0001621563 2020-07-22 2020-07-22 0001621563 false 8-K 2020-07-22 Summit Materials, Inc. DE 001-36873 47-1984212 1550 Wynkoop Street 3rd Floor Denver CO 80202 303 893-0012 false false false false Class A Common Stock (par value, $0.01 per share) SUM NYSE false 2020-07-22 2020-07-22