X0306 4 2016-04-19 0 0001621563 Summit Materials, Inc. SUM 0001440948 Hill Thomas W. C/O SUMMIT MATERIALS, INC. 1550 WYNKOOP STREET, 3RD FLOOR DENVER CO 80202 1 1 0 0 President and CEO Class A Common Stock 2016-04-19 4 C 0 43464 A 53614 D Class A Common Stock 2016-04-19 4 S 0 43464 20.00 D 10150 D Class A Common Stock 40000 I See Footnote LP Units of Summit Materials Holdings L.P. 2016-04-19 4 C 0 43464 D Class A Common Stock 43464 26741 D LP Units of Summit Materials Holdings L.P. Class A Common Stock 1216265 1216265 I See Footnote 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 ("Class A Common Stock") on a one-for-one basis. This amount represents the $20.15 public offering price per share of Class A Common Stock, less the underwriting discount of $0.15 per share. Reflects securities held by a trust for the benefit of Mr. Hill's family, for which Mr. Hill's spouse serves as trustee. The Reporting Person disclaims beneficial ownership of the securities reported herein as indirectly beneficially owned, except to the extent of his pecuniary interest therein. /s/Anne Lee Benedict, as Attorney-in-Fact 2016-04-21