X0206 3 2016-01-03 0 0001621563 Summit Materials, Inc. SUM 0001661446 Beck Thomas A. C/O SUMMIT MATERIALS, INC 1550 WYNKOOP STREET, 3RD FLOOR DENVER CO 80202 0 1 0 0 See Remarks LP Units of Summit Materials Holdings L.P. Common Stock 26949 D Options (right to buy) 18.00 2025-03-11 Common Stock 11877 D Options (right to buy) 18.00 2025-03-11 Common Stock 15440 D Pursuant to the terms of an exchange agreement, dated as of March 11, 2015, the limited partnership units of Summit Materials Holdings L.P. ("LP Units") reported herein are exchangeable from and after the first anniversary of the closing of the issuer's initial public offering (subject to the terms of the exchange agreement and vesting requirements, including certain vesting events more fully described in the Issuer's Registration Statement on Form S-1 (File No. 333-201058)) for shares of the issuer's Class A common stock on a one-for-one basis. The options vest in four equal annual installments beginning on March 11, 2016. The options vest upon the achievement of certain vesting events more fully described in the Issuer's Registration Statement on Form S-1 (File No. 333-201058). Title: Executive Vice President and President of Continental Cement Company, L.L.C. Exhibit 24 - Power of Attorney /s/ Anne Lee Benedict, as Attorney-in-Fact 2016-01-12