UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file numbers: 001-36873 (Summit Materials, Inc.) 333-187556 (Summit Materials, LLC) SUMMIT MATERIALS, INC. SUMMIT MATERIALS, LLC (Exact name ...