#1SUMMIT Materials Summit Materials Cement Education Series June 29, 2023#2Cautionary Statement SUMMIT Materials 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 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 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: 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; the impact of the coronavirus ("COVID-19") pandemic, or any similar crisis declines in public infrastructure construction and delays or reductions in governmental funding; 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 other 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 and Adjusted EBITDA Margin, 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. 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.#3Agenda 01 02 03 Opening Remarks 5-10 minutes Barclay's led Q&A 10-15 minutes Open Q&A 5-10 minutes SUMMIT Materials ELEVATE SUMMIT MATERIALS 3#4Cement Background Operational Strength Paired with Industry & Market Growth Standalone Leading Brand CONTINENTA CEMENT Davenport, IA Hannibal, MO 2 Cement Plants 9 Cement Terminals Fundamentals & Top Business Initiatives Tons Sold Import 15% Hannibal 42% Davenport 43% End-Market Mix Agri 9% Public 22% Resi 29% Non Res 40% SUMMIT Sales by Modality Rail 13% Materials Cust. Pickup 34% Barge 53% Carbon Reduction & Expanding Green America Recycling Improving Plant Performance Sharp Commercial Execution North Star Objective: +40% LTM Adjusted EBITDA Margins#5SUMMIT Materials Q&A#611881 SUMMIT Materials Appendix#7Cement Leadership Team David Loomes, President, Cement Business David joined Continental Cement in 2020, becoming President in the first quarter of 2022. In addition to his more than 25 years of experience with Holcim - encompassing senior leadership roles in finance, operations, supply chain, M&A, and sales - David has been instrumental in developing the PCA's road map to carbon neutrality and currently serves on the board of the Portland Cement Association and Inland Waterways Commission. Prior to Summit, David held senior leadership positions in Suffolk Construction Company. Nic Marks, Senior Technical Director SUMMIT Materials Nic joined Continental Cement in 2018 as Director of Technical services before later being promoted to Senior Technical Director in 2021. In his current role, Nic provides technical oversight for cement operations, supports Green America Recycling and leads sustainability and innovation initiatives for Continental. Prior to joining CCC, Nic gained extensive experience in the cement industry during his 14 years with Holcim leading Process, Quality, and Operations teams at multiple sites. Nic is also a Six Sigma Black Belt.#8Site Map | Hannibal River Silo Main Entrance Continental (C) C1-Main Office C2- Electrical Building C3-Maintenance/storehouse C4-Women's Locker room CS-Auto Garage C6-Control Room Building RP C7-Kiln Tower C8-Yard Dept. C9-Syngyp. Building C10-Raw Building C11-Silos C12-Packhouse G9 G8 RP RP Green America Recycling (G) G1-Tank Farm G2-Feed Prep 1&2 G3-Locker room G4-Feed Barn G5-Maintenance G6-Triple Wide C10 G8-Customer Service G9-Railpad Old Storehouse Fred Weber Rally Points (RP) Rear Entrance Underground Mine SUMMIT Materials 8#9Site Map | Davenport A- Plant Entrance B-Shipping Entrance C- Preblend Dome D- Main office E-Preheat Tower F-Warehouse G- New GAR Expansion H- Concrete Lab 1- Gar Tank Farm K- Maintenance Shop L- Cement Silos M- Shipping Office N-Rail/Truck Scale O- Cement Dome O P- Barge Silos Q- Mobile Maintenance Shop R- Quarry Breakroom S- Additive Storage T-Elec. Breakroom & Main Conference Room SUMMIT Materials 9