UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No.     )

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o	Definitive Proxy Statement
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o	Soliciting Material under §240.14a-12
Summit Materials, Inc.
(Name of Registrant as Specified In Its Charter)
(Name of Person(s) Filing Proxy Statement, if other than the Registrant)
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*** Exercise Your Right to Vote *** Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting to Be Held on May 22, 2019 SUMMIT MATERIALS, INC. Date: May 22, 2019 Time: 8:00 AM EDT 777 South Flagler Drive West Palm Beach, FL 33401 You are receiving this communication because you hold shares in the above named company. This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. 1234567 1234567 Envelope # # of # Sequence # 1 OF 2 12 15 0000412244_1 R1.0.1.18 Broadridge Internal Use Only Job # Sequence # See the reverse side of this notice to obtain proxy materials and voting instructions. BROADRIDGE CORPORATE ISSUER SOLUTIONS C/O SUMMIT MATERIALS, INC. P.O. BOX 1342 BRENTWOOD, NY 11717 Investor Address Line 1 Investor Address Line 2 Investor Address Line 3 Investor Address Line 4 Investor Address Line 5 John Sample 1234 ANYWHERE STREET ANY CITY, ONA1A 1A11234567 1234567 1234567 234567 Meeting Information Meeting Type: Annual Meeting For holders as of: March 25, 2019 Location: The offices of Greenberg Traurig Suite 300 East B A R C O D E

Before You Vote How to Access the Proxy Materials Proxy Materials Available to VIEW or RECEIVE:  Have the information that is printed in the box marked by the arrow (located on the  by the arrow (located on the following page) in the subject line. How To Vote Please Choose One of the Following Voting Methods  marked by the arrow available and follow the instructions. Only 0000412244_2 R1.0.1.18 Vote In Person: Many stockholder meetings have attendance requirements including, but not limited to, the possession of an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares. Vote By Internet: To vote now by Internet, go to www.proxyvote.com. Have the information that is printed in the box Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card. Internal Use 1. Notice & Proxy Statement2. Annual Report How to View Online: following page) and visit: www.proxyvote.com. How to Request and Receive a PAPER or E-MAIL Copy: If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request: 1) BY INTERNET: www.proxyvote.com 2) BY TELEPHONE: 1-800-579-1639 3) BY E-MAIL*: sendmaterial@proxyvote.com * If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before May 08, 2019 to facilitate timely delivery.

The Board of Directors recommends you vote "FOR" the following: 1. Election of Directors Nominees 01) Thomas W. Hill 02) Joseph S. Cantie 03) Anne M. Cooney The Board of Directors recommends you vote "FOR" proposals 2 and 3. 2. Nonbinding advisory vote on the compensation of our named executive officers for 2018. 3. Ratification of the appointment of KPMG LLP as our independent auditors for 2019. NOTE: Such other business as may properly come before the meeting or any adjournment or postponement thereof. xxxxxxxxxx Cusip Envelope # # of # Sequence # 0000412244_3 R1.0.1.18 Broadridge Internal Use Only xxxxxxxxxx Job # Sequence # B A R C O D E 23456789012 2 2 2 2 12345678901 12345678901 12345678901 12345678901 12345678901 12345678901 12345678901 12345678901 12345678901 12345678901 Voting items

THE COMPANY NAME INC. - CLASS A THE COMPANY NAME INC. - CLASS C 123,456,789,012.12345 123,456,789,012.12345 THE COMPANY NAME INC. - CLASS F 123,456,789,012.12345 Envelope # # of # Sequence # 0000412244_4 R1.0.1.18 Broadridge Internal Use Only THIS SPACE RESERVED FOR SIGNATURES IF APPLICABLE Job # Sequence # NAME THE COMPANY NAME INC. - COMMON 123,456,789,012.12345 THE COMPANY NAME INC. - CLASS B123,456,789,012.12345 THE COMPANY NAME INC. - CLASS D123,456,789,012.12345 THE COMPANY NAME INC. - CLASS E123,456,789,012.12345 THE COMPANY NAME INC. - 401 K123,456,789,012.12345 Reserved for Broadridge Internal Control Information