#1March 16, 2021 ELEVATE SUMMIT MATERIALS#2Forward-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 the 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 2, 2021 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 on our business, or any similar crisis; our dependence on the construction industry and the strength of the local economies in which we operate; the cyclical nature of our business; 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 strategy, successfully integrate acquisitions with our existing operations and retain key employees of acquired businesses; 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 commodities, labor and other production and delivery inputs as a result of inflation 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 senior management and other key personnel, 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, 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-looking non-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. SUMMIT Materials ELEVATE SUMMIT MATERIALS 2#3We produce the materials foundational to the comforts of life 30,000-100,000 cubic yards of ready-mix concrete, inclusive of 50,000 to 150,000 tons of aggregates 400 tons of aggregates are used to build a new home 3,000 cubic yards of ready-mix concrete are required to build a new school SUMMIT Materials BO THU COMMERCIAL Materials estimates are based on averages at Summit customer locations. RESIDENTIAL M Um www. PUBLIC CLOM DOOR HH 50,000-200,000 tons of aggregates go into the development of a distribution center 85 tons of asphalt required to pave the neighborhood cul de sac 38,000 tons of aggregates are required for one mile of highway ELEVATE SUMMIT MATERIALS 3#4Megatrends Inform and Support our Strategy SUMMIT Materials Sustainability & Social Responsibility GROWTH Performance Needs & Specialty Applications Building the Physical Footprint of Technology PERSISTENT Population Growth and Migration Trends Increased Focus on Infrastructure Spend Constructability ELEVATE SUMMIT MATERIALS 4#5#6MISSION Summit's mission is to provide the foundation to connect our communities today and build a better tomorrow. SUMMIT Materials VISION Summit's vision is to be the most socially responsible, integrated construction materials solution provider, collaborating with stakeholders to deliver differentiated innovations and solve our customers' challenges. VALUES 1. Safety: We are committed to keeping our employees, customers, and communities safe in all that we do. 2. Integrity: We build trust by doing what's right and remaining accountable, even when no one is watching. 3. Sustainability: We answer to the impact of our actions and seek out opportunities to develop innovative practices and solutions. 4. Inclusivity: We act intentionally to bring together our local communities and drive equity for all stakeholders. ELEVATE SUMMIT MATERIALS 6#7Elevate Summit is designed to yield long-term results EBITDA Margin SUMMIT >30% Materials >10% ROIC <3x Leverage ELEVATE SUMMIT MATERIALS 7#8#9Standardization WHAT are we doing differently? Leveraging the full buying power of Summit where we truly benefit from our scale Developing the data tools required to optimize ROIC down to all the lines of business across all of our assets Building a technology strategy to enhance our systems and capabilities across all of Summit WHAT will it get us? Procurement savings & efficiencies More data driven & agile decision making#10#11#12#13#14#15#16#17#18#19#20#21#22#23#24#25#26#27#28#29