Elevate Summit: Investor Presentation – May 2022

2022 SUMMIT MATERIALS

INVESTOR DAY

May 24, 2022

Forward Looking Statements

This presentation includes "forward-looking statements" within the meaning of the federal securities laws, which involve risks and uncertainties. Forward-looking statements include all statements that do not relate solely to historical or current facts, and you can identify forward-looking statements because they contain words such as "believes," "expects," "may," "will," "outlook," "should," "seeks," "intends," "trends," "plans," "estimates," "projects" or "anticipates" or similar expressions that concern our strategy, plans, expectations or intentions. All statements made relating to our estimated and projected earnings, margins, costs, expenditures, cash flows, growth rates and financial results are forward-looking statements. These forward-looking statements are subject to risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from future results, performance or achievements expressed or implied by such forward-looking statements. We derive many of our forward-looking statements from our operating budgets and forecasts, which are based upon many detailed assumptions. While we believe that our assumptions are reasonable, it is very difficult to predict the effect of known factors, and, of course, it is impossible to anticipate all factors that could affect our actual results. In light of the significant uncertainties inherent in the forward-looking statements included herein, the inclusion of such information should not be regarded as a representation by us or any other person that the results or conditions described in such statements, or our objectives and plans will be realized. Important factors could affect our results and could cause results to differ materially from those expressed in our forward-looking statements, including but not limited to any factors discussed in the section entitled "Risk Factors" in Summit Materials, Inc.'s ("Summit Inc.") Annual Report on Form 10-K for the fiscal year ended January 1, 2022 as filed with the Securities and Exchange Commission (the "SEC"), and any factors discussed in the section entitled "Risk Factors" in any of our subsequently filed SEC filings and the following: the impact of the coronavirus ("COVID-19") pandemic, or any similar crisis; our dependence on the construction industry and the strength of the economies in which we operate; the cyclical nature of our industry; risks related to weather and seasonality; risks associated with our capital-intensive business; competition within our local markets; our ability to execute on our acquisition and portfolio optimization strategy, successfully integrate acquisitions with our existing operations and retain key employees of acquired businesses; our ability to implement and successfully execute on our Elevate Summit Strategy; our dependence on securing and permitting aggregate reserves in strategically located areas; declines in public infrastructure construction and delays or reductions in governmental funding, including the funding by transportation authorities and other state agencies particularly if such are not augmented by federal funding or if the federal government fails to act on a highway infrastructure bill; our reliance on private investment in infrastructure, which may be adversely affected by periods of economic stagnation and recession; environmental, health, safety and climate change laws or governmental requirements or policies concerning zoning and land use; costs associated with pending and future litigation; rising prices for, or more limited availability of, commodities, labor and other production and delivery inputs as a result of inflation, supply chain challenges, geopolitical events or otherwise; conditions in the credit markets; our ability to accurately estimate the overall risks, requirements or costs when we bid on or negotiate contracts that are ultimately awarded to us; material costs and losses as a result of claims that our products do not meet regulatory requirements or contractual specifications; cancellation of a significant number of contracts or our disqualification from bidding for new contracts; special hazards related to our operations that may cause personal injury or property damage not covered by insurance; unexpected factors affecting self-insurance claims and reserve estimates; our substantial current level of indebtedness, including our exposure to variable interest rate risk; our dependence on our senior management team and our ability to retain and attract qualified personnel; supply constraints or significant price fluctuations in the electricity and petroleum-based resources that we use, including diesel and liquid asphalt; climate change and climate change legislation or other regulations; unexpected operational difficulties; interruptions in our information technology systems and infrastructure, including cybersecurity and data leakage risks; and potential labor disputes, strikes, other forms of work stoppage or other union activities. All subsequent written and oral forward-looking statements attributable to us, or persons acting on our behalf, are expressly qualified in their entirety by these cautionary statements. Any forward-looking statement that we make herein speaks only as of the date of this presentation. We undertake no obligation to publicly update or revise any forward-looking statement as a result of new information, future events or otherwise, except as required by law.

Non-GAAP Financial Measures

Included in this presentation are certain non-GAAP financial measures, such as Adjusted EBITDA, Adjusted EBITDA Margin, Return on Invested Capital, ROIC Margin, Net Debt, Adjusted Cash Gross Profit, Adjusted Cash Gross Profit Margin, Adjusted Diluted Net Income (Loss)and Net Leverage, designed to complement the financial information presented in accordance with U.S. GAAP because management believes such measures are useful to investors. These non-GAAP financial measures should be considered only as supplemental to, and not superior to, financial measures provided in accordance with GAAP. Please refer to the appendix of this presentation for a reconciliation of the historical non-GAAP financial measures included in this presentation to the most directly comparable financial measures prepared in accordance with GAAP.

Reconciliations of the non-GAAP measures used in this presentation are included or described in the tables attached to the appendix. Because GAAP financial measures on a forward-looking basis are not accessible, and reconciling information is not available without unreasonable effort, we have not provided reconciliations for forward-lookingnon-GAAP measures. For the same reasons we are unable to address the probable significance of the unavailable information, which could be material to future results.

Our Agenda

Summit	Elevate Summit & Our	Disciplined Value
Today	Path Ahead	Creation

Safety Share

Chris Gaskill

EVP, Chief Legal Officer

Summit's Story

Anne Noonan

Chief Executive Officer

Elevate Summit Overview &	Disciplined Value Creation
Next Phase of Growth	Brian Harris
Anne Noonan	Chief Financial Officer
Chief Executive Officer	Summary Remarks
Raising the Bar on Talent	Anne Noonan
Deon MacMillan	Chief Executive Officer
EVP, Chief People Officer	Q&A
Sustainability Roadmap
Karli Anderson
EVP, Chief ESG Officer & IR
Building Innovation & Growth
Kekin Ghelani
Chief Growth Officer
Unique Operating Model	3
Regional Presidents

Safety Share

15 years advising public companies

7 years at Summit

Prior Roles:

• Prior inhouse leadership positions at Fortune 500 companies in healthcare and financial services
• Corporate associate at Simpson, Thacher & Bartlett LLP
  Education:
• JD, University of Virginia School of Law
• BA, Government and Legal Studies at Bowdoin College

Other:

• Board of Governors, Colorado Goodwill

Chris Gaskill, EVP, Chief Legal

Officer & Secretary

4

Our Leadership Team

Anne Noonan	Brian Harris	Kekin Ghelani	Karli Anderson	Chris Gaskill	Deon MacMillan
ChiefExecutiveOfficer	ChiefFinancialOfficer	ChiefStrategyand	EVP,ChiefESGOfficer,and	EVP,ChiefLegalOfficer	EVP,Corp.Communications
		GrowthOfficer	Head of InvestorRelations	& Secretary	& ChiefPeopleOfficer

Jeff Perkins	Scott Anderson	Jason Kilgore	David Loomes	Bart Boyd
SouthRegionPresident	CentralRegionPresident	WestRegionPresident	President,CementBusiness	East RegionPresident

5