP (“Sullivan & Cromwell”), legal counsel to Cementos, regarding (i) the right of Cementos under the stockholder agreement to participate as a potential acquiror on the same terms as any prospective third-party acquiror if Summit were to engage in any sale process or negotiations relating to a potential change of control transaction and (ii) the participation of the members of the Summit board of directors nominated by Cementos in the upcoming meeting of the Summit board of directors to discuss the first Quikrete offer. Sullivan & Cromwell communicated that Cementos had not determined whether it would participate in any potential sale process as a potential acquiror, and Davis Polk and Sullivan & Cromwell agreed that each of Mr. Jorge Mario Velásquez, the President and Chief Executive Officer of Grupo Argos S.A., Mr. Juan Esteban Calle, Chief Executive Officer of Cementos, and Ms. Irene Moshouris, an independent director nominated to the Summit board of directors by Cementos, would depart the meeting of the Summit board of directors after the general terms of the first Quikrete offer were presented and the Summit board of directors was briefed on its fiduciary duties and would not participate during the presentations from Summit’s financial advisors, except with respect to factual aspects of the first Quikrete offer, or the deliberations of the Summit board of directors regarding the first Quikrete offer.

On October 7, 2024, the Summit board of directors held a meeting to discuss the first Quikrete offer. Members of management and representatives of Davis Polk, Morgan Stanley and Evercore were present at the meeting. Mr. Lance described his discussion with Mr. Magill and the first Quikrete offer. He then presented several key considerations to the Summit board of directors relating to the first Quikrete offer and reviewed potential strategic alternatives, including in relation to the Summit board of directors’ obligations to Cementos and certain of its affiliates under the stockholder agreement. Mr. Lance noted for the Summit board of directors that Summit was required to inform Cementos of the first Quikrete offer and to provide Cementos with an opportunity to participate in the potential sale process on the same terms as other potential counterparties. Representatives of Davis Polk and the Executive Vice President, Chief Legal Officer and Secretary of Summit discussed the terms of the first Quikrete offer. Davis Polk then delivered a presentation to the Summit board of directors summarizing the Summit board of directors’ fiduciary duties and legal obligations in the context of a potential sale process and with respect to the right of Cementos to participate in any such process. Representatives of Davis Polk then presented a preliminary review of regulatory considerations in connection with a potential transaction with Quikrete. Representatives of Morgan Stanley and Evercore discussed factual information regarding the financial aspects of the first Quikrete offer. Because Cementos had not determined whether it desired to participate in any potential sale process as a potential acquiror, the members of the Summit board of directors designated by Cementos under the stockholder agreement, Messrs. Calle and Velásquez and Ms. Moshouris, departed the meeting. The directors who were not designated by Cementos remained to evaluate the first Quikrete offer and consider next steps. Representatives of Morgan Stanley discussed certain preliminary perspectives regarding the first Quikrete offer and noted, among other things, that the proposed purchase price of $48.00 per share exceeded Summit’s all-time high share price at that time. Representatives of Morgan Stanley also discussed certain financing-related risks and the debt financing letter that Quikrete had provided with the first Quikrete offer. Representatives of Evercore then discussed, among other things, Evercore’s initial analysis of the first Quikrete offer and Evercore’s preliminary views as to the value of Summit based on a number of valuation methodologies. The discussions from Morgan Stanley and Evercore were conducted separately, with representatives of each advisor departing the meeting for the other advisor’s discussion.

At the same meeting, following these discussions, Mr. Lance reiterated to the Summit board of directors that the Summit board of directors’ obligation in connection with a potential sale transaction was to maximize value for Summit’s stockholders. The Summit board of directors continued to discuss the first Quikrete offer, and areas where they believed Summit needed more information to fully evaluate the first Quikrete offer. The Summit board of directors then discussed whether to engage with other parties who, taking into account discussions with Morgan Stanley and Evercore, the Summit board of directors believed to be most likely to be able to provide a viable competing proposal. After further discussion, the Summit board of directors (without the Cementos designated directors) unanimously determined that the first Quikrete offer did not provide sufficient value to Summit’s stockholders and therefore it was not advisable or in the best interests of Summit’s stockholders to provide non-public information to Quikrete. The directors, however, viewed the first Quikrete offer as serious and instructed Mr. Lance and Summit’s advisors to continue discussions with Quikrete, and to solicit additional information regarding Quikrete’s potential financing arrangements. The Summit board of directors also approved engaging Morgan Stanley and Evercore as financial advisors to Summit in connection with the potential sale process. The Summit board of directors instructed Davis Polk to prepare a notice to Cementos in accordance with Summit’s obligations under the stockholder agreement. In addition, the Summit board of directors instructed Mr. Lance to relay to Quikrete that the

Summit board of directors had concluded that the first Quikrete proposal did not provide Summit stockholders with sufficient value and therefore the Summit board of directors was not willing to provide non-public information to Quikrete. Later that day, Summit delivered to Cementos a written notice that the board of directors determined that it was in the best interests of Summit for Summit to engage in discussions with one or more potential bidders relating to a potential change of control transaction, that, pursuant to the stockholder agreement, Cementos would be entitled to participate in such discussions on the same terms as other bidders if it delivers written notice of its intent to do so within 15 business days, and that the Cementos designated directors should continue to recuse themselves from any meetings of the Summit board of directors or any committees thereof regarding such discussions until such time as Cementos confirms that it will not participate as a potential acquiror in a process for a potential change of control transaction with Summit.

On October 9, 2024, Davis Polk received a relationship disclosure letter from Evercore, detailing certain relationships involving Evercore and Quikrete.

On October 10, 2024, Mr. Lance informed Mr. Magill via a phone call that while Summit appreciated the first Quikrete offer, the Summit board of directors had concluded that it did not provide Summit stockholders with sufficient value, and therefore the Summit board of directors was not willing to provide non-public information to Quikrete. In addition, Mr. Lance indicated that the Summit board of directors wanted to better understand Quikrete’s financing structure and that he had asked Morgan Stanley and Evercore to initiate discussions with Wells Fargo.

Between October 10, 2024 and October 14, 2024, Mr. Lance had multiple phone calls with Mr. Magill regarding Quikrete’s desire to acquire Summit during which Mr. Lance encouraged Mr. Magill to offer additional value to Summit’s stockholders. On October 10, 2024, Mr. Magill indicated that Quikrete might be willing to increase its $48.00 per share offer price by approximately 5%. On October 11, 2024, Mr. Magill indicated that Quikrete might be willing to increase its $48.00 per share offer price to $50.00 per share.

On October 14, 2024, following the aforementioned discussions over the phone between Mr. Lance and Mr. Magill, Quikrete submitted a second proposal to Mr. Lance (referred to as the “second Quikrete offer”), which increased the proposed purchase price from $48.00 to $50.00 per share. Mr. Lance promptly shared the second Quikrete offer with the Summit board of directors and scheduled a meeting of the Summit board of directors on October 21, 2024 to discuss.

The second Quikrete offer had no financing contingency and included a post-signing go-shop period of two weeks with a termination fee equal to 1% of equity value during such two-week period, which termination fee would automatically increase to 3% of equity value after such two-week period. As part of the second Quikrete offer, Quikrete provided a draft exclusivity agreement with a proposed 45-day exclusivity period along with a highly confident letter from Wells Fargo. The second Quikrete offer stated that the definitive agreement would contain customary provisions for a transaction of this type, including representations and warranties, interim operating covenants, closing conditions and termination provisions, including a customary termination fee payable by Summit in the event that the definitive agreement is terminated under certain circumstances and a “reasonable and balanced approach to the terms in the definitive agreement related to any antitrust matters.” This proposal also stated that Quikrete’s counsel was prepared to deliver a draft of the definitive agreement promptly upon Summit’s execution of an exclusivity agreement.

Between October 15, 2024 and October 16, 2024, Mr. Lance had multiple phone calls with Mr. Magill regarding Quikrete’s desire to acquire Summit.

On October 16, 2024, representatives of Morgan Stanley and Evercore discussed with representatives of Wells Fargo the anticipated financing for the transaction.

On October 17, 2024, a representative of Davis Polk had a phone conversation with representatives from Sullivan & Cromwell regarding Cementos’ views with respect to a potential transaction. Sullivan & Cromwell indicated that Cementos had not yet decided whether to participate as a potential acquiror in a process for a potential change of control transaction with Summit. Representatives of Sullivan & Cromwell asked the Davis Polk representative for a status update with respect to the proposed transaction with Quikrete, and the Davis Polk representative responded that the Summit board of directors was evaluating next steps.

On October 19, 2024, a representative of Davis Polk had a phone conversation with a representative from Sullivan & Cromwell, who informed the representative of Davis Polk that Cementos did not intend to participate as a potential acquiror in a process for a potential change of control transaction with Summit.

On October 21, 2024, the Summit board of directors (including the members of the Summit board of directors designated by Cementos under the Stockholders Agreement) held a meeting to discuss the second Quikrete offer. The Executive Vice President, Chief Legal Officer and Secretary of Summit and representatives of Davis Polk, Morgan Stanley and Evercore were present. Mr. Lance relayed that following recent discussions with Cementos, Cementos determined not to be a bidder in connection with the potential transaction. Mr. Lance then discussed his recent phone calls with Mr. Magill regarding Quikrete’s desire to acquire Summit. Mr. Lance described the key terms of the second Quikrete offer. Mr. Lance also explained that, as authorized by the Summit board of directors at its prior meeting, Morgan Stanley and Evercore had engaged in discussions with Wells Fargo to better understand Wells Fargo’s financing of Quikrete’s acquisition. The Executive Vice President, Chief Legal Officer and Secretary of Summit and a Davis Polk representative next described the risk of public disclosures of information relating to the potential transaction and the need to develop potential response plans. The Summit board of directors and representatives of Davis Polk, Morgan Stanley, Evercore and management discussed the second Quikrete offer and the potential transaction further and potential next steps. Morgan Stanley then discussed with the Summit board of directors preliminary financial information and data regarding Summit and the second Quikrete offer. Evercore then presented to the Summit board of directors and discussed Evercore’s preliminary valuations, as well as a peer group comparison, public trading multiples, precedent transactions and discounted cash flow analysis. The discussions from Morgan Stanley and Evercore were conducted separately, with representatives of each advisor departing the meeting for the other advisor’s discussion. After discussion, the Summit board of directors unanimously determined that, while the second Quikrete offer did not provide sufficient value to Summit’s stockholders to proceed with the proposed transaction or enter into an exclusivity agreement with Quikrete, it did warrant further engagement. The Summit board of directors authorized its financial advisors to communicate this to Quikrete and, subject to entering into a customary confidentiality agreement, to share limited information and engage in discussions with Quikrete on a non-exclusive basis to enable Quikrete to better understand the potential value of Summit, including potential synergy opportunities in connection with a transaction and relating to the acquisition of Argos North America, and to determine if Quikrete could improve the second Quikrete offer. During the same meeting, the Summit board of directors discussed Summit’s performance and five-year plan and reviewed the assumptions reflected in the five-year plan by business segment. Members of the Summit board of directors and management then discussed certain historical information and recent changes and growth opportunities, following which the Summit board of directors approved the five-year plan.

On October 22, 2024, Mr. Lance informed Mr. Magill via phone call that while Summit appreciated the second Quikrete offer, the Summit board of directors had concluded that the second Quikrete offer did not provide sufficient value to Summit’s stockholders to proceed with a transaction. However, subject to entering into a customary confidentiality agreement, Summit would be willing to share limited information and engage in discussions with Quikrete on a non-exclusive basis to enable Quikrete to determine if it could improve its proposed offer. On October 23, 2024, representatives of Morgan Stanley and Evercore reiterated the Summit board of directors’ feedback to representatives of Wells Fargo and discussed potential limited due diligence access.

Also on October 23, 2024, Davis Polk sent Troutman Pepper Hamilton Sanders LLP (“Troutman”), legal counsel to Quikrete, a revised draft of the mutual confidentiality agreement that had initially been received by Summit on September 25, 2024.

On October 24, 2024, Davis Polk received an updated draft of the mutual confidentiality agreement from Troutman. The primary areas of disagreement in the mutual confidentiality agreement related to the scope of the non-solicitation and standstill obligations that would be binding on Quikrete and certain exclusivity arrangements that Troutman had incorporated in the latest draft.

Later on October 24, 2024, Bloomberg published a news article reporting that Summit was considering a proposed transaction with Quikrete. The article described the proposed purchase price as being in the “low 50s.” Several other news publications followed, which assessed Summit’s value in a sale transaction as ranging from approximately $47.00 to approximately $60.00 per share. Later on October 24, 2024, Mr. Lance and Mr. Magill had a conversation over the phone to discuss the Bloomberg article. Mr. Lance advised Mr. Magill that Summit expected to issue a press release confirming receipt of the proposal from Quikrete and confirmed to Mr. Magill that Summit continued to be open to continuing discussions regarding the proposed transaction. Mr. Lance reiterated to Mr. Magill that Quikrete would need to increase its proposed purchase price for an agreement to be reached. Mr. Magill stated that Quikrete’s preference was to accelerate the timeline to enter into the proposed transaction.

Later on October 24, 2024, Mr. Lance informed the Board of the news article.

Later in the evening of October 24, 2024, Summit released a statement confirming that Summit had held preliminary discussions with a third party regarding a potential transaction and that Summit was actively evaluating the proposal in consultation with its advisors.

Following the public disclosure of Quikrete’s proposal to acquire Summit, over the course of the October 24, 2024 and October 25, 2024, Summit’s common stock price increased approximately 11% from closing at $40.62 on October 23, 2024 to closing at $45.10 on October 25, 2024.

Following the public disclosure of Quikrete’s proposal to acquire Summit, Morgan Stanley and Evercore received inbound communications from other parties interested in a potential transaction with Summit. On October 25, 2024, Evercore received an inbound communication from a possible strategic party (“Strategic Party A”), a publicly traded company. Also on October 25, 2024, Morgan Stanley received an inbound communication from another possible strategic party (“Strategic Party B”), a publicly traded company, asking for information on the ongoing sale process with Quikrete. Also on October 25, 2024, Morgan Stanley and Evercore received separate inbound communications from another possible strategic party (“Strategic Party C”), a publicly traded company, stating that Strategic Party C was not interested in acquiring all of the equity of Summit but would be interested in acquiring certain assets of Summit.

Also on October 25, 2024, Davis Polk sent a further revised draft of the mutual confidentiality agreement to Troutman. Having no further areas of disagreement, Quikrete and Summit executed the mutual confidentiality agreement on October 25, 2024, which ultimately included a one-year standstill provision that terminates automatically if (i) any person or group acquires or enters into a definitive agreement to acquire, or the Summit board of directors approves the acquisition of, the majority of each class of equity securities of Summit, or assets of Summit or its subsidiaries representing a majority of the consolidated earning power of Summit and its subsidiaries or (ii) Summit initiates any bankruptcy or insolvency proceedings. The mutual confidentiality agreement provided Quikrete the ability to make offers on a confidential basis to Summit that would not reasonably be expected to require a public announcement or disclosure by Summit or any of its representatives. The mutual confidentiality agreement also included customary mutual obligations to preserve the confidentiality of information exchanged and did not provide for any exclusivity arrangements. Following execution of the confidentiality agreement, the financial advisors of Summit regularly engaged with Wells Fargo on Quikrete’s limited due diligence review.

On October 26, 2024, Mr. Lance, the President and Chief Executive Officer of Summit, the Executive Vice President, Chief Legal Officer and Secretary of Summit, and Summit’s legal and financial advisors held a phone call to discuss proposed outreach to other potential bidders. Morgan Stanley and Evercore advised Mr. Lance that Mr. Lance and the President and Chief Executive Officer of Summit should initiate conversations with certain parties to discuss a potential transaction with Summit. Morgan Stanley and Evercore suggested that Summit indicate a willingness to sign confidentiality agreements and provide confidential information to potentially interested parties while seeking preliminary proposals based on public information. Mr. Lance and Summit’s legal and financial advisors discussed potential candidates for outreach, including both potential strategic counterparties and financial sponsors. Representatives of Morgan Stanley and Evercore advised that the economic terms that may be offered by financial sponsors likely would not be as favorable to Summit’s stockholders as the economic terms that strategic parties may be willing to offer. The participants in this phone call ultimately determined to contact Strategic Party A, Strategic Party B and two additional public company strategic parties (“Strategic Party D” and “Strategic Party E”). Morgan Stanley and Evercore also noted that any other interested party could make their interest known following the Summit October 25, 2024 press release. Shortly after the conclusion of the phone call, Mr. Lance contacted representatives of Strategic Party A, Strategic Party B, Strategic Party D and Strategic Party E to encourage them to submit a proposal if they were interested in an acquisition of, or combination with, Summit.

On October 27, 2024, Mr. Lance received a phone call from Mr. Velásquez, the President and Chief Executive Officer of Grupo Argos S.A. Mr. Lance and Mr. Velásquez discussed the potential sale of Summit to Quikrete. Mr. Velásquez emphasized the potential value to Summit involved in near-shoring aggregates to selected United States markets and the importance of ensuring this value is reflected in any potential transaction. Mr. Velásquez also emphasized the importance of conducting competitive outreach to maximize price to all stockholders with respect to any sale of Summit. After Mr. Lance explained the outreach process to other potential transaction partners, Mr. Velásquez indicated that he was satisfied with Summit’s efforts to date. Lastly, Messrs. Lance and Velásquez discussed the perspective of Cementos in its capacity as a stockholder on a potential transaction with Quikrete, and in that context Mr. Velásquez reiterated to Mr. Lance the strategic importance to Cementos of maintaining its economic exposure to the United States cement and aggregates markets, noting that Cementos had expected its

investment to be long-term. Mr. Velásquez noted that, based on discussions at a recent meeting of Cementos’ board of directors, it appeared that Cementos in its capacity as a stockholder would have a difficult time supporting any transaction that eliminated its exposure to the United States cement and aggregates markets and prevented it from re-deploying any proceeds from a sale of Summit back into such markets.

On October 28, 2024, the Chief Executive Officer of Strategic Party D called Mr. Lance and confirmed that a rumor that Strategic Party D planned to submit a competing bid to acquire Summit was unfounded. The Chief Executive Officer of Strategic Party D conveyed that Strategic Party D did not intend to make a proposal to acquire Summit and cited considerations including competing strategic priorities.

On October 29, 2024, Mr. Lance reached out to representatives of Strategic Party B regarding a potential transaction with Summit.

Also on October 29, 2024, representatives of Morgan Stanley and Evercore had a discussion with a representative of Strategic Party A, who expressed Strategic Party A’s desire to continue communication regarding a potential transaction. The representative of Strategic Party A expressed that it was important to Strategic Party A that any potential transaction would be friendly and there be unanimity at the Summit board of directors on the desire to engage. The representative of Strategic Party A understood that time was of the essence.

Later on October 29, 2024, Mr. Lance spoke with the Chairman of Strategic Party A, who relayed Strategic Party A’s interest in a potential transaction with Summit. Mr. Lance shared Summit’s timeline for a potential transaction. Following this discussion, Mr. Lance confirmed that the Summit board of directors authorized Morgan Stanley and Evercore to engage in discussions with Strategic Party A in respect of a potential transaction.

Also on October 29, 2024, Troutman sent Davis Polk a proposed initial draft merger agreement for a transaction between Quikrete and Summit. The draft contemplated that Summit’s largest stockholder, Cementos, would enter into a voting agreement with Quikrete to vote its shares in Summit in favor of the merger. Representatives of Davis Polk and Summit determined that Summit would not engage with the draft from Troutman in light of the fact that Summit intended to simultaneously engage with alternative potential acquirors using a merger agreement that had been prepared by Summit and Davis Polk for all potential bidders, including Quikrete.

Also on October 29, 2024, Morgan Stanley and Evercore spoke with a representative of Strategic Party B about the process. The representative of Strategic Party B requested that their regulatory counsel be connected with Davis Polk to discuss regulatory matters.

On October 30, 2024, Davis Polk informed Troutman of its view that it was premature to engage in negotiations on the merger agreement until Quikrete had submitted a revised proposal that the Summit board of directors deemed to be in the best interests of Quikrete or its stockholders, and that any initial transaction document would be based on a form prepared by Davis Polk given the potential involvement of other parties.

Later on October 30, 2024, representatives of Davis Polk held a call with Strategic Party B’s legal advisor in respect of a potential transaction with Strategic Party B. The parties discussed the potential regulatory implications of a transaction between Strategic Party B and Summit and considerations related to conducting a preliminary regulatory analysis.

On October 31, 2024, Morgan Stanley and Evercore inquired with representatives of Strategic Party A on the status of its review of a potential transaction with Summit, and Strategic Party A confirmed that it was continuing to review.

On November 1, 2024, Evercore received a call from the President and Chief Executive Officer of another possible strategic party (“Strategic Party G”), who stated that Strategic Party G was aware that a process concerning Summit was underway and that Strategic Party G planned to hold a meeting of its board of directors in the near term to discuss a potential transaction with Summit.

Also on November 1, 2024, Morgan Stanley and Evercore inquired with representatives of Strategic Party B on the status of its preliminary regulatory analysis.

Also on November 1, 2024, Evercore received a call from a possible financial party (“Financial Party A”) which expressed interest in a potential transaction with Summit and inquired as to whether any strategic party was looking for a partner.

Later on November 1, 2024, Morgan Stanley discussed with a representative of Strategic Party E, who stated that Strategic Party E was actively evaluating a potential transaction with Summit, but that no conclusion had been reached. The representative of Strategic Party E expressed that Strategic Party E had a strong understanding of Summit’s assets and acknowledged that there had been helpful dialogue between Strategic Party E and Summit over the years. Morgan Stanley reiterated that (i) Strategic Party E’s interest is welcome, (ii) time is of the essence and (iii) the channel of communications remains open.

On November 2, 2024, Davis Polk sent its own draft merger agreement to Troutman, requesting that Quikrete include with its updated proposal on November 8, 2024 a revised draft of the merger agreement or list of legal issues.

Later on November 2, 2024, Davis Polk sent an initial form confidentiality agreement and clean team agreement to a representative of Strategic Party B.

On November 4, 2024, Summit and representatives of Morgan Stanley and Evercore hosted representatives of Quikrete and Wells Fargo for a management presentation, which covered (i) an overview of Summit’s organization and operations, (ii) an update regarding Summit’s integration of Argos North America, (iii) an overview of Summit’s business plan and (iv) a summary of potential benefits of an acquisition of Summit by Quikrete.

On November 5, 2024, Mr. Lance spoke with a representative of Strategic Party E, who informed Mr. Lance that Strategic Party E declined to participate in a process for a potential transaction with Summit. The representative of Strategic Party E did not provide Strategic Party E’s rationale for this decision.

Also on November 5, 2024, Morgan Stanley and Evercore again inquired with representatives of Strategic Party A on the status of its review of a potential transaction with Summit, and Strategic Party A again confirmed that it was continuing to review.

Also on November 5, 2024, Morgan Stanley and Evercore discussed with a representative of Strategic Party B to confirm that Strategic Party B and its legal advisor still intended to discuss the proposed transaction, and particularly the regulatory implications thereof, with Davis Polk the following day. Morgan Stanley and Evercore requested that Strategic Party B enter into a confidentiality agreement prior to the meeting between Davis Polk and Strategic Party B’s legal advisor, to which the representative of Strategic Party B responded that a confidentiality agreement would only be necessary prior to the sharing of confidential information between the parties. A representative of Davis Polk confirmed that the call could proceed without a confidentiality agreement on a counsel-to-counsel basis.

On November 6, 2024, representatives of Davis Polk discussed with representatives of Strategic Party B’s legal advisor the potential regulatory implications of a transaction between Strategic Party B and Summit.

Also on November 6, 2024, Evercore received communication from a representative of Strategic Party A outlining that they would be working with a partner on an acquisition structure and wanted to know whether this structure would be competitive. Evercore noted that the Summit board of directors would evaluate any proposal provided regardless of the structure or type of consideration. Strategic Party A represented it was familiar with Summit’s assets and that they would structure the acquisition such that Strategic Party A would divest all of Summit’s cement assets, once acquired, to their partner.

Also on November 6, 2024, representatives of Davis Polk spoke with representatives of Sullivan & Cromwell regarding the status of the sale process. Representatives of Davis Polk informed representatives of Sullivan & Cromwell that they expected that the ultimate buyer would likely request a voting agreement from Cementos as a condition to entering into the transaction, and representatives of Sullivan & Cromwell responded by emphasizing the strategic importance to Cementos and its board of directors of exposure to the United States cement and aggregates markets and that Cementos would have a difficult time supporting any transaction as a stockholder, with or without a voting agreement, that eliminated its exposure to and precluded Cementos from re-entering these markets.

On November 7, 2024, Morgan Stanley delivered to Davis Polk its updated relationship disclosure letter, detailing certain relationships involving Morgan Stanley and each of Quikrete, Strategic Party A and Strategic Party B.

Also November 7, 2024, Mr. Lance had a phone call with a representative of Strategic Party G, who requested additional information regarding Summit’s ongoing sale process in advance of a meeting of the board of directors of Strategic Party G later that day. In response to questions from the representative of Strategic Party G, Mr. Lance stated that (i) the Summit board of directors would evaluate any proposal provided by Strategic Party G or any other parties,

regardless of the proposed structure or type of consideration, based on the value that would be delivered to Summit’s stockholders and the certainty and timeline of the transaction and (ii) Strategic Party G should submit a letter of intent prior to the next meeting of the Summit board of directors on November 13, 2024.

Also on November 7, 2024, Evercore received a communication from Financial Party A asking for information on timing and the ongoing sale process with Quikrete. Financial Party A indicated that they were working with a strategic partner which was not disclosed but understood to be Strategic Party A. Financial Party A indicated that in its proposed structure it would acquire the cement assets of Summit and that their partner would acquire the remaining businesses.

On November 8, 2024, Morgan Stanley and Evercore received communication from Strategic Party B that they had received feedback from the counsel-to-counsel session and were completing their analysis based on that feedback.

Also November 8, 2024, Mr. Lance had another conversation with Mr. Magill, who noted that Quikrete would send a revised letter of intent and financing commitment letter later that day. Mr. Magill also stated that a revised version of Davis Polk’s initial draft merger agreement would be provided to Davis Polk shortly, and that the revised draft would be generally consistent with the parties’ prior discussions. Mr. Magill stated that the offer price would be $51.50 per share in cash, which Quikrete considered to be a “best and final” offer price. The price represented an approximately 50% premium to the price at the time of Cementos’ investment in Summit and an approximately 35% premium to Summit’s undisturbed 90-day volume weighted average price at the time of Quikrete’s initial proposal. Mr. Magill stated that the offer did not have an expiration date, but that Quikrete likely would not move forward if Summit did not commit to an exclusivity period by the end of the following week or soon thereafter. Mr. Magill stated that Quikrete desired to sign definitive agreements and announce the transaction before Thanksgiving.

Later on November 8, 2024, Wells Fargo sent Summit’s financial advisors a revised offer (referred to as the “third Quikrete offer”), which included: (i) a revised draft of the merger agreement along with a list of key issues for negotiation, (ii) a revised offer letter from Quikrete explaining its proposal in more detail, including a reaffirmation of its proposed purchase price of $51.50 per share, (iii) a debt financing commitment letter from Wells Fargo and (iv) an updated draft exclusivity letter, which contemplated a ten-day exclusivity period. The revised offer package reiterated Quikrete’s desire that Cementos would enter into a voting agreement.

On November 9, 2024, representatives of Morgan Stanley spoke with representatives of Strategic Party B to encourage Strategic Party B to participate in the potential sale process.

On November 10, 2024, Mr. Lance had a phone call with Mr. Velásquez, who posed questions about the value being offered by Quikrete. Mr. Velásquez requested to speak with Quikrete’s management to discuss Quikrete’s desire for Cementos to enter into a voting agreement. Mr. Lance explained that Mr. Velásquez would have an opportunity to speak with Quikrete’s management after Summit’s next Summit board of directors meeting. Mr. Lance advised Davis Polk that prior to the upcoming meeting of the Summit board of directors, he would like to schedule a call between Messrs. Velásquez and Calle and Summit’s financial advisors to discuss the proposed transaction with Quikrete.

Also November 10, 2024, representatives of Financial Party A informed representatives of Evercore that they had been in communications with their partner (understood to be Strategic Party A) on deal structure and that the decision to pursue the acquisition was under the consideration of their prospective partner.

On November 11, 2024, Davis Polk received an updated relationship disclosure letter from Evercore, detailing certain relationships involving Evercore and each of Quikrete, Strategic Party A and Strategic Party B.

Also on November 11, 2024, a representative of Strategic Party A informed Mr. Lance that Strategic Party A declined to participate in a process for a potential transaction with Summit, noting that Strategic Party A concluded that it would be very challenging to provide a compelling proposal, both from a value perspective and an execution certainty perspective.

On November 11, 2024, representatives of Morgan Stanley and Evercore spoke with a representative of Strategic Party G, who informed Morgan Stanley and Evercore that Strategic Party G determined not to submit an offer to acquire Summit ahead of the upcoming Summit board of directors meeting, citing that it would be challenging for Strategic Party G to participate in the current process.

On November 12, 2024, a representative of Strategic Party B informed Morgan Stanley and Evercore that Strategic Party B would not be submitting a bid to acquire Summit, citing that they did not expect to be in a position to make a compelling proposal at such time.

On November 13, 2024, the Summit board of directors held a meeting to discuss the ongoing negotiations with Quikrete, including with respect to the key terms of the latest draft merger agreement, as well as the ongoing solicitation of other potential bidders. The Executive Vice President, Chief Legal Officer and Secretary of Summit and representatives of Davis Polk, Morgan Stanley and Evercore were present. A Davis Polk representative and the Executive Vice President, Chief Legal Officer and Secretary of Summit provided an overview of the material terms of the latest draft merger agreement being negotiated with Quikrete, including the proposed price of $51.50 per share in cash with no financing contingency, and certain covenants in the agreement relating to obtaining required regulatory approvals. Representatives of Davis Polk also discussed Davis Polk’s ongoing review of the potential regulatory analysis. Representatives of Morgan Stanley next provided an overview of updates since the previous meeting of the Summit board of directors, discussed certain preliminary financial information and data regarding Summit and provided an update on the ongoing diligence process with Quikrete. The members of the Summit board of directors and representatives of Morgan Stanley engaged in further discussions regarding the proposed $51.50 per share cash purchase price and possible strategies designed to induce Quikrete to further increase its proposed price. Following further deliberation and advice from Morgan Stanley, it was the consensus of the directors that although the proposed price of $51.50 per share was value maximizing when taking into account Summit’s financial forecast and prospects and the status of the market check process, Quikrete likely would be willing to increase its proposed price. Following this discussion, representatives of Evercore summarized their views as to the third Quikrete offer, including key economic terms, timing, diligence and other considerations. Representatives of Evercore also provided an overview of Summit’s earnings performance relative to peer companies and an analysis of the macroeconomic environment for M&A activity. Evercore relayed that it was of the view that Quikrete likely would be willing to increase its price in response to a counter from Summit. The discussions from Morgan Stanley and Evercore were conducted separately, with representatives of each advisor departing the meeting for the other advisor’s discussion. Taking into account the discussions with each of Morgan Stanley and Evercore, the directors unanimously agreed that Mr. Lance should engage in further negotiations with Mr. Magill and respond with a counterproposal of $52.50 per share in cash. The directors also authorized Mr. Lance and management to grant Quikrete up to 10 days of exclusivity on customary terms and conditions if Quikrete were to agree in principle to that price.

At the same meeting of the Summit board of directors, Mr. Lance provided an overview of his discussions with the Chief Executive Officer of Quikrete regarding Quikrete’s requirement that Summit’s largest stockholder, Cementos, enter into a voting agreement with Quikrete to vote its shares in Summit in favor of the merger. Mr. Velásquez noted that, in his capacity as a director of Summit, he was fully supportive of pursuing a transaction with Quikrete consistent with the discussions that occurred earlier in the meeting. Mr. Velásquez then shared the perspectives of Cementos and its board of directors with respect to the potential transaction with Quikrete. Mr. Velásquez provided an overview of Cementos’ presence in the United States market over the last half century and Cementos’ strategic rationale for its sale of Argos North America to Summit in 2023 in exchange for its current equity position in Summit, including the goal of having a long-term investment providing Cementos exposure to the United States market in the form of its current equity position in Summit. As a result, in light of the proposed transaction, Cementos was grappling with its long-term strategy in the United States and concerns that the sale would eliminate its investment exposure in the United States market with Cementos being limited in its ability to re-invest in the United States due to the non-competition provisions in the existing restrictive covenant agreement that was entered into in connection with the sale of Argos North America to Summit, which in the view of Cementos were unduly restrictive and not necessary in a situation where Cementos no longer held an equity position (or had board representation) in Summit. Accordingly, Cementos felt it was very important to be able to have a conversation with Quikrete following a final agreement on price between Summit and Quikrete regarding relief from the restrictive covenant agreement in light of the request from Quikrete for a voting agreement from Cementos. Mr. Velásquez confirmed that Cementos was not looking to otherwise change the terms of any other commercial arrangements between Cementos and Summit in connection with entering into the voting agreement. Following the conclusion of Mr. Velásquez’s comments, a Davis Polk representative explained to the Summit board of directors that, should the Summit board of directors permit a conversation between Quikrete and Cementos to occur, that conversation should only take place if, and when, Summit and Quikrete had an agreement on the per share transaction value. The Cementos designated directors, Messrs. Calle and Velásquez and Ms. Moshouris, then left the meeting and the remaining directors engaged in a discussion regarding, among other matters, the request from Quikrete for a voting

agreement and Cementos’ intention to request relief from Quikrete of the restrictive covenant agreement. Following conclusion of the discussion, the remaining directors determined that should Summit and Quikrete reach agreement on price, Cementos could engage in a discussion with Quikrete (including Mr. Lance) regarding a voting agreement and a waiver of the non-compete provisions contained in the restrictive covenant agreement.

On November 13, 2024, Mr. Lance told Mr. Magill that the Summit board of directors wanted Quikrete to further increase its proposed purchase price to a price of $52.50 per share. Later on November 13, 2024, Mr. Magill called Mr. Lance and stated that he was surprised by the Summit board of directors’ request and had expected Summit to accept Quikrete’s previous offer of $51.50. However, Mr. Magill stated that he would be comfortable increasing Quikrete’s proposal to $52.00 per share. Mr. Lance responded with a counterproposal of $52.50 per share, to which Mr. Magill verbally agreed.

On November 14, 2024, Davis Polk reached out to Sullivan & Cromwell via phone to notify them of the informal agreement on the $52.50 per share price between Mr. Magill and Mr. Lance and to inform them that the parties were now targeting a signing and announcement of the proposed transaction on the morning of November 25, 2024. Davis Polk informed Sullivan & Cromwell that Quikrete’s proposal was conditioned on Cementos entering into a voting agreement in respect of the proposed transaction. Davis Polk and Sullivan & Cromwell then discussed certain proposed terms of the voting agreement.

Also on November 14, 2024, Troutman shared with Davis Polk an initial draft of the voting agreement and, per Troutman’s request, Davis Polk introduced Troutman to Sullivan & Cromwell to discuss voting agreement matters. Pursuant to the draft voting agreement, the Cementos-affiliated stockholders would be required, among other things, to vote their shares in favor of the adoption of the merger agreement and not acquire additional shares. Later on November 14, 2024, Davis Polk discussed the voting agreement with Troutman and Davis Polk provided initial feedback, including that (i) Summit should not be a party to the voting agreement, (ii) the voting agreement should terminate upon a change in board recommendation and (iii) the voting agreement should allow the directors affiliated with Cementos to exercise their fiduciary duties.

On November 15, 2024, Summit and Quikrete executed an exclusivity letter, pursuant to which Summit agreed to negotiate exclusively with Quikrete until November 25, 2024.

Also on November 15, 2024, a representative of Strategic Party E contacted Mr. Lance to inform him that, notwithstanding Strategic Party E’s previous confirmation that it was declining to participate in a process for a potential transaction with Summit, Strategic Party E was still considering a potential transaction with Summit and intended to submit a letter of interest.

Also on November 15, 2024, (i) Davis Polk sent Troutman a revised draft of the merger agreement and (ii) Troutman sent a revised draft of the voting agreement to Davis Polk and Sullivan & Cromwell.

On November 17, 2024, representatives of Davis Polk and Sullivan & Cromwell had a phone call to discuss the potential transaction and the requested voting agreement. The representatives of Sullivan & Cromwell and Davis Polk also discussed the possibility of Quikrete waiving the non-competition and other related provisions under the existing restrictive covenant agreement in connection with and conditioned on the closing of the proposed transaction.

Also on November 17, 2024, Davis Polk sent a revised draft of the voting agreement to Sullivan & Cromwell.

On November 18, 2024, a representative of Strategic Party E contacted Mr. Lance to confirm that it would not participate in a process for a potential transaction with Summit.

Also on November 18, 2024, Troutman sent Davis Polk a revised draft of the merger agreement.

Also on November 18, 2024, Sullivan & Cromwell sent a revised draft of the voting agreement to Davis Polk, which provided, among other matters, that on the terms and subject to the conditions described therein, the supporting stockholders would vote their shares of Summit common stock in favor of any proposal to adopt the merger agreement with Quikrete subject to the limitation in the stockholder agreement requiring the supporting shareholders to vote all shares representing more than 25.01% of the outstanding voting power of Summit common stock in the same proportion of all other votes cast on the matter (the “25.01% limitation”) and that the non-competition and certain related provisions of the existing restrictive covenant agreement would no longer be in effect following the closing of the proposed transaction. Sullivan & Cromwell also noted that they expected to receive a response regarding their proposal on the restrictive covenant agreement prior to a dinner meeting among Messrs. Lance, Magill and Velásquez scheduled for November 19, 2024.

On November 19, 2024, Troutman shared a revised draft of the voting agreement with Davis Polk and Sullivan & Cromwell, which reflected, among other matters, that Summit would waive the 25.01% limitation, that the supporting stockholders would vote all of their shares of Summit common stock in favor of the transaction, and that, subject to certain conditions, the non-competition and certain related provisions of the existing restrictive covenant agreement would no longer be in effect following the closing of the proposed transaction.

Also on November 19, 2024, Mr. Lance attended a dinner with Mr. Magill and Mr. Velásquez. At the dinner, the parties discussed several matters relating to the treatment of Summit’s equity awards, other employment-related matters, and certain regulatory-related covenants under the merger agreement. Mr. Magill also confirmed that, subject to receipt of a voting agreement from Cementos, Quikrete was willing to terminate the non-compete covenants in the restrictive covenant agreement effective at the closing of the transaction. After discussion, Mr. Velásquez agreed to support the execution of a voting agreement in favor of a proposed transaction with Quikrete.

Between November 19, 2024 and November 22, 2024, representatives of Sullivan & Cromwell and Troutman exchanged drafts and negotiated the terms of the voting agreement. Key terms negotiated between the parties included: (i) whether Summit would waive the 25.01% limitation, (ii) the circumstances in which the voting agreement would terminate; and (iii) conditions to the waiver immediately after closing of the non-competition and certain related provisions under the restrictive covenant agreement.

On November 20, 2024, Davis Polk sent Troutman a further revised draft of the merger agreement.

On November 21, 2024, The Wall Street Journal published an article stating that Quikrete was in advanced talks to buy Summit. Summit’s stock rose in value, presumably in response to this news article.

On November 22, 2024, Evercore delivered to Davis Polk its final updated relationship disclosure letter, detailing certain relationships involving Evercore and Quikrete.

On November 22, 2024, Troutman sent Davis Polk a further revised draft of the merger agreement. The parties continued to exchange drafts of the merger agreement between November 22, 2024 and November 24, 2024.

On November 22, 2024, representatives of Davis Polk, Sullivan & Cromwell, Troutman and Quikrete held a call to discuss the voting agreement. To proceed with the transaction, Quikrete relayed its insistence that Summit waive the 25.01% limitation.

On November 23, 2024, Messrs. Lance, Velásquez and Calle spoke to discuss the terms of the voting agreement that Mr. Magill had indicated was necessary for Quikrete to proceed with the transaction. Mr. Lance informed Messrs. Velásquez and Calle that, as requested by Quikrete, the Summit board of directors would waive the 25.01% limitation to enable the supporting stockholders to agree to vote all of their shares of Summit common stock in favor of any proposal to approve the merger agreement with Quikrete. After discussion, Messrs. Velásquez and Calle agreed in principle to enter into a voting agreement with the waiver of the 25.01% limitation, as requested by Quikrete. Following the call, Troutman sent a revised draft of the voting agreement to Davis Polk and Sullivan & Cromwell, which reflected the waiver of the 25.01% limitation.

On November 24, 2024, the Summit board of directors held a meeting to evaluate the terms and conditions of the proposed transaction with Quikrete and to determine whether to approve the proposed transaction. Members of management and representatives of Davis Polk, Morgan Stanley and Evercore were present. Mr. Lance explained that the Summit board of directors would be receiving updated analyses of the proposed transaction from Summit’s financial advisors, including an evaluation of the proposed purchase price from a financial perspective, to allow the Summit board of directors to make an informed decision as to whether the merger was in the best interests of Summit and its stockholders. Representatives of Davis Polk, among other things, provided an overview of the Summit board of directors’ fiduciary duties under Delaware law in the context of the sale of Summit, reviewed the process that Summit had undertaken since the time of its receipt of the first Quikrete offer, and provided an overview of the terms of the merger agreement. Summit’s Executive Vice President, Chief People and ESG Officer and Head of Communications then walked through the communications plan, including employee communications and the approach for responding to questions related to the proposed transaction.

During the same meeting of the Summit board of directors, Morgan Stanley reviewed and discussed its financial analyses with respect to the proposed merger. Thereafter, at the request of the Summit board of directors, Morgan Stanley rendered its oral opinion to the Summit board of directors (which was subsequently confirmed in writing by delivery of Morgan Stanley’s written opinion dated the same date) as to, as of November 24, 2024 and subject to the

various assumptions made, procedures followed, matters considered, and qualifications and limitations on the review undertaken by Morgan Stanley as set forth in its written opinion, the fairness, from a financial point of view, to the holders of Summit’s common stock of the merger consideration to be received by such holders in the merger pursuant to the merger agreement. Following the presentation from Morgan Stanley, Evercore reviewed and discussed with the Summit board of directors its financial analysis of the proposed merger consideration and at the request of the Summit board of directors, Evercore rendered its oral opinion to the effect that, as of that date and based upon and subject to the analyses, procedures, assumptions, limitations, qualifications and conditions described in Evercore’s opinion, the merger consideration of $52.50 in cash per share to be received by the holders of Summit common stock in the merger was fair, from a financial point of view, to such holders (other than Quikrete or any subsidiary of Quikrete, Summit or any subsidiary of Summit, or holders of dissenting shares), which was subsequently confirmed in writing by delivery of Evercore’s written opinion dated the same date. The presentations from Morgan Stanley and Evercore were conducted separately, with representatives of each advisor departing the meeting for the other advisor’s presentation.

During the same meeting of the Summit board of directors, representatives of Davis Polk and the members of the Summit board of directors discussed the Summit board of directors’ intention to approve the transaction for purposes of Section 203 of the DGCL. Representatives of Davis Polk and the members of the Summit board of directors also discussed the terms of the voting agreement, including Quikrete’s request to waive the 25.01% limitation, and Quikrete’s proposed waiver of the non-competition and other related provisions applicable to the supporting stockholders under the existing restrictive covenant agreement. Following these discussions, the Summit board of directors took two votes on the proposed transaction. On the first vote, the members of the Summit board of directors designated by Cementos under the stockholders agreement, Messrs. Calle and Velásquez and Ms. Moshouris, abstained in light of the voting agreement. Upon motion duly made and seconded, all of the remaining directors (i) determined that it is in the best interests of Summit and its stockholders, and declared it advisable, that Summit enter into the merger agreement and consummate the transactions contemplated thereby, (ii) approved and declared advisable the execution and delivery of the merger agreement and the consummation of the transactions contemplated thereby, including the merger, and (iii) directed that the merger agreement and the transactions contemplated thereby be submitted for consideration by the stockholders of Summit entitled to vote thereon at a meeting thereof. Thereafter, upon motion duly made and seconded, all of the members of the Summit board of directors unanimously took the actions referenced in (i) through (iii) above.

On November 24, 2024, following the meeting of the Summit board of directors, representatives of Davis Polk delivered written notice to Sullivan & Cromwell on behalf of Cementos and the other supporting stockholders that Summit had waived, effective as of the execution of the merger agreement and the voting agreement, and solely to the extent implicated by the execution and delivery of the voting agreement or the performance by the supporting stockholders of their obligations thereunder, all restrictions in the stockholder agreement that would restrict the ability of the supporting stockholders to execute and deliver the voting agreement and perform their respective obligations thereunder, including the 25.01% limitation.

On November 24, 2024, Summit and Quikrete entered into the merger agreement and Quikrete and the supporting stockholders entered into the voting agreement. Before the opening of NYSE normal trading hours on November 25, 2024, Summit and Quikrete issued a joint press release announcing the execution of the merger agreement.

At its November 24, 2024 meeting held to evaluate the merger, the Summit board of directors unanimously (i) determined that it is in the best interests of Summit and its stockholders, and declared it advisable, that Summit enter into the merger agreement and consummate the transactions contemplated thereby, (ii) approved and declared advisable the execution and delivery of the merger agreement and the consummation of the transactions contemplated thereby, including the merger, and (iii) directed that the merger agreement and the transactions contemplated thereby be submitted for consideration by Summit stockholders entitled to vote thereon at a meeting thereof. The Summit board of directors recommends that Summit stockholders vote:

In evaluating the merger agreement and arriving at its determination, the Summit board of directors consulted with Summit’s senior management, representatives of each of Summit’s financial advisors, Morgan Stanley and Evercore, and Summit’s outside legal counsel, Davis Polk, and considered a number of substantive factors, both positive and negative, and potential benefits and detriments of the merger to Summit and Summit stockholders. The Summit board of directors believed that, taken as a whole, the following factors supported its decision to approve the merger:

The Summit board of directors also considered certain potentially negative factors in its deliberations concerning the merger, including the following:

The Summit board of directors concluded that the potentially negative factors associated with the merger were significantly outweighed by the potential benefits that it expected the Summit stockholders would achieve as a result of the merger. The Summit board of directors believed that the merger would maximize the immediate value of Summit stockholders’ shares and minimize the risks and uncertainty affecting the future prospects of Summit, including the potential execution risks associated with its stand-alone financial plan. Accordingly, the Summit board of directors unanimously (i) determined that it is in the best interests of Summit and its stockholders, and declared it advisable, that Summit enter into the merger agreement and consummate the transactions contemplated thereby,

(ii) approved and declared advisable the execution and delivery of the merger agreement and the consummation of the transactions contemplated thereby, including the merger, and (iii) directed that the merger agreement and the transactions contemplated thereby be submitted for consideration by Summit stockholders entitled to vote thereon at a meeting thereof.

In addition, the Summit board of directors was aware of and considered the interests that Summit’s directors and executive officers may have with respect to the merger that differ from, or are in addition to, the interests of Summit stockholders generally, as described below under “—Interests of Summit’s Directors and Executive Officers in the Merger.”

The foregoing discussion of the information and factors considered by the Summit board of directors is not exhaustive, but Summit believes it includes all the material factors considered by the Summit board of directors. In view of the wide variety of factors considered in connection with its evaluation of the merger and the complexity of these matters, the Summit board of directors did not consider it practicable to, and did not attempt to, quantify or otherwise assign relative or specific weight or values to any of these factors. Rather, the Summit board of directors viewed its position and recommendation as being based on an overall analysis and on the totality of the information presented to and factors considered by it. In addition, in considering the factors described above, individual directors may have given different weights to different factors. The Summit board of directors based its unanimous recommendation on the totality of the information presented.

This explanation of Summit’s reasons for the merger and other information presented in this section is forward-looking in nature and, therefore, should be read in light of the factors described under “Cautionary Statement Regarding Forward-Looking Statements.”

Summit engaged Morgan Stanley as its financial advisor in connection with the proposed merger. On November 24, 2024, Morgan Stanley rendered its oral opinion to the Summit board of directors (which was subsequently confirmed in writing by delivery of Morgan Stanley’s written opinion addressed to the Summit board of directors dated the same date) as to, as of November 24, 2024, and subject to the various assumptions made, procedures followed, matters considered, and qualifications and limitations on the review undertaken by Morgan Stanley as set forth in its written opinion, the fairness, from a financial point of view, to the holders of Summit common stock of the merger consideration to be received by such holders in the merger pursuant to the merger agreement.

The full text of Morgan Stanley’s written opinion, which describes, among other things, the assumptions made, procedures followed, matters considered and qualifications and limitations on the review undertaken, is attached as Annex C to this proxy statement. The description of Morgan Stanley’s opinion contained in this proxy statement is qualified in its entirety by reference to the full text of the opinion. Morgan Stanley’s opinion was directed to the Summit board of directors, in its capacity as such, and addressed only the fairness, from a financial point of view and as of the date of such opinion, to the holders of Summit common stock of the merger consideration to be received by such holders in the merger pursuant to the merger agreement. Morgan Stanley’s opinion did not address the relative merits of the transactions contemplated by the merger agreement as compared to other business or financial strategies that might be available to Summit, nor did it address the underlying business decision of Summit to enter into the merger agreement. Morgan Stanley’s opinion is not intended to be and does not constitute a recommendation as to how the Summit board of directors or any securityholder should vote or act on any matters relating to the proposed merger or otherwise.

In arriving at its opinion, Morgan Stanley, among other things:

Morgan Stanley assumed and relied upon, without independent verification, the accuracy and completeness of the information that was publicly available or supplied or otherwise made available to Morgan Stanley by Summit, and formed a substantial basis for Morgan Stanley’s opinion. With respect to the financial projections for Summit, Morgan Stanley assumed that they had been reasonably prepared on bases reflecting the best currently available estimates and judgments of the management of Summit as to the future financial performance of Summit and the other matters addressed thereby. At Summit’s direction, Morgan Stanley used and relied upon the financial projections for Summit for purposes of its analyses and opinion. Morgan Stanley expressed no view or opinion with respect to the financial projections for Summit, or the assumptions and methodologies upon which they are based.

In addition, Morgan Stanley assumed that the merger would be consummated in accordance with the terms set forth in the merger agreement without any waiver, amendment or delay of any terms or conditions, including, among other things, that Quikrete will obtain financing in accordance with the terms set forth in commitment letters furnished to Morgan Stanley and that the definitive merger agreement would not differ in any material respect from the draft thereof furnished to Morgan Stanley. Morgan Stanley assumed that in connection with the receipt of all the necessary governmental, regulatory or other approvals and consents required for the proposed merger, no delays, limitations, conditions or restrictions would be imposed that would have a material adverse effect on Summit or the contemplated benefits of the merger. Morgan Stanley is not a legal, tax or regulatory advisor. Morgan Stanley is a financial advisor only and Morgan Stanley relied upon, without independent verification, the assessment of Summit and its legal, tax, and regulatory advisors respect to such matters. Morgan Stanley expressed no opinion with respect to the fairness of the amount or nature of the compensation to any of the officers, directors or employees of the parties, or any class of such persons, to the transactions contemplated by the merger agreement relative to the merger consideration or otherwise. Morgan Stanley did not make any independent valuation or appraisal of the assets or liabilities of Summit, nor had Morgan Stanley been furnished with any such valuations or appraisal. Morgan Stanley’s opinion is necessarily based on financial, economic, market and other conditions as in effect on, and the information made available to Morgan Stanley as of, the date hereof. Events occurring or coming to Morgan Stanley’s attention after the date thereof may affect its opinion and the assumptions used in preparing it, and Morgan Stanley did not assume any obligation to update, revise or reaffirm its opinion.

Morgan Stanley’s opinion does not address the relative merits of the transactions contemplated by the merger agreement as compared to other business or financial strategies that might be available to Summit, nor does it address the underlying business decision of Summit to enter into the merger agreement. Morgan Stanley did not express any view on, and its opinion does not address, any other term or aspect of the merger agreement or the transactions contemplated thereby (including the treatment of Summit preferred stock or the obligations arising under the tax receivable agreement, dated March 11, 2015, among Summit and the other parties thereto, as a consequence of the merger or otherwise) or any term or aspect of any other agreement or instrument contemplated by the merger agreement or entered into or amended in connection therewith (including any voting agreement). In addition, representatives of Summit had advised Morgan Stanley, and Morgan Stanley assumed for purposes of its analyses and opinion, that no shares of Summit Class B common stock were issued and outstanding and no such shares would become issued and outstanding at any time prior to the closing of the merger.

The following is a summary of the material financial analyses performed by Morgan Stanley in connection with its oral opinion and the preparation of its written opinion to the Summit board of directors, both provided as of November 24, 2024. The following summary is not a complete description of the financial analyses performed and factors considered by Morgan Stanley in connection with its opinion, nor does the order of analyses described

represent the relative importance or weight given to those analyses. Except as otherwise noted, the following quantitative information, to the extent that it is based on market data, is based on market data as it existed on or before November 24, 2024. In arriving at its opinion, Morgan Stanley considered all of its analyses as a whole and did not attribute any particular weight to any single analysis described below. Considering any portion of such analyses and factors considered, without considering all analyses and factors, could create a misleading or incomplete view of the process underlying Morgan Stanley’s opinion. Some of these summaries of financial analyses include information presented in tabular format. In order to fully understand the financial analyses used by Morgan Stanley, the tables must be read together with the text of each summary. The tables alone do not constitute a complete description of the financial analyses. Furthermore, mathematical analysis is not in itself a meaningful method of using the data referred to below.

For purposes of its financial analysis and opinion, Morgan Stanley compared ranges of values indicated by its analyses with the per share merger consideration in the merger of $52.50. For its analyses, Morgan Stanley utilized and relied upon the number of issued and outstanding shares of Summit provided by the management of Summit.

Morgan Stanley performed a discounted cash flow (“DCF”) analysis for Summit, which is designed to provide an implied value of a company by calculating the present value of the estimated future cash flows and terminal value of a company. Morgan Stanley calculated a range of implied equity values per share of Summit common stock based on the estimated cash flows reflected in Summit’s financial projections.

For purposes of its DCF analysis, Morgan Stanley calculated a terminal value for Summit as of December 31, 2029, by applying a range of perpetuity growth rates of 2.0% to 3.0%, selected based on Morgan Stanley’s experience and professional judgment, to the terminal year unlevered free cash flow. The unlevered free cash flows from fiscal years 2025 to 2029 and the terminal value were then discounted to present values as of December 31, 2024 using a range of discount rates of 10.2% to 11.6% (which Morgan Stanley derived using its experience and professional judgment to reflect an estimated range of Summit’s assumed weighted average cost of capital), and adjusted by Summit’s estimated net debt as of December 31, 2024 of $2.035 billion, as provided by Summit’s management. Morgan Stanley divided the resulting equity value by the number of fully diluted shares of Summit common stock outstanding, as provided by Summit’s management.

Based on the above-described analysis, Morgan Stanley derived a range of implied equity values per share of Summit common stock of $39.25 per share to $56.00 per share, rounded to the nearest $0.25 per share, as compared to the merger consideration in the merger of $52.50.

Morgan Stanley performed a discounted equity value analysis, which is designed to provide insight into a theoretical estimate of the future implied value of a company’s common equity as a function of such company’s estimated future earnings and a theoretical range of trading multiples. The resulting estimated future implied value is subsequently discounted back to the present day at the company’s cost of equity in order to arrive at an illustrative estimate of the present value for the company’s theoretical future implied stock price.

As part of this analysis, Morgan Stanley calculated future ranges of implied equity values per share of Summit common stock as of each of December 31, 2025, December 31, 2026, December 31, 2027 and December 31, 2028, respectively, and subsequently discounted each such theoretical future value range to arrive at an illustrative present value range of implied share prices for Summit common stock as of November 22, 2024.

To calculate the future ranges of implied equity values, Morgan Stanley applied a range of multiples of 8.5x to 10.0x (selected by Morgan Stanley using its experience and professional judgment) to Summit’s estimated earnings before interest, taxes, depreciation and amortization (or EBITDA) for the next twelve months (or NTM) as of each of December 31, 2025, December 31, 2026, December 31, 2027 and December 31, 2028, in each case based on Summit’s financial projections, and then subtracted the amount of Summit’s estimated net debt as of each date, respectively, as provided by Summit’s management. Morgan Stanley then divided the resulting implied equity values by Summit’s fully diluted shares outstanding, as provided by Summit’s management, to derive ranges of future implied equity values per share. Morgan Stanley then discounted the resulting implied equity values per share to November 22, 2024 at a discount rate of 13.1% (which Morgan Stanley derived using its experience and professional judgment based on Summit’s assumed cost of equity).

Based on this analysis, Morgan Stanley derived a range of implied equity values per share of Summit common stock of $41.25 to $57.00, rounded to the nearest $0.25 per share, as compared to the merger consideration in the merger of $52.50.

Morgan Stanley performed a selected public companies analysis, which attempts to illustrate implied values of a company by comparing it to similar companies that are publicly traded. Morgan Stanley reviewed and compared, using publicly available financial information, certain estimates of future financial information for Summit with corresponding estimates of future financial information and public market multiples for publicly traded companies in the heavy building materials space that shared certain similar business and operating characteristics to Summit.

These companies were chosen based on Morgan Stanley’s experience and judgment regarding the industry and because they have businesses that may be considered similar in certain respects to Summit’s business. Although none of such companies is identical or directly comparable to Summit, these companies are publicly traded companies with operations and/or other criteria, that, for purposes of its analysis, Morgan Stanley considered similar to Summit.

For purposes of this analysis, for each of the selected publicly traded companies listed below, using publicly available information, including equity research analyst estimates, Morgan Stanley analyzed (i) the ratio as of November 22, 2024 of the aggregate value, or AV, which was defined as fully diluted market capitalization plus net debt, of such company to its estimated EBITDA for calendar year 2025 and (ii) the one-year average ratio over the twelve-month period ending November 22, 2024 (or One-Year Average) of the AV of such company to estimated NTM EBITDA.

Morgan Stanley calculated estimated implied equity values of Summit based on the AV/EBITDA multiples for each of the selected companies multiplied by Summit’s estimated EBITDA for fiscal year 2025, based on Summit’s financial projections, and adjusting implied AV’s for Summit by Summit’s estimated net debt as of September 30, 2024, as provided by Summit’s management. Morgan Stanley then divided the resulting implied equity values by Summit’s fully diluted shares outstanding, as provided by Summit’s management, to derive implied equity values per share of Summit common stock.

The applicable multiples for each of the selected companies and the corresponding estimated implied value per share of Summit common stock based on Summit’s financial projections (rounded to the nearest $0.25 per share) are summarized as follows:

No company utilized in the comparable company analysis is identical to Summit. In evaluating comparable companies, Morgan Stanley made judgments and assumptions with regard to industry performance, general business, economic, market and financial conditions, and other matters, many of which are beyond the control of Summit. These include, among other things, comparable company growth, the impact of competition on the businesses of Summit and the industry generally, industry growth and the absence of any adverse material change in the financial condition and prospects of Summit or the industry, or in the financial markets in general. Mathematical analysis is not in itself a meaningful method of using comparable company data.

Morgan Stanley performed a selected precedent transactions analysis, which is designed to imply a value of a company based on publicly available financial terms of selected transactions. Morgan Stanley selected certain transactions involving the acquisition of heavy building materials companies since 2015 for which relevant financial information was publicly available.

For these transactions, Morgan Stanley reviewed the consideration paid and calculated the ratio of the AV of each transaction to the EBITDA of the target company for the last twelve months prior to the transaction’s announcement, or LTM EBITDA, based on publicly available financial information. Morgan Stanley reviewed the following transactions in connection with this analysis:

These transactions varied significantly based upon company scale, product mix, and geography. Based on its experience and professional judgment and taking into consideration, among other things, the observed multiples for the selected transactions listed above (which indicated a median AV / LTM EBITDA multiple of 12.0x), Morgan Stanley selected a range of AV/LTM EBITDA multiples from 11.0x to 13.0x and applied this range of multiples to Summit’s estimated EBITDA for 2024, based on information provided by Summit, and adjusted the implied range of AV’s for Summit by Summit’s estimated net debt as of September 30, 2024, as provided by Summit’s management. Morgan Stanley then divided the resulting implied equity values by Summit’s fully diluted shares outstanding, as provided by Summit’s management, to derive implied equity values per share of Summit common stock. Based on the above-described analysis, Morgan Stanley derived a range of implied equity values per share of Summit common stock of $48.50 per share to $59.50 per share, rounded to the nearest $0.25 per share, as compared to the merger consideration in the merger of $52.50.

Morgan Stanley also observed certain additional information that was not considered part of its financial analyses with respect to its opinion but was noted for informational purposes, including the following:

Morgan Stanley reviewed the historical trading data of shares of the Summit Class A common stock for the 52-week period ending October 23, 2024 (the last trading day before published market rumors of a transaction) and noted that, during such period, the highest intraday trading price per share of the Summit Class A common stock was $44.89 and the lowest intraday trading price per share of the Summit Class A common stock was $30.83. Morgan Stanley further noted that the highest intraday trading price per share of the Summit Class A common stock during the 52-week period ending November 22, 2024 was $53.49.

Morgan Stanley reviewed (i) the premiums paid relative to the last closing share price for the applicable target prior to announcement (or market rumors) of the transaction and (ii) the premiums paid relative to the 52-week high closing share price for the applicable target prior to announcement (or market rumors) of the transaction, in each case for all transactions announced from January 1, 2000 to September 30, 2024 that involved U.S. public targets and had transaction values of $1 billion or more. Based on its review of such data, Morgan Stanley applied selected premiums of (i) 20% to 50% to Summit’s closing share price on October 23, 2024 (the last trading day before published market rumors of a transaction) and (ii) 0% to 20% to Summit’s 52-week high closing share price prior to October 23, 2024. This analysis indicated a range of implied equity values per share of Summit common stock of $48.75 per share to $61.00 per share (based on one-day premium) and $45.00 per share to $53.75 per share (based on 52-week high premium), each rounded to the nearest $0.25 per share, as compared to the merger consideration in the merger of $52.50.

Morgan Stanley reviewed sell-side equity research analyst price targets for shares of Summit common stock published by 16 equity research analysts. These targets generally reflect each analyst’s estimate of the 12-month future public market trading price per share of Summit common stock and were not discounted to reflect present values. The range of undiscounted price targets for shares of Summit common stock by these analysts (x) on or before October 23, 2024 (the last trading day before published market rumors of a transaction) was $41.00 per share to $56.00 per share and (y) after the published market rumors and Summit’s earnings report for the third quarter of 2024 through November 21, 2024 was $43.00 per share to $60.00 per share. The price targets published by equity research analysts do not necessarily reflect current market trading prices for shares of Summit common stock and these estimates are subject to uncertainties, including the future financial performance of Summit and future financial market conditions.

In preparing its opinion, Morgan Stanley performed a variety of financial and comparative analyses, including those described below. The summary of the analyses below is not a complete description of Morgan Stanley’s opinion or the analyses underlying, and factors considered in connection with, Morgan Stanley’s opinion. The preparation of

a financial opinion is a complex analytical process involving various determinations as to the most appropriate and relevant methods of financial analysis and the application of those methods to the particular circumstances and, therefore, a financial opinion is not readily susceptible to summary description. Morgan Stanley arrived at its ultimate opinion based on the results of all analyses and factors assessed as a whole, and it did not draw, in isolation, conclusions from or with regard to any one factor or method of analysis. Accordingly, Morgan Stanley believes that the analyses must be considered as a whole and in context and that selecting portions of its analyses and factors or focusing on information presented in tabular format, without considering all analyses and factors or the narrative description of the analyses, could create a misleading or incomplete view of the processes underlying such analyses and its opinion.

In its analyses, Morgan Stanley considered business, economic, industry and market conditions, financial and otherwise, and other matters as they existed on, and could be evaluated as of, the date of its opinion. No company, business or transaction used in Morgan Stanley’s analyses for comparative purposes is identical to Summit or the proposed merger. While the results of each analysis were taken into account in reaching its overall conclusion with respect to the fairness, from a financial point of view, of the merger consideration (to the extent expressly specified in Morgan Stanley’s opinion), Morgan Stanley did not make separate or quantifiable judgments regarding individual analyses. The reference ranges indicated by Morgan Stanley’s financial analyses are illustrative and not necessarily indicative of actual values nor predictive of future results or values, which may be significantly more or less favorable than those suggested by the analyses. In addition, any analyses relating to the value of assets, businesses or securities do not purport to be appraisals or to reflect the prices at which businesses or securities actually may be sold, which may depend on a variety of factors, many of which are beyond Summit’s control and the control of Morgan Stanley. Much of the information used in, and accordingly the results of, Morgan Stanley’s analyses are inherently subject to substantial uncertainty.

Morgan Stanley was selected by Summit to act as its financial advisor based on Morgan Stanley’s qualifications, experience and reputation. Morgan Stanley was not requested to, and it did not, recommend or determine the specific consideration payable in the merger or opine that any specific consideration constituted the only appropriate consideration for the merger. The type and amount of consideration payable in the merger were determined through negotiations between Summit and Quikrete and the decision of Summit to enter into the merger agreement was solely that of the Summit board of directors.

Morgan Stanley’s opinion to the Summit board of directors was one of many factors taken into consideration by the Summit board of directors in deciding to consider, approve and declare the advisability of the merger agreement and the transactions contemplated thereby and to recommend the approval of the merger by the holders of Summit common stock. Consequently, the analyses described above should not be viewed as determinative of the opinion of the Summit board of directors with respect to the merger consideration or of whether the Summit board of directors or management would have been willing to agree to a different merger consideration. The issuance of Morgan Stanley’s opinion was authorized by Morgan Stanley’s fairness opinion committee.

Morgan Stanley is a global financial services firm engaged in the securities, investment management and individual wealth management businesses. Morgan Stanley’s securities business is engaged in securities underwriting, trading and brokerage activities, foreign exchange, commodities and derivatives trading, prime brokerage, as well as providing investment banking, financing and financial advisory services. Morgan Stanley, its affiliates, directors or officers invest on a principal basis or manage funds that invest, hold long or short positions, finance positions, and trade or otherwise structure and effect transactions, for their own account or the accounts of its customers, in debt or equity securities or loans of Quikrete or Summit, or any other company, or any currency or commodity, that may be involved in this transaction, or any related derivative instrument.

In the two years prior to the date of its opinion, Morgan Stanley provided financial advisory and financing services for Summit and received fees of approximately $25 million to $50 million in connection with such services. In addition, Morgan Stanley or one or more of its affiliates is a lender to Summit. Morgan Stanley, in its November 6, 2024 relationship disclosure to Summit, noted that, as of November 4, 2024, it held an aggregate interest of less than 1% of the outstanding shares of Summit common stock. Morgan Stanley may also seek to provide financial advisory and financing services to Quikrete and Summit and their respective affiliates in the future and would expect to receive fees for the rendering of these services.

Morgan Stanley acted as financial advisor to the Summit board of directors in connection with the proposed merger and will receive a fee of approximately $83 million for such services, of which $7.5 million is payable in

connection with the delivery of the opinion and the remainder is payable upon the consummation of the merger. Summit agreed to reimburse Morgan Stanley for its expenses, including fees and expenses of counsel, incurred in connection with its engagement. In addition, Summit agreed to indemnify Morgan Stanley and related parties against certain liabilities, including liabilities under the federal securities laws, relating to or arising out of Morgan Stanley’s engagement.

Summit retained Evercore to act as its financial advisor in connection with the merger. As part of this engagement, Summit requested that Evercore evaluate the fairness, from a financial point of view, of the merger consideration to be received by the holders of Summit common stock (other than Quikrete or any subsidiary of Quikrete, Summit or any subsidiary of Summit, or holders of dissenting shares). At a meeting of the Summit board of directors held on November 24, 2024, Evercore rendered to the Summit board of directors its opinion to the effect that, as of November 24, 2024, and based upon and subject to the analyses, procedures, assumptions, limitations, qualifications and conditions described in Evercore’s opinion, the merger consideration of $52.50 in cash per share to be received by the holders of Summit common stock in the merger was fair, from a financial point of view, to such holders (other than Quikrete or any subsidiary of Quikrete, Summit or any subsidiary of Summit, or holders of dissenting shares).

The full text of the written opinion of Evercore, dated November 24, 2024, which sets forth, among other things, the procedures followed, assumptions made, matters considered and qualifications and limitations on the scope of review undertaken in rendering its opinion, is attached as Annex D to this proxy statement and is incorporated herein by reference. Summit encourages you to read this opinion carefully and in its entirety. Evercore’s opinion was addressed to, and provided for the information and benefit of, the Summit board of directors (in its capacity as such) in connection with its evaluation of the proposed merger. Evercore’s opinion did not, and the summary of its opinion and the related analyses set forth in this proxy statement do not, constitute a recommendation to the Summit board of directors or to any other persons in respect of the merger, including as to how any holder of shares of Summit common stock should vote or act in respect of the merger. Evercore’s opinion does not address the relative merits of the merger as compared to other business or financial strategies that might be available to Summit, nor does it address the underlying business decision of Summit to engage in the merger.

In connection with rendering its opinion, Evercore, among other things:

For purposes of Evercore’s analysis and opinion, Evercore assumed and relied upon the accuracy and completeness of the financial and other information publicly available, and all of the information supplied or otherwise made available to, discussed with, or reviewed by Evercore, without any independent verification of such information (and Evercore did not assume responsibility or liability for any independent verification of such information), and further relied upon the assurances of the management of Summit that they were not aware of any facts or circumstances that would make such information inaccurate or misleading. With respect to the forecasts,

Evercore assumed with Summit’s consent that they had been reasonably prepared on bases reflecting the best currently available estimates and good faith judgments of management of Summit as to the future financial performance of Summit and the other matters covered thereby. Evercore expressed no view as to the forecasts or the assumptions on which they were based.

For purposes of Evercore’s analysis and opinion, Evercore assumed, in all respects material to its analysis, that the representations and warranties of each party contained in the merger agreement were true and correct, that each party would perform all of the covenants and agreements required to be performed by it under the merger agreement and that all conditions to the consummation of the merger would be satisfied without waiver or modification thereof. Evercore further assumed, in all respects material to its analysis, that all governmental, regulatory or other consents, approvals or releases necessary for the consummation of the merger would be obtained without any delay, limitation, restriction or condition that would have an adverse effect on Summit or the consummation of the merger or reduce the contemplated benefits to the holders of Summit common stock of the merger.

Evercore did not conduct a physical inspection of the properties or facilities of Summit and did not make or assume any responsibility for making any independent valuation or appraisal of the assets or liabilities (including any contingent, derivative or other off-balance sheet assets and liabilities) of Summit, nor was Evercore furnished with any such valuations or appraisals, nor did Evercore evaluate the solvency or fair value of Summit under any state or federal laws relating to bankruptcy, insolvency or similar matters. Evercore’s opinion was necessarily based upon information made available to Evercore as of November 24, 2024 and financial, economic, market and other conditions as they existed and as could be evaluated on that date. It was understood that subsequent developments could affect Evercore’s opinion and Evercore does not have any obligation to update, revise or reaffirm its opinion.

Evercore was not asked to pass upon, and expressed no opinion with respect to, any matter other than the fairness to the holders of the Summit common stock (other than Quikrete or any subsidiary of Quikrete, Summit or any subsidiary of Summit, or holders of dissenting shares), from a financial point of view, of the merger consideration. Evercore did not express any view on, and Evercore’s opinion did not address, the fairness of the proposed transaction to, or any consideration received in connection therewith by, the holders of any other class of securities, creditors or other constituencies of Summit, nor as to the fairness of the amount or nature of any compensation to be paid or payable to any of the officers, directors or employees of Summit, or any class of such persons, whether relative to the merger consideration or otherwise. Evercore was not asked to, nor did Evercore express any view on, and Evercore’s opinion did not address, any other term or aspect of the merger agreement or the merger, including, without limitation, the structure or form of the merger, any offer to purchase, redeem or exchange, or consent solicitation undertaken with respect to, outstanding debt securities of Summit, or any term or aspect of any other agreement or instrument contemplated by the merger agreement or entered into or amended in connection with the merger agreement (including the voting agreement). Evercore’s opinion did not address the relative merits of the merger as compared to other business or financial strategies that might be available to Summit, nor did it address the underlying business decision of Summit to engage in the merger. Evercore’s opinion did not constitute a recommendation to the Summit board of directors or to any other persons in respect of the merger, including as to how any holder of shares of Summit common stock should vote or act in respect of the merger. Evercore did not express any opinion as to the prices at which shares of Summit common stock would trade at any time, as to the potential effects of volatility in the credit, financial and stock markets on Summit or the merger or as to the impact of the merger on the solvency or viability of Summit or the ability of Summit to pay its obligations when they come due. Evercore is not a legal, regulatory, accounting or tax expert and assumed the accuracy and completeness of assessments by Summit and its advisors with respect to legal, regulatory, accounting and tax matters.

Set forth below is a summary of the material financial analyses reviewed by Evercore with the Summit board of directors on November 24, 2024, in connection with rendering its opinion. The following summary, however, does not purport to be a complete description of the analyses performed by Evercore. The order of the analyses described and the results of these analyses do not represent relative importance or weight given to these analyses by Evercore. Except as otherwise noted, the following quantitative information, to the extent that it is based on market data, is based on market data that existed on or before November 24, 2024 and is not necessarily indicative of current market conditions.

For purposes of its analyses and reviews, Evercore considered general business, economic, market and financial conditions, industry sector performance, and other matters, as they existed and could be evaluated as of the date of its opinion, many of which are beyond the control of Summit. The estimates contained in Evercore’s analyses and reviews, and the ranges of valuations resulting from any particular analysis or review, are not necessarily indicative

of actual values or predictive of future results or values, which may be significantly more or less favorable than those suggested by Evercore’s analyses and reviews. In addition, analyses and reviews relating to the value of companies, businesses or securities do not purport to be appraisals or to reflect the prices at which companies, businesses or securities actually may be sold. Accordingly, the estimates used in, and the results derived from, Evercore’s analyses and reviews are inherently subject to substantial uncertainty.

The following summary of Evercore’s financial analyses includes information presented in tabular format. In order to fully understand the analyses, the tables should be read together with the full text of each summary. The tables are not intended to stand alone and alone do not constitute a complete description of Evercore’s financial analyses. Considering the tables below without considering the full narrative description of Evercore’s financial analyses, including the methodologies and assumptions underlying such analyses, could create a misleading or incomplete view of such analyses.

Evercore performed a discounted cash flow analysis of Summit to calculate the estimated present value of the standalone unlevered, after-tax free cash flows, defined as net operating profit after tax, plus depreciation and amortization, less changes in net working capital and capital expenditures, that Summit was forecasted to generate during the period from the fourth quarter of Summit’s fiscal year 2024 through fiscal year 2029 based on the forecasts provided to Evercore by Summit’s management (as described in more detail under “—Summit Management Financial Projections”). Evercore calculated terminal values for Summit by applying perpetuity growth rates of 4.0% to 5.0%, which range was selected based on Evercore’s professional judgment and experience, to terminal year estimates of the unlevered, after-tax free cash flows that Summit was forecasted to generate based on the forecasts. The cash flows and terminal values in each case were then discounted to present value as of September 30, 2024, using discount rates ranging from 10.50% to 11.75%, which were based on an estimate of Summit’s weighted average cost of capital, and the mid-year cash flow discounting convention. In calculating implied total enterprise values, Evercore included the present value of tax savings from Summit’s estimated usage of net operating losses based on the forecasts ranging from $126 million to $128 million. Based on this range of implied total enterprise values, Summit’s estimated net debt of $2,197 million (calculated as total debt plus debt-like liabilities less cash and cash equivalents) as of September 30, 2024, and the number of fully diluted outstanding shares of Summit common stock of 177.4 million, in each case as provided by Summit’s management, this analysis indicated a range of implied equity values per share of Summit common stock, rounded to the nearest $0.25, of $41.75 to $61.50, compared to the merger consideration of $52.50 in cash per share of Summit common stock.

Evercore reviewed and compared certain financial information of Summit to corresponding financial multiples and ratios for the following selected publicly traded companies in the building materials industry (referred to as the “selected companies”):

For each of the selected companies, Evercore calculated total enterprise value (defined as fully diluted equity market capitalization plus total debt plus debt-like liabilities plus minority interest plus preferred equity less cash and cash equivalents less investments in affiliates) as a multiple of estimated 2024 and 2025 earnings before interest, taxes, depreciation and amortization before stock-based compensation expense, transaction and integration expenses (referred to as “Adjusted EBITDA,” such estimated 2024 and 2025 earnings referred to as “2024E Adjusted EBITDA” and “2025E Adjusted EBITDA,” respectively, and such multiples referred to as “TEV / 2024E Adjusted EBITDA” and “TEV / 2025E Adjusted EBITDA,” respectively), based on closing share prices as of November 22, 2024. Estimated financial data of the selected companies were based on publicly available research analysts’ estimates.

This analysis indicated the following:

Based on the multiples it derived for the selected companies and based on its professional judgment and experience, Evercore applied TEV / Adjusted EBITDA multiple reference ranges of 10.0x to 13.0x to Summit’s 2024E Adjusted EBITDA and 9.0x to 12.0x to Summit’s 2025E Adjusted EBITDA based on the forecasts. Based on these ranges of implied total enterprise values, Summit’s estimated net debt of $2,197 million (calculated as total debt plus debt-like liabilities less cash and cash equivalents) as of September 30, 2024, and the number of fully diluted outstanding shares of Summit common stock of 177.4 million, in each case as provided by Summit’s management, this analysis indicated ranges of implied equity values per share of Summit common stock, rounded to the nearest $0.25, of $42.75 to $59.50 for 2024E and $41.25 to $59.00 for 2025E, in each case compared to the merger consideration of $52.50 in cash per share of Summit common stock.

Although none of the selected companies is directly comparable to Summit, Evercore selected these companies because they are publicly traded companies in the building materials industry that Evercore, in its professional judgment and experience, considered generally relevant to Summit for purposes of its financial analyses. In evaluating the selected companies, Evercore made judgments and assumptions with regard to general business, economic and market conditions affecting the selected companies and other matters, as well as differences in the selected companies’ financial, business and operating characteristics. Accordingly, an evaluation of the results of this analysis is not entirely mathematical. Rather, this analysis involves complex considerations and judgments regarding many factors that could affect the relative values of the selected companies and the multiples derived from the selected companies. Mathematical analysis, such as determining the median, is not in itself a meaningful method of using the data of the selected companies.

Evercore reviewed financial information related to the following selected transactions involving target companies in the building materials industry announced since 2014 (referred to as the “selected transactions”). The selected transactions reviewed by Evercore, and the month and year each was announced, were as follows:

For each selected transaction, Evercore calculated the implied total enterprise value (defined as the target company’s implied equity value based on the consideration paid in the applicable transaction plus total debt plus debt-like liabilities plus minority interest less cash and cash equivalents) as a multiple of last twelve-month Adjusted EBITDA for the target company at the time of the announcement of the applicable transaction (referred to as “LTM

Adjusted EBITDA” and such multiple referred to as “TEV / LTM Adjusted EBTIDA”). Estimated financial data of the selected transactions were based on publicly available information at the time of announcement of the relevant transaction.

This analysis indicated the following:

Based on the multiples it derived from the selected transactions and based on its professional judgment and experience, Evercore selected a reference range of TEV / LTM Adjusted EBITDA multiples of 11.0x to 13.0x and applied this range of multiples to Summit’s estimated LTM Adjusted EBITDA as of September 30, 2024, based on the financial results for Summit provided by Summit’s management. Based on this range of implied total enterprise values, Summit’s estimated net debt of $2,197 million (calculated as total debt plus debt-like liabilities less cash and cash equivalents) as of September 30, 2024, and the number of fully diluted outstanding shares of Summit common stock of 177.4 million, in each case as provided by Summit’s management, this analysis indicated a range of implied equity values per share of Summit common stock, rounded to the nearest $0.25, of $47.25 to $58.25, compared to the merger consideration of $52.50 in cash per share of Summit common stock.

Although none of the target companies or businesses reviewed in the selected transactions analysis is directly comparable to Summit and none of the selected transactions is directly comparable to the merger, Evercore selected these transactions because they involve companies or businesses that Evercore, in its professional judgment and experience, considered generally relevant to Summit for purposes of its financial analyses. In evaluating the selected transactions, Evercore made judgments and assumptions with regard to general business, economic and market conditions and other factors existing at the time of the selected transactions, and other matters, as well as differences in financial, business and operating characteristics and other factors relevant to the target companies or businesses in the selected transactions. Accordingly, an evaluation of the results of this analysis is not entirely mathematical. Rather, this analysis involves complex considerations and judgments regarding many factors that could affect the relative values of the target companies or businesses in the selected transactions and the multiples derived from the selected transactions. Mathematical analysis, such as determining the median, is not in itself a meaningful method of using the data of the selected transactions.

Evercore also noted certain other factors, which were not considered material to its financial analyses with respect to its opinion, but were referenced for informational purposes only, including, among other things, the following:

Evercore reviewed historical trading prices of shares of Summit common stock during the 52-week period ended October 23, 2024, the last trading day prior to the public disclosure of the receipt by Summit of a non-binding acquisition proposal, noting that the low and high closing prices during such period ranged from $31.28 to $44.57 per share of Summit common stock, respectively.

Evercore reviewed selected public market trading price targets for the shares of Summit common stock prepared and published by equity research analysts that were publicly available as of October 23, 2024, the last trading day prior to the public disclosure of the receipt by Summit of a non-binding acquisition proposal, and as of November 22, 2024. These price targets reflect analysts’ estimates of the future public market trading price of the shares of Summit common stock at the time the price target was published. As of October 23, 2024 and November 22, 2024, the ranges of selected equity research analyst price targets per share were $41.00 to $56.00 and $47.00 to $60.00, respectively. Public market trading price targets published by equity research analysts do not necessarily reflect current market trading prices for the shares of Summit common stock and these target prices and the analysts’ earnings estimates on which they were based are subject to risk and uncertainties, including factors affecting the financial performance of Summit and future general industry and market conditions.

Evercore reviewed 48 transactions and announced bids for control of U.S. public targets with an aggregate transaction value between $5 billion and $15 billion announced in the ten-year period ended November 22, 2024. Using publicly available information, Evercore calculated the premiums paid as the percentage by which the per share consideration paid or proposed to be paid in each such transaction exceeded the 30-day volume weighted average price (“VWAP”) per share of the target companies on the pre-leak date of each transaction.

This analysis indicated the following:

Based on the results of this analysis and its professional judgment and experience, Evercore applied a premium range of 25.0% to 45.0% to the pre-leak 30-day VWAP of Summit common stock of $39.26 as of October 23, 2024, the last trading day prior to the public disclosure of the receipt by Summit of a non-binding acquisition proposal. This analysis indicated a range of implied equity values per share of Summit common stock, rounded to the nearest $0.25, of $49.00 to $57.00, compared to the merger consideration of $52.50 in cash per share of Summit common stock.

The foregoing summary of Evercore’s financial analyses does not purport to be a complete description of the analyses or data presented by Evercore to the Summit board of directors. In connection with the review of the merger by the Summit board of directors, Evercore performed a variety of financial and comparative analyses for purposes of rendering its opinion. The preparation of a fairness opinion is a complex process and is not necessarily susceptible to partial analysis or summary description. Selecting portions of the analyses or of the summary described above, without considering the analyses as a whole, could create an incomplete view of the processes underlying Evercore’s opinion. In arriving at its fairness determination, Evercore considered the results of all the analyses and did not draw, in isolation, conclusions from or with regard to any one analysis or factor considered by it for purposes of its opinion. Rather, Evercore made its determination as to fairness on the basis of its professional judgment and experience after considering the results of all the analyses. In addition, Evercore may have given various analyses and factors more or less weight than other analyses and factors, and may have deemed various assumptions more or less probable than other assumptions. As a result, the ranges of valuations resulting from any particular analysis or combination of analyses described above should not be taken to be the view of Evercore with respect to the actual value of the shares of Summit common stock. Rounding may result in total sums set forth in this section not equaling the total of the figures shown.

Evercore prepared these analyses for the purpose of providing an opinion to the Summit board of directors as to the fairness, from a financial point of view, of the merger consideration to be received by the holders of Summit common stock (other than Quikrete or any subsidiary of Quikrete, Summit or any subsidiary of Summit, or holders of dissenting shares). These analyses do not purport to be appraisals or to necessarily reflect the prices at which the business or securities actually may be sold. Any estimates contained in these analyses are not necessarily indicative of actual future results, which may be significantly more or less favorable than those suggested by such estimates. Accordingly, estimates used in, and the results derived from, Evercore’s analyses are inherently subject to substantial uncertainty, and Evercore assumes no responsibility if future results are materially different from those forecasted in such estimates.

Evercore’s financial advisory services and its opinion were provided for the information and benefit of the Summit board of directors (in its capacity as such) in connection with its evaluation of the proposed merger. The issuance of Evercore’s opinion was approved by an Opinion Committee of Evercore.

Evercore did not recommend any specific amount of consideration to the Summit board of directors or Summit’s management or that any specific amount of consideration constituted the only appropriate consideration in the merger for the holders of Summit common stock.

Pursuant to the terms of Evercore’s engagement letter with Summit, Summit has agreed to pay Evercore a fee for its services in the amount of approximately $55 million, of which $7.5 million was paid upon delivery of

Evercore’s opinion, and the balance of which will be payable contingent upon the consummation of the merger. Summit has also agreed to reimburse Evercore for its expenses and to indemnify Evercore against certain liabilities arising out of its engagement.

During the two-year period prior to the date of its opinion, Evercore and its affiliates have not been engaged to provide financial advisory or other services to Summit and Evercore has not received any compensation from Summit during such period. In addition, during the two-year period prior to the date of its opinion, Evercore and its affiliates have not been engaged to provide financial advisory or other services to Quikrete or its known affiliates, Contech Holdings Inc., Custom Building Products LLC, Hydro Conduit LLC and Quality Block Company Inc. (collectively, “Quikrete Affiliates”), and Evercore has not received any compensation from Quikrete or the Quikrete Affiliates during such period. Evercore may provide financial advisory or other services to Summit, Quikrete and the Quikrete Affiliates in the future, and in connection with any such services Evercore may receive compensation.

Evercore and its affiliates engage in a wide range of activities for its and their own accounts and the accounts of customers, including corporate finance, mergers and acquisitions, equity sales, trading and research, private equity, placement agent, asset management and related activities. In connection with these businesses or otherwise, Evercore and its affiliates and/or its or their respective employees, as well as investment funds they manage or in which any of them has a financial interest, invest, trade or otherwise effect transactions for their own accounts or the accounts of customers, in debt or equity securities, senior loans and/or derivative products or other financial instruments of or relating to Summit, Quikrete, potential parties to the merger and/or any of their respective affiliates or persons that are competitors, customers or suppliers of Summit or Quikrete.

Summit engaged Evercore to act as a financial advisor based on Evercore’s qualifications, experience and reputation. Evercore is an internationally recognized investment banking firm and regularly provides fairness opinions to its clients in connection with mergers and acquisitions, leveraged buyouts and valuations for corporate and other purposes.

While Summit has from time to time provided limited financial guidance to investors, Summit’s management does not, as a matter of course, otherwise publicly disclose forecasts or internal projections as to future performance due to, among other things, the inherent difficulty of predicting financial performance for future periods and the likelihood that the underlying assumptions and estimates may not be realized. In connection with the merger, Summit provided certain unaudited non-public financial projections regarding Summit to the Summit board of directors (referred to as the “financial projections”). At the direction of the Summit board of directors, the financial projections were also provided to, and approved for use by, Morgan Stanley and Evercore for purposes of performing their respective financial analyses in connection with rendering their respective opinions to the Summit board of directors, subject to the assumptions and limitations described in their respective opinions (as more fully described above under “—Opinion of Summit’s Financial Advisor – Morgan Stanley” and “—Opinion of Summit’s Financial Advisor – Evercore”). A summary of the financial projections is included below to give Summit stockholders access to certain information that was considered by the Summit board of directors for purposes of evaluating the merger. These projections are not, and should not be viewed as, public guidance or even targets.

The financial projections, while presented with numerical specificity, were based on numerous variables and assumptions, including about future performance, that are inherently uncertain and many of which are beyond Summit’s control. The financial projections reflect numerous estimates, assumptions and judgments made by Summit management, based on information available at the time the financial projections were developed, with respect to industry performance and competition, general business, economic, regulatory, market and financial conditions, other future events and matters specific to Summit’s business, all of which are difficult to predict and many of which are beyond Summit’s control. There can be no assurances that the financial projections accurately reflect future trends or accurately estimate Summit’s future financial and operating performance. The financial projections also reflect assumptions as to certain business decisions that are subject to change. Important factors that may affect actual results and cause the financial projections not to be achieved include, but are not limited to, risks and uncertainties relating to Summit’s business (including the ability to achieve strategic goals, objectives and targets over the applicable periods), industry performance, general business and economic conditions and other factors described in or referenced under the section titled “Cautionary Statement Regarding Forward-Looking Statements” and those risks and uncertainties detailed in Summit’s public filings with the SEC. Further, the financial projections cover multiple years and by their nature become subject to greater uncertainty with each successive year. Accordingly, there can be

no assurance that the financial projections will be realized, and actual results may vary materially from those shown. Modeling and forecasting the future performance of a home building products company is a highly speculative endeavor. Since the financial projections cover a long period of time, the financial projections by their nature are unlikely to anticipate each circumstance that will have an effect on the commercial value of Summit’s products and services.

The financial projections were not prepared with a view toward public disclosure and, accordingly, do not necessarily comply with published guidelines of the SEC or the guidelines established by the American Institute of Certified Public Accountants for preparation or presentation of prospective financial information or generally accepted accounting principles in the United States (referred to as “GAAP”).

The financial projections included in this document, including the financial projections set forth below under “—Summit Management Financial Projections,” are the responsibility of Summit’s management. KPMG LLP (referred to as “KPMG”), Summit’s independent registered public accounting firm, has not audited, reviewed, examined, compiled nor applied agreed-upon procedures with respect to the financial projections and, accordingly, KPMG has not expressed an opinion or any other form of assurance with respect thereto. The KPMG report on Summit’s consolidated financial statements incorporated by reference from Summit’s Annual Report on Form 10-K for the fiscal year ended December 30, 2023, relates to Summit’s previously issued financial statements. It does not extend to the financial projections and should not be read to do so.

The financial projections are not being included in this proxy statement in order to influence any Summit stockholder’s decision as to whether or not to approve the merger or whether or not to seek appraisal rights with respect to shares of Summit common stock held by such stockholder. The summary of the financial projections is being included in this proxy statement solely because these financial projections were made available to the Summit board of directors, Morgan Stanley and Evercore.

The financial projections do not take into account any circumstances or events occurring after the date they were prepared, including the announcement of the merger and merger-related expenses. The financial projections also do not take into account the effect of any failure of the merger to close and should not be viewed as accurate or continuing in that context.

The inclusion of the financial projections in this proxy statement should not be regarded as an indication that Summit, Morgan Stanley, Evercore or any of their respective affiliates, advisors or representatives considered or consider the financial projections to be predictive of actual future events, and the financial projections should not be relied on as such. None of Summit, Morgan Stanley, Evercore or any of their respective affiliates, advisors, officers, directors or representatives can give any assurance that actual results will not differ from these financial projections, and none of them undertakes any obligation to update or otherwise revise or reconcile the financial projections to reflect circumstances existing after the date such financial projections were generated or to reflect the occurrence of future events even in the event that any or all of the assumptions underlying the financial projections are shown to be in error or no longer appropriate. Summit does not intend to make publicly available any update or other revisions to the financial projections, except as required by law. None of Summit, Morgan Stanley, Evercore or any of their respective affiliates, advisors, officers, directors or representatives has made or makes any representation to any stockholder or other investor regarding the ultimate performance of Summit compared to the information contained in the financial projections or that the projected results will be achieved.

Summit stockholders are cautioned not to place undue, if any, reliance on the financial projections included in this proxy statement.

The financial projections incorporate certain financial measures which are not GAAP measures. Such financial measures should not be considered in isolation from, or as a substitute for, financial information presented in accordance with GAAP. Summit’s calculations of these financial measures may differ from others in its industry and are not necessarily comparable with information presented under similar captions used by other companies. Financial measures provided to a financial advisor are excluded from the SEC’s definition of non-GAAP financial measures and therefore are not subject to SEC rules regarding disclosures of non-GAAP financial measures, which may otherwise require a reconciliation of a non-GAAP financial measure to a GAAP financial measure to be presented. Reconciliations of these financial measures were not relied upon by Morgan Stanley or Evercore for purposes of performing their respective financial analyses in connection with rendering their respective opinions to the Summit

board of directors (as described in the sections titled “—Opinion of Summit’s Financial Advisor – Morgan Stanley” and “—Opinion of Summit’s Financial Advisor – Evercore”) or by the Summit board of directors. Accordingly, a reconciliation of the financial measures included in the financial projections is not provided.

Subject to the foregoing qualifications, the financial projections are set forth below:

For additional information on Summit’s actual results and historical financial information, see the section titled “Where You Can Find More Information.”

Summit’s directors and executive officers have interests in the merger that may be different from, or in addition to, those of Summit stockholders generally. These interests include, among others, vesting of equity awards and potential severance payments and benefits. The Summit board of directors was aware of and considered these interests, among other matters, in evaluating and negotiating the merger agreement and the merger, in approving the merger agreement, and in recommending the approval of the merger agreement by the Summit stockholders. Summit’s stockholders should take these interests into account in deciding whether to vote “FOR” the merger agreement proposal. These interests are described below, and certain of them are quantified within the narrative disclosure. The merger will constitute a “change in control” for purposes of the compensation arrangements described below. The amounts presented in the following discussion do not reflect the impact of applicable withholding or other taxes.

Effective as of immediately prior to the effective time, each Summit RSU that is outstanding immediately prior to the effective time will fully vest and be canceled and converted into the right to receive an amount in cash equal to the product of (i) the merger consideration, multiplied by (ii) the number of shares of Summit common stock subject to such vested award of Summit RSUs. Notwithstanding the foregoing, any Summit RSUs that are granted in 2025 or later and that are outstanding immediately prior to the effective time will vest on a pro rata basis (rather than in full) as of immediately prior to the effective time, unless the award holder’s employment is being terminated without cause or due to a constructive termination upon the effective time, in which case such award holder’s Summit RSUs that are granted in 2025 or later will vest in full.

Effective as of immediately prior to the effective time, each Summit PSU that is outstanding immediately prior to the effective time will vest, based on performance at target, and be canceled and converted into the right to receive an amount in cash equal to (i) the merger consideration, multiplied by (ii) the number of shares of Summit common stock subject to such vested award of Summit PSUs.

Effective as of immediately prior to the effective time, each Summit option that is outstanding immediately prior to the effective time will fully vest, to the extent not vested previously, and be canceled and converted into the right to receive an amount in cash equal to (i) the excess, if any, of the merger consideration over the applicable exercise price per share of Summit common stock subject to such award of Summit options, multiplied by (ii) the number of

shares of Summit common stock subject to such vested award of Summit options; provided that if the applicable exercise price per share of Summit common stock of an award of Summit options is equal to or greater than the merger consideration, such award of Summit options will be canceled at the effective time for no consideration.

See the section entitled “—Quantification of Potential Payments and Benefits to Summit’s Named Executive Officers in Connection with the Merger” for the estimated value of unvested Summit equity awards held by Summit’s named executive officers. Based on a per share price of Summit common stock of $52.50, the estimated aggregate amount that would be realized by the ten non-employee directors and the five Summit executive officers who are not named executive officers in respect of their unvested Summit equity awards that will vest upon completion of the merger is as follows: unvested Summit RSU awards held by non-employee directors—$3,054,025; unvested Summit RSU awards held by executive officers who are not named executive officers—$7,632,515; and unvested Summit PSU awards held by executive officers who are not named executive officers—$3,904,425. We note that these amounts include equity awards for Jason Kilgore (Executive Vice President & President Construction Materials, West Segment). In connection with Mr. Kilgore’s planned departure in spring 2025, Mr. Kilgore has entered into a transition and separation agreement (the “Kilgore transition agreement”) pursuant to which he will remain eligible to receive the equity award treatment under the merger agreement as though his employment continued through the effective time, provided that the effective time occurs on or prior to March 31, 2026. We also note that these amounts do not reflect outstanding Summit PSUs for the 2022-2024 performance cycle, which are currently anticipated to vest in the ordinary course based on actual performance prior to the effective time. On December 16, 2024, the Human Capital and Compensation Committee of the Summit board of directors (the “Compensation Committee”) (and, with respect to Summit’s Chief Executive Officer, the Summit board of directors) approved the granting of 2025 annual equity awards in the form of Summit RSUs, effective as of January 15, 2025, to each of Summit’s executive officers and non-employee directors. The aggregate amounts set forth above include the full value of Summit RSUs that will be granted in January 2025 (as we have assumed solely for purposes of this disclosure that each executive officer will be terminated without cause or experience a constructive termination immediately following the effective time).

The Summit 2021 Employee Stock Purchase Plan (the “Summit ESPP”) will be frozen and suspended at the end of the offering period that is in progress as of the date of the merger agreement and no new offering periods will commence under the Summit ESPP at any time on or after the date of the merger agreement. No current participant in the Summit ESPP will increase their payroll deduction elections or rate of contributions following the date of the merger agreement. The purchase date of any offering period that would be in effect at the effective time will be accelerated to a date on or prior to the fifth business day prior to the effective time. Each purchase right under any offering period that is in progress as of the date of the merger agreement will be fully exercised on the earlier of (i) the scheduled purchase date for such offering period and (ii) such accelerated exercise date, if applicable. Any participant payroll deductions not applied to the purchase of shares under the Summit ESPP after the final offering period will be returned to the participant without interest prior to the effective time. The Summit ESPP will terminate prior to the effective time. Nine of Summit’s executive officers (including Mses. Noonan and Anderson and Messrs. Anderson and Gaskill) are participants in the Summit ESPP.

Each of Summit’s executive officers is eligible for severance under Summit’s Executive Severance Plan (“Summit severance plan”), which provides for enhanced severance benefits in connection with a change in control. The Summit severance plan provides that, upon a termination of the executive officer’s employment by Summit without “cause” (and other than due to death or disability) or by the executive officer as a result of “constructive termination” (as such terms are defined in the Summit severance plan) during the two-year period beginning on the date of a change in control (for purposes of this section, a “qualifying change in control termination”), and subject to the executive officer’s execution and delivery of a release of claims and the executive officer’s compliance with non-competition, non-disparagement, non-solicitation and confidentiality covenants applicable pursuant to such executive officer’s participation notice and agreement under the Summit severance plan, the executive officer will be entitled to the following payments and benefits:

The estimated aggregate value of severance payments and benefits provided to Summit’s executive officers (other than named executive officers) under the Summit severance plan assuming that (a) the merger closed on February 28, 2025 (which, as an illustration, is the assumed closing date of the merger solely for purposes of estimating the aggregate value of severance payments and benefits that may be provided), (b) each such executive officer experiences a qualifying change in control termination immediately following consummation of the merger, and (c) each such executive officer has complied with all requirements necessary in order to receive all payments and benefits, is approximately $8,756,971. This amount includes severance that would be payable to Mr. Kilgore. Pursuant to the Kilgore transition agreement, Mr. Kilgore will remain eligible to receive severance under the Summit severance plan as though he experienced a qualifying change in control termination immediately following the effective time, provided that the effective time occurs on or prior to March 31, 2026.

In connection with the merger, and to mitigate the potential impact of Sections 280G and 4999 of the Internal Revenue Code (the “Code”) on Summit and certain executive officers, on December 16, 2024, with the advice of Aon’s Human Capital Solutions Practice, a division of Aon plc (“Aon”), Summit’s independent compensation consultant, the Compensation Committee (and, with respect to Summit’s Chief Executive Officer, the Summit board of directors) approved the following actions:

If an executive officer’s employment terminates prior to the date that the accelerated Summit RSUs would have normally vested (other than due to a termination without cause or a constructive termination), the executive officer will be required to repay the fair market value of the shares received in respect of the accelerated Summit RSUs on an after-tax basis.

These actions were intended to mitigate the potential impacts of Sections 280G and 4999 of the Code on Summit and the executive officers, including to preserve potential compensation-related corporate income tax deductions for Summit that might otherwise be disallowed through the operation of Section 280G of the Code and to mitigate or eliminate the amount of excise tax that may be payable by an executive officer pursuant to Section 4999 of the Code.

The information set forth below is required by Item 402(t) of Regulation S-K regarding compensation that is based on or otherwise relates to the merger that Summit’s named executive officers could receive in connection with the merger. Such amounts have been calculated assuming that:

The payments and benefits described below do not attempt to forecast any additional equity award grants, issuances or forfeitures that may occur after the date of this proxy statement but before the effective time. In addition, certain equity awards held by the named executive officers may vest in the ordinary course in accordance with their terms prior to the merger. As a result of the foregoing assumptions, which may or may not actually occur or be accurate on the relevant date, including the assumptions described in the footnotes to the table below, the actual amounts, if any, to be received by Summit’s named executive officers may differ materially from the amounts set forth below. Brian J. Harris (Former Executive Vice President and Chief Financial Officer) is not receiving any payments or benefits in connection with the merger.

Quikrete intends to fund the cash portion of the merger consideration with proceeds from new debt financing together with cash on hand. Concurrently with the entry into the merger agreement, Quikrete entered into the debt commitment letter, pursuant to which the lenders have committed to provide to Quikrete term debt financing in an aggregate principal amount of $9,200,000,000 (including up to $6,700,000,000 in bridge financing) together with a committed asset based revolving credit facility in an aggregate principal amount of up to $1,500,000,000 (subject to customary borrowing base limitations) (the foregoing referred to as the “debt financing”). The obligations of the lenders to provide debt financing under the debt commitment letter are subject to certain customary conditions, including (a) the execution and delivery of definitive documentation with respect to such financing in accordance with the debt commitment letter and (b) the consummation of the merger in all material respects in accordance with the terms and conditions of the merger agreement. The receipt of financing by Quikrete is not a condition to Quikrete’s obligations to complete the merger. Commitments in respect of the debt commitment letter will terminate on the earliest to occur of (1) the termination of the merger agreement in accordance with its terms prior to the consummation of the merger, (2) the consummation of the merger with or without the funding of the debt financing and (3) 5:00 p.m. Eastern time on August 24, 2025 (or as extended pursuant to the merger agreement). The proceeds of the debt financing would be used at the closing of the merger for the purposes of (1) financing the consummation of the merger, including paying fees and expenses incurred in connection with the merger, and (2) the repayment of all of Summit’s outstanding indebtedness under the Summit credit agreement and the Summit Indentures (each as defined below).

The merger is subject to the requirements of the HSR Act, which prevents Summit and Quikrete from completing the merger until each of Summit and Quikrete files a Notification and Report Form with the Antitrust Division of the DOJ and the FTC and the HSR Act waiting period is terminated or expires and no judgement, injunction, order or decree of a governmental authority shall have been entered and continue to be in effect. A transaction notifiable under the HSR Act may not be completed until the expiration of a 30-calendar-day waiting period following the parties’ filings of their respective HSR Act notification forms or the early termination of that waiting period. Quikrete may also choose to voluntarily re-start the initial 30-calendar-day waiting period by pulling and re-filing its Notification and Report Form prior to the expiration of the initial waiting period to give the agencies additional time to review the transaction. Before the expiration of the initial waiting period (or the re-started initial waiting period), the Antitrust Division of the DOJ or the FTC may issue a Second Request. If a Second Request is issued, the parties may not complete the merger until they have observed an additional 30-day waiting period, which would begin to run only after both parties have substantially complied with the Second Request, unless the waiting period is terminated earlier, or the parties commit not to close for some additional period of time. Summit and Quikrete submitted the requisite Notification and Report forms under the HSR Act on December 6, 2024, and the initial waiting period will expire on January 6, 2025 at 11:59 p.m. Eastern Time, unless it is extended by Quikrete pulling and refiling the initial Notification and Report Form, a Second Request for additional information is issued, it is terminated earlier, or if Summit and Quikrete commit not to close for some additional period of time.

In addition, the closing of the merger is subject to the requirements of the Competition Act (Canada), which prevent transactions such as the merger from being completed until (i) certain information and materials are furnished to the Canadian Commissioner of Competition appointed under the Competition Act (Canada), and (ii) the applicable waiting period is terminated or expires (provided that the Canadian Competition Tribunal has not issued an order temporarily or permanently prohibiting closing), unless the requirement to submit the required information and materials is waived by the Canadian Commissioner of Competition. The parties submitted the required information to the Canadian Commissioner of Competition on December 9, 2024.

The merger is also subject to the prior approval of the United States Nuclear Regulatory Commission, the Alabama Department of Public Health, the South Carolina Department of Health and Environmental Control and the Iowa Department of Health and Human Services with respect to certain radioactive materials licenses held indirectly by Summit.

For more information about regulatory approvals relating to the merger, see the section titled “The Merger Agreement—Conditions to the Merger.”

Although the parties expect that all required regulatory clearances will be obtained, the parties cannot assure you that these regulatory clearances will be timely obtained or obtained at all or that the granting of these regulatory clearances will not involve the imposition of additional conditions on the completion of the merger, including the requirement to divest assets, create or modify contractual rights or obligations or enter into supply or services agreements. These conditions could result in the conditions to the merger not being satisfied.

Summit stockholders who do not vote in favor of approval of the merger agreement proposal, who continuously hold their shares of Summit common stock and who otherwise comply precisely with the applicable provisions of Section 262 of the DGCL will be entitled to seek appraisal of the fair value of their shares of Summit common stock, as determined by the Delaware Court of Chancery, if the merger is completed, in lieu of receiving the merger consideration in respect of such shares. The “fair value” of your shares of Summit common stock as determined by the Delaware Court of Chancery could be greater than, the same as, or less than the value of the merger consideration that you would otherwise be entitled to receive under the terms of the merger agreement. Summit stockholders who wish to exercise the right to seek an appraisal of their shares must so advise Summit by submitting a written demand for appraisal in the form described in this proxy statement prior to the vote to approve the merger agreement proposal, and must otherwise follow the procedures prescribed by Section 262 of the DGCL.

The text of Section 262 of the DGCL is attached as Annex E to this proxy statement. You are encouraged to read these provisions carefully and in their entirety. Due to the complexity of the procedures for exercising appraisal rights, Summit stockholders who are considering exercising such rights are encouraged to seek the advice of legal counsel and their financial advisors. Failure to strictly comply with these provisions may result in the loss of appraisal rights.

The following describes the material provisions of the merger agreement, which is attached as Annex A to this proxy statement and is incorporated by reference herein. The summary of the material provisions of the merger agreement below and elsewhere in this proxy statement is qualified in its entirety by reference to the merger agreement. This summary does not purport to be complete and may not contain all of the information about the merger agreement that is important to you. Summit encourages you to read carefully the merger agreement in its entirety before making any decisions regarding the merger as it is the legal document governing the merger.

The merger agreement and this summary of its terms have been included to provide you with information regarding the terms of the merger agreement. Summit is responsible for considering whether additional disclosure of material information is required to make the statements in this proxy statement not misleading. Factual disclosures about Summit contained in this proxy statement or Summit’s public reports filed with the SEC may supplement, update or modify the factual disclosures about Summit contained in the merger agreement and described in this summary. The representations, warranties and covenants made in the merger agreement by Quikrete, Merger Sub and Summit are qualified and subject to important limitations agreed to by the parties to the merger agreement in connection with negotiating the terms of the merger agreement. In particular, in your review of the representations and warranties contained in the merger agreement and described in this summary, it is important to bear in mind that the representations and warranties were made solely for the benefit of the parties to the merger agreement, and were negotiated with the principal purpose of allocating risk between the parties to the merger agreement, rather than establishing matters as facts. The representations and warranties may also be subject to a contractual standard of materiality that may be different from that generally relevant to stockholders or applicable to reports and documents filed with the SEC, and in some cases are qualified by confidential disclosures that were made by each party to the other, which disclosures are not publicly disclosed. The representations and warranties in the merger agreement will not survive the completion of the merger.

Summit stockholders should not rely on representations, warranties and covenants or any descriptions thereof as characterizations of the actual state of facts or condition of Quikrete, Merger Sub, Summit or any of their respective subsidiaries or affiliates. Moreover, information concerning the subject matter of the representations and warranties may have changed since the date of the merger agreement. For the foregoing reasons, the representations, warranties and covenants or any descriptions of those provisions should not be read alone, but instead should be read together with the information provided elsewhere in this proxy statement and in the documents incorporated by reference into this proxy statement. See the section titled “Where You Can Find More Information.”

The merger agreement provides, upon the terms and subject to the conditions set forth therein and in accordance with Delaware law, for Merger Sub to merge with and into Summit, with Summit continuing as the surviving corporation and a wholly owned subsidiary of Quikrete.

Unless another place and time is mutually agreed to in writing by Quikrete and Summit, the closing of the merger will occur (a) no later than three business days after the satisfaction or waiver of the last to be satisfied or waived of the conditions set forth in the merger agreement (other than those conditions that by their terms are to be satisfied at the closing of the merger, but subject to the satisfaction or waiver (to the extent permitted by the merger agreement or applicable law) of such conditions). However, notwithstanding the foregoing, in no event shall Quikrete be obligated to consummate the closing of the merger prior to the third business day after the last day of the marketing period.

At the effective time, each share of Summit common stock issued and outstanding immediately prior to the effective time (other than (a) excluded shares and (b) dissenting shares), will be converted into the right to receive the merger consideration of $52.50 in cash, without interest and subject to deduction for any required withholding. At the effective time, all such shares will no longer be outstanding and will automatically be cancelled and retired and will cease to exist, and will thereafter represent only the right to receive $52.50 in cash, without interest.

At the effective time, each share of Summit common stock issued and outstanding immediately prior to the effective time that is held in treasury by Summit or owned, directly or indirectly, by Quikrete, Merger Sub or any other subsidiary of Quikrete will automatically be canceled and will cease to exist, and no consideration will be delivered in exchange for such shares.

Each share of Summit common stock held by any subsidiary of Summit immediately prior to the effective time will be converted into such number of common shares of the surviving corporation such that each subsidiary owns the same percentage of the capital stock in the surviving corporation immediately following the effective time as such subsidiary owned in Summit immediately prior to the effective time.

Each common share of Merger Sub outstanding immediately prior to the effective time will be converted into and become one common share of the surviving corporation and, except as described above under “—Shares Held by Summit Subsidiaries,” will constitute the only outstanding shares of capital stock of the surviving corporation.

Each share of Summit preferred stock outstanding immediately prior to the effective time will automatically be canceled and retired for no consideration and will cease to exist.

At the effective time, each Summit warrant issued and outstanding immediately prior to the effective time will be converted into the right to receive the merger consideration in an amount in cash, without interest and subject to deduction for any required withholding, equal to the product of (i) the number of Summit Class A common stock the holder of such Summit warrant would have received had such Summit warrant been exercised in full on a cash basis immediately prior to the effective time, multiplied by (ii) the excess, if any, of the merger consideration over the exercise price per Summit Class A common stock underlying such Summit warrant; provided, that if the exercise price per Summit Class A common stock underlying such Summit warrant is equal to or greater than the merger consideration, no payment shall be due to the holder of such Summit warrant. At the effective time, all such Summit warrants will no longer be outstanding and will automatically be cancelled and retired and will cease to exist, and will thereafter represent only the right to receive merger consideration in cash, without interest and subject to any required withholding.

Effective as of immediately prior to the effective time, each Summit RSU that is outstanding immediately prior to the effective time will fully vest and be canceled and converted into the right to receive an amount in cash equal to the product of (i) the merger consideration, multiplied by (ii) the number of shares of Summit common stock subject to such vested award of Summit RSUs. Notwithstanding the foregoing, any Summit RSUs that are granted in 2025 or later and that are outstanding immediately prior to the effective time will vest on a pro rata basis (rather than in full) as of immediately prior to the effective time, unless the award holder’s employment is being terminated without cause or due to a constructive termination upon the effective time, in which case such award holder’s Summit RSUs that are granted in 2025 or later will vest in full.

Effective as of immediately prior to the effective time, each Summit PSU that is outstanding immediately prior to the effective time will vest, based on performance at target, and be canceled and converted into the right to receive an amount in cash equal to (i) the merger consideration, multiplied by (ii) the number of shares of Summit common stock subject to such vested award of Summit PSUs.

Effective as of immediately prior to the effective time, each Summit option that is outstanding immediately prior to the effective time will fully vest, to the extent not vested previously, and be canceled and converted into the right to receive an amount in cash equal to (i) the excess, if any, of the merger consideration over the applicable exercise price per share of Summit common stock subject to such vested award of Summit options, multiplied by (ii) the

number of shares of Summit common stock subject to such award of Summit options; provided that if the applicable exercise price per share of Summit common stock of an award of Summit options is equal to or greater than the merger consideration, such award of Summit options will be canceled at the effective time for no consideration.

Shares of Summit common stock issued and outstanding immediately prior to the effective time and held by a Summit stockholder who is entitled to demand and who (i) did not vote in favor of the merger agreement proposal or consent in writing thereto and (ii) validly demanded their statutory rights of appraisal in respect of such shares of Summit common stock in accordance with Section 262 of the DGCL, will not be converted into, or represent the right to receive, the merger consideration unless such holder fails to perfect, withdraws or otherwise loses the right to appraisal. Instead, such dissenting stockholders will be entitled to receive payment of the appraised value of such shares of Summit common stock in accordance with Section 262 of the DGCL.

If any dissenting stockholder fails to perfect or otherwise effectively withdraws or loses their rights of appraisal, such shares of Summit common stock will thereupon be deemed to have been converted into, and to have become exchangeable for, as of the effective time, the right to receive the merger consideration. For more information regarding appraisal rights, see the section titled “Appraisal Rights of Summit Stockholders.” In addition, a copy of Section 262 of the DGCL is attached as Annex E to this proxy statement.

At the effective time of the merger, the certificate of incorporation of the surviving corporation, as in effect immediately prior to the completion of the merger, will be amended and restated in its entirety as set forth in Exhibit B to the merger agreement and, as so amended and restated, will be the certificate of incorporation of the surviving corporation.

The bylaws of Merger Sub, as in effect at the effective time of the merger, will be the bylaws of the surviving corporation. As used herein, the “effective time” of the merger means the time at which the certificate of merger with respect to the merger is duly filed with the Secretary of State of the State of Delaware or at such later time as Quikrete, Summit and Merger Sub may agree and specify in such certificate of merger.

From and after the effective time, until their successors are duly elected or appointed and qualified in accordance with applicable law, (a) the directors of Merger Sub at the effective time will be the directors of the surviving corporation and (b) the officers of Summit at the effective time will be the officers of the surviving corporation. Prior to the closing date of the merger, Summit will either remove (or cause the removal of) or use reasonable best efforts to procure resignation letters (in a form and substance reasonably satisfactory to Quikrete) of each individual serving as a director of any subsidiary of Summit or member of any committee of a subsidiary of the Summit board of directors, in each case, solely in such individual’s capacity as a director of any subsidiary of Summit and member of any such committee, and in each case conditioned upon and effective as of the closing of the merger, and will deliver, or cause to be delivered, to Quikrete such procured resignation letters (or evidence of such removal) at or prior to the closing of the merger.

As promptly as practicable after the effective time (but no later than two business days thereafter), Quikrete will send, or will cause the paying agent to send, to each Summit stockholder at the effective time a letter of transmittal and instructions, which will contain instructions on how to surrender certificated and book-entry shares of Summit common stock in exchange for the merger consideration. No interest will be paid or will accrue on the merger consideration payable upon surrender of any such shares of Summit common stock.

If any portion of the merger consideration is to be paid to a person other than the person in whose name the surrendered certificated or the transferred uncertificated shares of Summit stock is registered, it will be a condition to such payment that (a) either such certificate be properly endorsed or otherwise be in proper form for transfer or such uncertificated share be properly transferred and (b) the person requesting such payment will pay to the paying agent any transfer or other taxes required as a result of such payment or establish to the satisfaction of the paying agent that such tax has been paid or is not payable.

In the event that a Summit share certificate is lost, stolen or destroyed, the previous holder of the Summit share certificate may obtain the merger consideration by (a) making an affidavit regarding the loss, theft or destruction of

the Summit share certificate and (b) if required by the surviving corporation, agreeing to indemnify the surviving corporation against any claim that may be made with respect to such lost, stolen or destroyed certificate (including, if required by the surviving corporation, the posting by such person of a bond, in such reasonable amount as the surviving corporation may direct).

From and after the effective time, all holders of Summit share certificates and uncertificated shares will cease to have any rights as Summit stockholders other than the right to receive the merger consideration upon the surrender of such shares, without interest. From and after the effective time, the stock transfer books of Summit will be closed with respect to all shares of Summit common stock outstanding immediately prior to the effective time and there will be no further registration of transfers of Summit common stock.

None of the parties to the merger agreement or the paying agent will be liable to any person with respect to any portion of the merger consideration delivered to a governmental authority if required by any applicable abandoned property, escheat or similar law.

Any portion of the merger consideration made available to the paying agent (and any interest or other income earned thereon) that remains unclaimed by the holders of Summit common stock 12 months after the effective time will be returned to Quikrete, and such Summit stockholders must thereafter look only to Quikrete for payment of the merger consideration. Further, any portion of the merger consideration that remains undistributed to holders of Summit share certificates and uncertificated shares immediately prior to the date on which the merger consideration would otherwise escheat to or become the property of any governmental entity will, to the extent permitted by applicable law, become the property of Quikrete, free and clear of all claims or interest of any person previously entitled to such claims or interest.

Quikrete, Summit, the surviving corporation, the paying agent and any of their respective affiliates or agents will be entitled to deduct and withhold from any amounts otherwise payable pursuant to the merger agreement such amounts as are required to be deducted or withheld under the Code or any other applicable law in respect of taxes. Any amounts so deducted or withheld will, to the extent paid over to the appropriate taxing authority, be treated for all purposes of the merger agreement as having been paid to the person in respect of which such deduction or withholding was made.

The merger agreement contains customary representations and warranties of the parties. These include representations and warranties of Summit with respect to:

The merger agreement also contains customary representations and warranties of Quikrete and Merger Sub, including among other things:

The representations and warranties in the merger agreement do not survive the closing or termination of the merger agreement.

Certain of the representations and warranties made by the parties are qualified as to “knowledge,” “materiality” or “material adverse effect,” as defined in the merger agreement and described below.

A “material adverse effect” with respect to Summit means any change, effect, development, circumstance, condition, fact, state of facts, event or occurrence that, individually or in the aggregate, has had or would reasonably be expected to have a material adverse effect on the financial condition, assets, business, properties or results of

operations of Summit and its subsidiaries, taken as a whole, excluding any change, effect, development, circumstance, condition, fact, state of facts, event or occurrence to the extent resulting from:

A “material adverse effect” with respect to Quikrete means any change, effect, development, circumstance, condition, fact, state of facts, event or occurrence that would reasonably be expected to prevent, impair or materially delay the ability of Quikrete, Merger Sub or Summit to perform its material obligations under the merger agreement or prevent, impair or materially delay the consummation of the merger or the other transactions contemplated by the merger agreement as promptly as reasonably practicable and, in any event, on or prior to the outside date.

The merger agreement provides for certain restrictions on Summit’s and its subsidiaries’ activities until the earlier of the effective time or the date (if any) the merger agreement is terminated. In general, except as required

or expressly contemplated or permitted by the merger agreement, as required by applicable law or as consented to in writing by Quikrete (which may not be unreasonably withheld, conditioned or delayed), subject to specified exceptions set forth in the merger agreement and the confidential schedules thereto, Summit is required to (and to cause each of its subsidiaries to) use reasonable best efforts to (a) conduct its business in accordance with applicable law and in the ordinary course of business and (b) preserve intact in all material respects its current business operations, organization, ongoing businesses, license, permits and material business relationships with third parties, including vendors, suppliers, customers, partners and governmental authorities and maintain in full force and effect its insurance policies (including, for the avoidance of doubt, paying all premiums thereon and renewing or replacing such insurance policies on or prior to their expiration), in each case, consistent with past practice or customs in the industries in which Summit and its subsidiaries conduct business.

In addition, except as required or expressly contemplated or permitted by the merger agreement, as required by applicable law or as consented to in writing by Quikrete (which may not be unreasonably withheld, conditioned or delayed), subject to specified exceptions set forth in the merger agreement and the confidential schedules thereto, Summit must not and must not permit any of its subsidiaries to:

The merger agreement also provides for certain restrictions on Quikrete’s activities until the earlier of the effective time or the date the merger agreement is terminated. In general, Quikrete must not and must cause its subsidiaries not to take any action or fail to take any action that is intended to, or would reasonably be expected to, individually or in the aggregate, prevent, materially delay or materially impede the ability of Quikrete and Merger Sub to consummate the merger or the other transactions contemplated by the merger agreement, including the financing thereof.

As promptly as practicable after the date of the merger agreement (and in no event no later than 15 business days after the date of the merger agreement), Summit must prepare (with the assistance and cooperation of Quikrete as reasonably requested by Summit) and file or cause to be filed with the SEC this proxy statement. Quikrete and Summit must also cooperate in responding to any comments from the SEC and must use their respective reasonable best efforts to have this proxy statement cleared by the SEC as promptly as reasonably practicable after the filing.

Summit must, as promptly as practicable (and in any event within five business days) following the date the SEC advises that it has no further comments on this proxy statement or that Summit may commence mailing this proxy statement, duly call (including establishing a record date for) and give notice of, and commence mailing of this proxy statement to holders of shares of Summit common stock as of the record date established for, a meeting of such holders to take place within 40 days following the mailing of this proxy statement to Summit stockholders, for purposes of submitting the merger agreement proposal to its stockholders for adoption. The special meeting constitutes that required meeting of the Summit stockholders.

Subject to the ability of the Summit board of directors to make an adverse recommendation change (as defined below), the Summit board of directors is required to recommend to Summit stockholders the adoption of the merger agreement, and Summit is required to include that recommendation in this proxy statement and use reasonable best efforts to obtain from the Summit stockholders the approval of the merger agreement proposal.

Under the terms of the merger agreement, Summit may adjourn or postpone the Summit special meeting (a) with the consent of Quikrete or (b) to the extent Summit believes in good faith (after consultation with outside legal counsel) that such adjournment or postponement is reasonably necessary (i) to ensure that any required supplement

or amendment to the proxy statement is provided to the holders of Summit common stock within a reasonable amount of time in advance of the Summit special meeting, (ii) due to applicable law (including fiduciary duties) or request from the SEC, (iii) to allow reasonable additional time to solicit additional proxies necessary to obtain the Summit stockholder approval or (iv) to allow reasonable additional time to ensure there are sufficient shares of Summit common stock represented and voting to constitute a quorum necessary to conduct the business of the special meeting.

Unless the merger agreement is terminated in accordance with its terms, Summit must submit the merger agreement to its stockholders for adoption at the special meeting even if the Summit board of directors has made an adverse recommendation change.

Without the prior written consent of Quikrete, the adoption of the merger agreement will be the only matter (other than procedural or routine matters and other matters required by applicable law) that Summit may propose to be acted on by Summit’s stockholders at the special meeting. Summit must agree to use reasonable efforts to provide Quikrete periodic updates concerning proxy solicitation results as reasonably requested by Quikrete (including, if requested, providing daily voting reports to the extent reasonably practicable).

Under the terms of the merger agreement, subject to certain exceptions described below, Summit has agreed that, from and after the date of the merger agreement until the earlier of the effective time or the date (if any) the merger agreement is terminated, Summit will not, will cause its subsidiaries as well as Summit’s and its subsidiaries’ respective officers and directors, and Summit’s financial advisors in their capacity as such, not to, and will instruct its and its subsidiaries’ other representatives not to, directly or indirectly: