Q Results Presentation. August 5, 2021

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Q2 2021 Results Presentation

August 5, 2021

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2

Market Leadership

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 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 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 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, 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-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.

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Conference Call Agenda

Safe Harbor Disclosure

Karli Anderson, EVP, ESG & Head of Investor Relations Business Update

Anne Noonan, CEO Financial Update Brian Harris, CFO Management Outlook

Anne Noonan, CEO Q&A

Agenda

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Q2 Results & Elevate Summit Success

1

2 FINANCIAL RESULTS

 Record Net Revenue of $618.5M

 Net Income of $57.8M

 Record Adjusted EBITDA of $163.8M

 Adj Cash Gross Profit Margin of 32.4%

3

4 VOLUME Vs Q2 2020

 Aggregates +14.7%

 Cement +8.3%

 Ready-Mix +6.3%

 Asphalt -11.3% [due primarily to divestiture ]

ELEVATE SUMMIT GOALS

 Leverage improved to 3x, an improvement of 0.2x q/q and 0.5x y/y

 4 divestitures completed in Q2; 5 year to date, $103.6M proceeds

 Expect organic growth to offset divestitures; no change to Outlook

Summit Q2 Record Net Revenue and Adjusted EBITDA

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Cement Segment

Net Revenue of $85.8M, up 13%

Adj EBITDA of $39.4M, up 11%

 Higher cement volume and price

 Green America Recycling continues to ramp to full production; GAR expansion underway

East Segment

Record Net Revenue of $219.1M, up 9%

Adj EBITDA of $57.3M, up 7%

 Higher aggregates and asphalt volume and price partially offset by lower ready-mix on fewer windfarm projects

Kilgore, West Region Cornejo, East Region Continental Cement, Davenport, IA

Q2 2021 Results vs Q2 2020 Reflect Favorable Market Conditions

West Segment

Record Net Revenue of $313.6M, up 5%

Adj EBITDA of $78.8M, in-line

 Higher aggregates and ready-mix volume and

price partially offset by fewer working days for

Texas due to wet conditions

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Market Leadership

Elevate | Themes and Capabilities

Innovative Solutions

to address tomorrow‘s challenges

Market Leader

in advantaged exurban+

markets where we invest and grow for a #1 or #2 market

position

Most Socially Responsible

integrated construction materials solution provider

Asset Light Partnerships

to maximize pull through and reduce volatility in select markets while enhancing EBITDA margin and ROIC

Culture of Excellence

Simplification and Standardization Enabling

Capabilities Core Strategic

Themes

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Market

Leadership Horizon 2

Enhance our Business Models and Offerings Explore creative business models to reduce

downstream capital investment and maximize aggregates pull through

Pursue long-term contracts and supply

agreements to reduce volatility Invest to enter prioritized markets

Horizon 3

Realize and Sustain Consistent Growth Scale successful business models to further reduce liability, volatility.

And reinforce growth in new markets through innovative offerings and solutions with differentiated value

Elevate within the organization and community to attract new talent, investor interest, and new customers

Horizon 1 – WE ARE HERE

Build for Tomorrow with No Regret Moves Manage the business for efficiency

through smart standardization and cultivate a culture of excellence

Divest dilutive businesses to boost margins and free up

capital for growth

Cultivate social responsibility

and innovation expertise EBITDA = 23 – 25% | 9% ROIC

<3x Leverage EBITDA = 25 – 28% |

10% ROIC

<3x Leverage EBITDA = 28 – 30% |

10% ROIC

<3x Leverage

Summit’s long-term financial goals are being pursued through a multi-horizon implementation of the strategy –

Elevate Summit Overview

Objectives

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8

Elevate Summit Scorecard

<3x Leverage

>10%

>30%

ROIC EBITDA

Margin 3.2x

8.0%

22.6%

2020A ¹ Goal

 5 divestitures completed

 Strategic market area and asset light opportunities under consideration

 Smart standardization and centers of excellence being implemented

 Cultivating social responsibility and innovation expertise

8.5%

22.9%

LTM Progress ²

1 The 2020 Actual values for ROIC and EBITDA margin on this chart are slightly lower than values shown on the March 16, 2021 Elevate Summit Strategy Presentation due to a modification in Summit’s reporting for transactions costs that resulted in a reclassification of our 2020 transactions costs.

2 Reflects performance for the last 12 months ended July 3, 2021.

3.0x

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Elevate Summit Portfolio Optimization

Divestitures

Proceeds Unlocked

1Reflects performance for the last 12 months ended July 3, 2021.

Right owner analysis Shed

non-core Convert to Asset Light

$103.6M

Proceeds $15.4M Gain

Divestitures

5

Completed

10-12

Divestitures

>$200M

YTD Progress ¹ Horizon 1 Goal Portfolio Review

Maximize Strategic Flexibility Enter or Expand in

Priority Markets

Achieve Growth objectives

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10

$0

$10

$20

$30

$40

$50

$60

$0

$50

$100

$150

$200

$250

$300

2014-2020 2021 2022 2023 2024

Estimated Capex and Illustrative Incremental Adjusted EBITDA from Greenfields

Cumulative Greenfields CapEx Estimated Incremental Capex Illustrative Incremental Adjusted EBITDA

10

Aggregates Greenfields

An Important Component of our Organic Growth Strategy

We are expanding our presence in key markets:

 5 Aggregates Greenfields completed

 Utah, Texas (3 projects), Georgia

 5 Aggregates Greenfields under development

 Georgia (2), Missouri, Carolinas (2)

 Estimated future Greenfields spending:

 ~$25-35MM in 2021

 ~450 million tons of reserves Recently acquired Aggregates property in Missouri

~$45MM Adjusted EBITDA per year, run rate by 2024

Cap Ex($M) Adjusted EBITDA ($M)

Recently commissioned crushing plant, Georgia, October 2019

(1) Does not include deferred consideration.

Greenfields: Investing for Consistent, Organic Growth

Expanding our presence in the Carolinas in a region experiencing favorable residential and nonresidential growth trends as well as improving state DOT funding conditions

Building on our presence in Georgia with a greenfield startup that occurred in July 2021; strong migration trends, state DOT funding +13%, major mobility program, job growth

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Financial Update

Brian Harris, CFO

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Net Revenue Bridge

Net Revenue by Reporting Segment – Q2 2020 vs. Q2 2021 ($M)

Net Revenue

$575.2

$618.5

$0.2

$14.3

$17.0

$1.5

$10.2

Q2 2020 West - Organic West - Acquisition East - Organic East - Acquisition Cement - Organic Q2 2021

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Adjusted EBITDA Bridge

Adjusted EBITDA by Reporting Segment – Q2 2020 vs Q2 2021 Adjusted EBITDA ($M)

Adjusted EBITDA

$159.9

$163.8

$4.2

$3.6

$0.3

$3.8

$4.3

$3.6

Q2 2020 West - Organic West - Acquisition East - Organic East - Acquisition Cement - Organic Corp - Organic Q2 2021

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Key Performance Indicators

GAAP Financial Metrics

Net Revenue ($M) Operating Income ($M)

Net Income - Summit Inc. ($M) Basic Earnings Per Share

⁽¹⁾

(1) Diluted share count includes all outstanding Class A common stock and LP Units not held by Summit Inc.

$575.2 $618.5

$917.6 $1,017.0

2Q20 2Q21 1H20 1H21

$100.1 $95.9

$58.3 $70.9

2Q20 2Q21 1H20 1H21

$57.1 $56.7

$12.1

$34.1

2Q20 2Q21 1H20 1H21

GAAP Measures

$0.50

$0.48

2Q20 2Q21

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Non-GAAP Measures

Adj. Cash Gross Profit ($M)

& Margin (%)

^(1,2)

Adj. Diluted Earnings(Loss) Per Share

^(1,4)

Adj. EBITDA ($M)

& Margin (%)

^(1,3)

(1) See appendix for reconciliation of these non-GAAP metrics to the most comparable GAAP metrics (2) Adjusted Cash Gross Profit Margin is defined as Adjusted Cash Gross Profit divided by Net Revenue (3) Adjusted EBITDA Margin is defined as Adjusted EBITDA divided by Net Revenue

Adj. Diluted Net Income ($M)

⁽¹⁾

$191.5 $200.2

$241.3

$281.4

2Q20 2Q21 1H20 1H21

$159.9 $163.8 $175.6

$205.5

2Q20 2Q21 1H20 1H21

$58.9 $58.0

$2.6

$19.1

2Q20 2Q21 1H20 1H21

$0.50

$0.49

2Q20 2Q21

33.3% 32.4% 26.3%

27.7%

27.8% 26.5% 19.1%

20.2%

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Aggregates Average Selling Price

(year-over-year % change) Organic Cement Sales Volume and Price

(year-over-year % change)

Sales Volume, Excluding Acquisitions

(year-over-year % change) Sales Volume, Including Acquisitions

(year-over-year % change)

Excluding

Acquisitions Including Acquisitions

Aggregates Ready-Mix

Concrete Asphalt Aggregates Ready-Mix

Concrete Asphalt

1H20 1H21

Volume Price

Price and Volume Analysis

0.6% 0.6%

2.7%

0.5%

5.5%

7.9% 7.2%

4.6%

6.9%

-6.1%

-4.1%

1.6%

9.9%

2.1%

5.5% 7.9% 7.2%

17.3%

6.9%

-6.1%

Volume and Price

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Adjusted Cash Gross Margin Scorecard

Aggregates Business

Adjusted Cash Gross Profit Margin (%)

^(1,2)

Cement Segment

Adjusted Cash Gross Profit Margin (%)

^(1,2)

Products Business

Adjusted Cash Gross Profit Margin (%)

^(1,2)

Services Business

Adjusted Cash Gross Profit Margin (%)

^(1,2)

(1) See reconciliations of Adjusted Cash Gross Profit Margin in the appendix

(2) Adjusted Cash Gross Profit Margin is defined as Adjusted Cash Gross Profit divided by Net Revenue. In this presentation of the data, Adjusted Cash Gross Profit is calculated by line of business, less net cost of revenue by line of business

57.7% 55.9%

49.4% 49.8%

2Q20 2Q21 1H20 1H21

20.6%

18.8%

17.1% 16.7%

2Q20 2Q21 1H20 1H21

50.8% 47.2%

30.5% 32.6%

2Q20 2Q21 1H20 1H21

Adjusted Cash Gross Profit Margin

22.1% 21.1%

13.0%

17.3%

2Q20 2Q21 1H20 1H21

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Capital Structure Overview

18

(2) (2)

 Effective Jan 1, 2021 Fixed Production Overhead(FOH)

(2)

is now reported in cost of revenue

 FOH was previously in G&A

 $29.4M of Q2 2020 reclassed

 Transactions costs are now reported in G&A

 Previously included in operating income (loss)

 0.3M of Q2 2020 reclassed

 Q2 2021 Share Count for Adjusted Diluted EPS

 119.3 million, which includes 117.4 million class A shares and 1.9 million LP Units

Net leverage 3.2x at year end, lowest in Summit’s history

Expense Outlook and Reporting Changes

 For modeling purposes, per quarter in 2021 we expect these expenses will be approximately:

 Interest Expense ~$22 to $24 million

 G&A ~$50-55 million

 DD&A ~$54 to $57 million

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Capital Structure Overview

(2) (2)

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Lowest Q2 leverage in Company history:

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 Ending cash of $469.1M, up over

$215.7M from a year ago

 Leverage ratio 3.0x at 2Q end, down 0.5x from Q2 2020 and lowest in

company history

 <3x leverage is our goal

 Nearly $800M available liquidity

Net leverage 3.2x at year end, lowest in Summit’s history

Capital Structure

($ in Millions) Q2 '20 Q3 '20 Q4 '20 Q1 '21 Q2 '21 Int. Rates Maturity

Cash $253.4 $288.8 $418.2 $359.7 $469.1 0.04% n/a

Debt:

Revolver¹ -- -- -- -- -- 3.39% Feb-2024

Senior Secured Term Loan $621.1 $619.5 $616.3 $614.7 $613.1 2.10% Nov-2024

Capital Leases and Other $57.4 $59.8 $56.3 $47.0 $40.4 5.50% Various

Senior Secured Debt $678.5 $679.3 $672.6 $661.7 $653.6 2.31%

Acq.-related Liab. $42.3 $42.5 $20.1 $44.4 $46.3 10.00% Various

5.125% Senior Notes $300.0 $300.0 $300.0 $300.0 $300.0 5.125% Jun-2025

5.25% Senior Notes -- $700.0 $700.0 $700.0 $700.0 5.25% Jan-2029

6.5% Senior Notes $300.0 $300.0 $300.0 $300.0 $300.0 6.50% Mar-2027

6.125% Senior Notes $650.0 -- -- -- -- 6.125% n/a

Senior Unsecured Debt $1,292.3 $1,342.5 $1,320.1 $1,344.4 $1,346.3 5.66%

Total Debt $1,970.8 $2,021.7 $1,992.7 $2,006.1 $1,999.9 4.57%

Net Senior Secured Debt $425.1 $390.5 $254.5 $302.0 $184.5

Net Total Debt $1,717.4 $1,733.0 $1,574.5 $1,646.4 $1,530.8

Est. Annual Cash Int. Run Rate $97.3 $94.1 $91.7 $93.3 $93.1

LTM Further Adj. EBITDA $491.1 $490.2 $496.5 $517.5 $509.4

Net Senior Secured Leverage 0.9x 0.8x 0.5x 0.6x 0.4x

Total Net Leverage 3.5x 3.5x 3.2x 3.2x 3.0x

1 Revolver Capacity post-usage for (undrawn) Letters of Credit is $329.1M as of 7/3/21

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Management Outlook

Anne Noonan, CEO

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2021 Outlook

Midpoint of Guidance Suggests ~5% Adjusted EBITDA growth despite non-res uncertainty

Assumptions Underpinning Outlook:

 Low- to mid-single-digit pricing increases

 Low single digit volume increases

 Organic growth expected to offset divestiture impacts Current End Market Conditions:

 Residential demand strong

 Non-residential not yet returning to pre-COVID levels

 Public sector funding resilient but we haven’t yet seen effects of stimulus funds to states

$M A djus ted EB IT DA

$462

$485 $490

$520

$420

$440

$460

$480

$500

$520

$540

2019A 2020A 2021E Low 2021E High

2021 Adjusted EBITDA Outlook

$490M-$520M

$177 $177 $175 $185

$25 $35

$0

$50

$100

$150

$200

$250

2019A 2020A 2021E Low 2021E High

2021 Capex Outlook

$200-$220M

(incl $25-$35M for Greenfields) Includes some 2020 deferrals

Greenfields

2021 Outlook

$M

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Market Leadership

Our Elevate Strategy Designed to Deliver Superior Long-Term Value

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Market Leadership

Appendix

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EXHIBIT 2

Reconciliation of Operating Income to Adjusted Cash Gross Profit

24 (1) Adjusted Cash Gross Profit Margin defined as Adjusted Cash Gross Profit divided by Net Revenue

Exhibit 1

July 3, June 27, July 3, June 27,

Reconciliation of Operating Income to Adjusted Cash Gross Profit

²⁰²¹ ²⁰²⁰ ²⁰²¹ ²⁰²⁰

($ in thousands)

Operating income $ 95,923 $ 100,060 $ 70,864 $ 58,340

General and administrative expenses 47,448 39,727 99,090 81,413 Depreciation, depletion, amortization and accretion 58,233 53,928 114,569 105,706 Gain on sale of property, plant and equipment (1,403) (2,214) (3,172) (4,131)

Adjusted Cash Gross Profit (exclusive of items shown separately) $ 200,201 $ 191,501 $ 281,351 $ 241,328 Adjusted Cash Gross Profit Margin (exclusive of items shown separately) (1) 32.4% 33.3% 27.7% 26.3%

Three months ended Six months ended

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EXHIBIT 3

Reconciliation of Gross Revenue to Net Revenue by LOB

Exhibit 2

Volumes

Aggregates 17,091 $ 11.39 $ 194,595 $ (41,099) $ 153,496 Cement 708 119.64 84,673 (2,504) 82,169

Materials $ 279,268 $ (43,603) $ 235,665

Ready-mix concrete 1,534 119.94 183,936 (75) 183,861 Asphalt 1,557 59.87 93,246 (82) 93,164

Other Products 103,259 (88,149) 15,110

Products $ 380,441 $ (88,306) $ 292,135

Elimination/Delivery Revenue

Pricing by Product

Three months ended July 3, 2021

Gross Revenue Intercompany Net

Volumes

Aggregates 30,600 $ 11.06 $ 338,389 $ (67,505) $ 270,884 Cement 1,048 118.68 124,376 (4,068) 120,308

Materials $ 462,765 $ (71,573) $ 391,192

Ready-mix concrete 2,872 119.18 342,272 (178) 342,094 Asphalt 2,031 59.91 121,667 (140) 121,527

Other Products 177,141 (149,920) 27,221

Products $ 641,080 $ (150,238) $ 490,842

Elimination/Delivery Revenue

Pricing by Product

Six months ended July 3, 2021

Gross Revenue Intercompany Net

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26

EXHIBIT 4

Reconciliation of Net Income to Further Adjusted EBITDA

26

(1) Last twelve month (“LTM”) information corresponding to fiscal years (i.e., the periods ended January 2, 2021, December 28, 2019 and December 29, 2018 and reflects our audited historical results for such fiscal years presented in accordance with U.S. GAAP.

Information presented for other LTM periods (i.e., July 3, 2021, April 3, 2021, September 26, 2020, June 27, 2020, March 28, 2020, September 28, 2019, June 29, 2019 and March 30, 2019) reflect unaudited trailing four quarter financial information calculated by starting with the results from the most recent audited fiscal year included in such LTM period and then (x) adding quarterly information for subsequent fiscal quarters and (y) subtracting quarterly information for the corresponding prior year period. For example, LTM July 3, 2021 has been calculated by starting with the data from the twelve months ended January 2, 2021 and then adding data for the six months ended July 3, 2021, followed by subtracting data for the six months ended June 27, 2020. This presentation is not in accordance with U.S. GAAP. However, we believe this information is useful to investors as we use it to evaluate our financial performance for ongoing planning purposes, including a continuous assessment of our financial performance in comparison to budgets and internal projections.

We also use such LTM financial data to test compliance with covenants under our senior secured credit facilities. This presentation has limitations as an analytical tool, and you should not consider it in isolation or as a substitute for analysis of our results as reported under U.S. GAAP. Please see our Annual Reports on Form 10-K and Quarterly Reports on Form 10-Q for the relevant periods for the historical amounts used to calculate the LTM information presented.

(2) EBITDA for certain completed acquisitions, net of dispositions, is pro forma for all acquisitions completed as of the date listed.

(3) Further Adjusted EBITDA is calculated using trailing four quarter financial data to test compliance with covenants under our senior secured credit facilities.

(4) Adjusted EBITDA Margin defined as Adjusted EBITDA as a percentage of net revenue (5) Net Leverage defined as net debt divided by Further Adjusted EBITDA

Exhibit 3

($ in millions) July 3, June 27, July 3, June 27, July 3, April 3, January 2, September 26, June 27, March 28, December 28, September 28, June 29, March 30,

2021 2020 2021 2020 2021 2021 2021 2020 2020 2020 2019 2019 2019 2019

Net income (loss) $ 58 $ 59 $ 35 $ 12 $ 164 $ 165 $ 141 $ 141 $ 107 $ 86 $ 61 $ 6 $ 22 $ 21

Interest expense 24 26 48 53 99 100 104 106 110 114 117 118 118 118

Income tax (benefit) expense 18 17 13 (6) 7 5 (12) (42) 23 22 17 78 53 48

Depreciation, depletion, amortization, and accretion expense 58 54 115 106 230 226 222 216 214 213 217 218 217 214

Loss on debt financings - - - - 4 4 4 4 - - 15 15 15 15

Gain on sale of business - - (15) - (15) (16) - - - - - - (12) (12)

Tax receivable agreement expense - - - - (8) (8) (8) 16 16 16 16 (23) (23) (23)

Non-cash compensation 5 5 10 10 29 29 29 28 20 19 20 21 22 23

Other 1 (1) - 1 2 3 2 4 (2) (1) (4) (1) (2) -

Adjusted EBITDA $ 164 $ 160 $ 206 $ 176 $ 512 $ 508 $ 482 $ 473 $ 488 $ 469 $ 459 $ 432 $ 410 $ 404

EBITDA for certain completed acquisitions, net of dispositions (2) (5) 6 11 15 - - - - - 1

Acquisition transaction expenses 2 3 3 2 3 2 2 2 2 3

Further Adjusted EBITDA (3) $ 509 $ 517 $ 496 $ 490 $ 491 $ 471 $ 461 $ 434 $ 412 $ 408 Net Revenue $ 619 $ 575 $ 1,017 $ 918 $ 2,234 $ 2,191 $ 2,135 $ 2,069 $ 2,090 $ 2,067 $ 2,031 $ 1,969 $ 1,929 $ 1,925

Adjusted EBITDA Margin (4) 26.5% 27.8% 20.2% 19.1% 22.9% 23.2% 22.6% 22.9% 23.4% 22.7% 22.6% 21.9% 21.3% 21.0%

Net Debt $ 1,530 $ 1,646 $ 1,574 $ 1,732 $ 1,717 $ 1,774 $ 1,667 $ 1,820 $ 1,938 $ 1,940

Total Net Leverage (5) 3.0x 3.2x 3.2x 3.5x 3.5x 3.8x 3.6x 4.2x 4.7x 4.8x

Three months ended Six months ended Last Twelve Months Ended (1)

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EXHIBIT 5

Non-GAAP Reconciliation of Long-Term Debt to Net Debt

Exhibit 4

Reconciliation of Long-term Debt to Net Debt

($ in millions)

Q2'21 Q1'21 Q4'20 Q3'20 Q2'20 Q1'20 Q4'19 Q3'19 Q2'19 Q1'19 Q4'18

Long-term debt, including current portion $ 1,913 $ 1,915 $ 1,916 $ 1,919 $ 1,871 $ 1,873 $ 1,874 $ 1,876 $ 1,876 $ 1,877 $ 1,831 Acquisition related liabilities 46 44 20 42 42 42 48 71 71 72 77 Finance leases and other 40 47 56 60 57 58 56 56 59 56 49 Less: Cash and cash equivalents (469) (360) (418) (289) (253) (199) (311) (183) (68) (65) (129)

Net debt $ 1,530 $ 1,646 $ 1,574 $ 1,732 $ 1,717 $ 1,774 $ 1,667 $ 1,820 $ 1,938 $ 1,940 $ 1,828

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28

EXHIBIT 6

Non-GAAP Reconciliation of Net Income (Loss) to Adj. EBITDA

(1) Adjusted EBITDA Margin is defined as Adjusted EBITDA as a percentage of net revenue 28

Exhibit 5

Reconciliation of Net Income (Loss) to Adjusted EBITDA by Segment

($ in thousands)

Net income (loss) $ 55,447 $ 37,035 $ 33,230 $ (67,954) $ 57,758

Interest expense (income) (2,860) (2,176) (4,035) 33,287 24,216

Income tax expense 1,198 156 — 17,054 18,408

Depreciation, depletion and amortization 25,133 21,146 10,143 1,101 57,523

EBITDA $ 78,918 $ 56,161 $ 39,338 $ (16,512) $ 157,905

Accretion 218 408 84 — 710

(Gain) loss on sale of businesses (273) 509 — — 236

Non-cash compensation — — — 4,827 4,827

Other (92) 206 — — 114

Adjusted EBITDA $ 78,771 $ 57,284 $ 39,422 $ (11,685) $ 163,792

Adjusted EBITDA Margin (1) 25.1% 26.1% 45.9% 26.5%

East Cement Corporate Consolidated

West

Three months ended July 3, 2021

($ in thousands)

Net income (loss) $ 57,040 $ 32,206 $ 29,386 $ (59,745) $ 58,887

Interest expense (709) (433) (3,116) 29,866 25,608

Income tax expense (benefit) 1,054 (36) — 16,163 17,181 Depreciation, depletion and amortization 22,050 21,014 9,291 992 53,347

EBITDA $ 79,435 $ 52,751 $ 35,561 $ (12,724) $ 155,023

Accretion 115 380 86 — 581

Other (607) 253 — (229) (583)

Adjusted EBITDA $ 78,943 $ 53,384 $ 35,647 $ (8,061) $ 159,913

Cement East

Three months ended June 27, 2020

Corporate Consolidated West

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EXHIBIT 6

Non-GAAP Reconciliation of Net Income (Loss) to Adj. EBITDA

Exhibit 6

($ in thousands)

Net income (loss) $ 72,883 $ 44,004 $ 31,625 $ (113,999) $ 34,513

Income tax expense 1,384 90 — 11,491 12,965

Depreciation, depletion and amortization 50,057 42,620 18,211 2,205 113,093

EBITDA $ 119,432 $ 82,818 $ 41,756 $ (35,033) $ 208,973

Accretion 434 877 165 — 1,476

Gain on sale of businesses (273) (15,159) — — (15,432)

Other (174) 493 — — 319

Adjusted EBITDA $ 119,419 $ 69,029 $ 41,921 $ (24,843) $ 205,526

Six months ended July 3, 2021

West East Cement Corporate Consolidated

($ in thousands)

Net income (loss) $ 57,538 $ 21,139 $ 17,108 $ (83,624) $ 12,161

Income tax expense (benefit) 587 (165) — (6,142) (5,720) Depreciation, depletion and amortization 43,734 41,734 17,099 1,981 104,548

EBITDA $ 100,572 $ 61,706 $ 27,915 $ (25,778) $ 164,415

Accretion 231 756 171 — 1,158

Other 608 495 — (899) 204

Adjusted EBITDA $ 101,411 $ 62,957 $ 28,086 $ (16,880) $ 175,574

Six months ended June 27, 2020

West East Cement Corporate Consolidated

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30

EXHIBIT 8

Non-GAAP Reconciliation of Net Income to Adj. Diluted Net Income

30

Exhibit 7

(In thousands, except share and per share amounts)

Net income attributable to Summit Materials, Inc. $ 56,659 $ 0.47 $ 57,064 $ 0.49 $ 34,142 $ 0.29 $ 12,085 $ 0.10 Adjustments:

Net income attributable to noncontrolling interest 1,099 0.02 1,823 0.01 371 — 76 —

Loss (gain) on sale of businesses 236 — — — (15,432) (0.13) — —

Adjusted diluted net income before tax related adjustments 57,994 0.49 58,887 0.50 19,081 0.16 12,161 0.10

Changes in unrecognized tax expense (benefit) — — — — — — (9,537) (0.08)

Adjusted diluted net income $ 57,994 $ 0.49 $ 58,887 $ 0.50 $ 19,081 $ 0.16 $ 2,624 $ 0.02

Weighted-average shares:

Basic Class A common stock 117,436,461 114,111,204 116,423,833 113,856,657

LP Units outstanding 1,885,789 3,053,115 2,249,499 3,103,672

Total equity units 119,322,250 117,164,319 118,673,332 116,960,329

Per Equity Unit Net Income Per Equity Unit Net Income Per Equity Unit Net Income Per Equity Unit Net Income

Three months ended Six months ended

Reconciliation of Net Income Per Share to

Adjusted Diluted EPS July 3, 2021 June 27, 2020 July 3, 2021 June 27, 2020

(31)

EXHIBIT 9

Non-GAAP Reconciliation of Adj. Cash Gross Profit by LOB

(1) Net revenue for the cement line of business excludes revenue associated with hazardous and non-hazardous waste, which is processed into fuel and used in the cement plants and is included in services net revenue.

Additionally, net revenue from cement swaps and other cement-related products are included in products net revenue.

(2) Adjusted cash gross profit calculated as net revenue by line of business less net cost of revenue by line of business. Adjusted cash gross profit margin is defined as adjusted cash gross profit divided by net revenue.

Exhibit 8

($ in thousands) Segment Net Revenue:

West $ 313,617 $ 299,024 $ 548,361 $ 483,516

East 219,091 200,554 342,159 320,543

Cement 85,822 75,662 126,491 113,587

Net Revenue $ 618,530 $ 575,240 $ 1,017,011 $ 917,646

Line of Business - Net Revenue:

Materials

Aggregates $ 153,496 $ 129,989 $ 270,884 $ 226,150

Cement (1) 82,169 73,293 120,308 106,156

Products 292,135 284,978 490,842 461,261

Total Materials and Products 527,800 488,260 882,034 793,567

Services 90,730 86,980 134,977 124,079

Net Revenue $ 618,530 $ 575,240 $ 1,017,011 $ 917,646

Line of Business - Net Cost of Revenue:

Materials

Aggregates $ 67,734 $ 54,942 $ 136,031 $ 114,465

Cement 41,672 34,894 79,032 71,549

Products 237,343 226,168 408,963 382,385

Total Materials and Products 346,749 316,004 624,026 568,399

Services 71,580 67,735 111,634 107,919

Net Cost of Revenue $ 418,329 $ 383,739 $ 735,660 $ 676,318

Line of Business - Adjusted Cash Gross Profit (2):

Materials

Aggregates $ 85,762 $ 75,047 $ 134,853 $ 111,685

Cement (3) 40,497 38,399 41,276 34,607

Products 54,792 58,810 81,879 78,876

Services 19,150 19,245 23,343 16,160

Adjusted Cash Gross Profit $ 200,201 $ 191,501 $ 281,351 $ 241,328 Adjusted Cash Gross Profit Margin (2)

Materials

Aggregates 55.9% 57.7% 49.8% 49.4%

Cement (3) 47.2% 50.8% 32.6% 30.5%

Products 18.8% 20.6% 16.7% 17.1%

Services 21.1% 22.1% 17.3% 13.0%

Total Adjusted Cash Gross Profit Margin 32.4% 33.3% 27.7% 26.3%

Three months ended July 3, June 27,

2021 2020

June 27, Six months ended

2021 2020

July 3,

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32

EXHIBIT 10

Free Cash Flow

32

Exhibit 9

($ in thousands)

Net income $ 57,758 $ 58,887 $ 34,513 $ 12,161

Non-cash items 74,221 74,346 113,065 110,013

Net income adjusted for non-cash items 131,979 133,233 147,578 122,174 Change in working capital accounts (36,010) (32,601) (72,927) (60,473)

Net cash provided by operating activities 95,969 100,632 74,651 61,701 Capital expenditures, net of asset sales (58,823) (40,448) (125,917) (99,117)

Free cash flow $ 37,146 $ 60,184 $ (51,266) $ (37,416) July 3, June 27,

2021 2020 2021 2020

July 3, June 27,

Six months ended

Three months ended

(33)

EXHIBIT 11

Capital Structure

Exhibit 10

($ in Millions) Q2 '20 Q3 '20 Q4 '20 Q1 '21 Q2 '21 Int. Rates Maturity

Cash $253.4 $288.8 $418.2 $359.7 $469.1 0.04% n/a

Debt:

Revolver

¹

-- -- -- -- -- 3.39% Feb-2024

Senior Secured Term Loan $621.1 $619.5 $616.3 $614.7 $613.1 2.10% Nov-2024

Capital Leases and Other $57.4 $59.8 $56.3 $47.0 $40.4 5.50% Various

Senior Secured Debt $678.5 $679.3 $672.6 $661.7 $653.6 2.31%

Acq.-related Liab. $42.3 $42.5 $20.1 $44.4 $46.3 10.00% Various

5.125% Senior Notes $300.0 $300.0 $300.0 $300.0 $300.0 5.125% Jun-2025

5.25% Senior Notes -- $700.0 $700.0 $700.0 $700.0 5.25% Jan-2029

6.5% Senior Notes $300.0 $300.0 $300.0 $300.0 $300.0 6.50% Mar-2027

6.125% Senior Notes $650.0 -- -- -- -- 6.125% n/a

Senior Unsecured Debt $1,292.3 $1,342.5 $1,320.1 $1,344.4 $1,346.3 5.66%

Total Debt $1,970.8 $2,021.7 $1,992.7 $2,006.1 $1,999.9 4.57%

Net Senior Secured Debt $425.1 $390.5 $254.5 $302.0 $184.5

Net Total Debt $1,717.4 $1,733.0 $1,574.5 $1,646.4 $1,530.8

Est. Annual Cash Int. Run Rate $97.3 $94.1 $91.7 $93.3 $93.1

LTM Further Adj. EBITDA $491.1 $490.2 $496.5 $517.5 $509.4

Net Senior Secured Leverage 0.9x 0.8x 0.5x 0.6x 0.4x

Total Net Leverage 3.5x 3.5x 3.2x 3.2x 3.0x

1 Revolver Capacity post-usage for (undrawn) Letters of Credit is $329.1M as of 7/3/21

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34

Salt Lake City, UT Strategic Priorities

Market Leadership

1