Amendments to Bylaws Form 8 K

Item 5.03 Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year.

On November 13, 2024, the Board of Directors (the "Board") of Summit Materials, Inc. (the "Company") unanimously approved and adopted the Fourth Amended and Restated Bylaws (as so amended and restated, the "Amended Bylaws") effective as of such date.

The amendment effected by such Amended Bylaws changes the Company's fiscal year from a 52-53 week period ending on the Saturday that is closest to December 31st each year, to the period beginning on January 1st and ending on the 31st day of December in each year. The foregoing description is qualified in its entirety by reference to the full text of the Amended Bylaws, a copy of which is filed as Exhibit 3.1 to this Current Report on Form 8-K and is incorporated herein by reference. In addition, a version of the Amended Bylaws that has been marked to show changes from the bylaws that were previously in effect is included as Exhibit 3.2 to this Current Report on Form 8-K and is incorporated herein by reference.