X0306 4 2016-04-19 0 0001621563 Summit Materials, Inc. SUM 0001228680 GARDNER TED A C/O SUMMIT MATERIALS, INC. 1550 WYNKOOP STREET, 3RD FLOOR DENVER CO 80202 1 0 0 0 Class A Common Stock 2016-04-19 4 C 0 50000 A 50000 I See Footnote Class A Common Stock 2016-04-19 4 S 0 50000 20.00 D 0 I See Footnote Class A Common Stock 2016-04-19 4 C 0 522804 A 522804 I See Footnote Class A Common Stock 2016-04-19 4 S 0 522804 20.00 D 0 I See Footnote LP Units of Summit Materials Holdings L.P. 2016-04-19 4 C 0 50000 D Class A Common Stock 50000 202752 I See Footnote LP Units of Summit Materials Holdings L.P. 2016-04-19 4 C 0 522804 D Class A Common Stock 522804 1611022 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. Reflects securities held by a limited liability company controlled by Mr. Gardner. 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 certain investment funds affiliated with Silverhawk Summit, L.P. ("Silverhawk"). Mr. Gardner, a managing partner and co-founder of Silverhawk, may be deemed to have beneficial ownership of the securities of the issuer held by Silverhawk. 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