Exhibit 99.1

Summit Materials, Inc. Reports Second Quarter 2017 Results

-Net Revenue Increased 15.9% Y/Y to $478.4 million

-Generated Year-Over-Year Organic Volume Growth Across All Lines of Business

-Completed Four New Acquisitions Since May 2017 For a Combined Purchase Price $130 million

-Raising Full-Year 2017 Adjusted EBITDA Guidance to a Range of $440 million to $455 million

DENVER, CO. - (August 2, 2017) - Summit Materials, Inc. (NYSE: SUM, “Summit” or the “Company”), a leading vertically integrated construction materials company, today announced results for the second quarter 2017. 

For the three months ended July 1, 2017, the Company reported basic earnings per share of $0.47 on net income of $50.0 million, compared to basic earnings per share of $0.21 on net income of $13.4 million in the prior year period.  On an adjusted diluted basis, Summit reported diluted earnings per share of $0.48 on net income of $53.6 million, compared to adjusted diluted earnings per share of $0.45 on net income of $46.2 million in the prior year period.  Operating income increased by 75.6% to $82.4 million in the second quarter 2017, versus $46.9 million in the prior year period.

“We delivered exceptional growth in net revenue, operating income and net income during the second quarter, driven by a combination of strong seasonal demand across all lines of business, together with contributions from recently completed acquisitions,” stated Tom Hill, CEO of Summit Materials.  “Adjusted EBITDA increased 17.9% year-over-year to $135.2 million, supported by favorable market conditions in our West Region and in our Cement Segment.  Organic growth contributed one-third of the year-over-year improvement in Adjusted EBITDA, as supported by ongoing price, volume and cost optimization initiatives at each of our operating companies.”

“Organic sales volumes within our materials lines of business have exceeded our expectations coming into the year,” continued Hill.  “Organic cement and aggregates sales volumes increased 7.1% and 6.1%, respectively, in the second quarter 2017, when compared to the prior year period.  Cement sales volumes in our northern Mississippi River markets increased nearly 25% year-over-year, while aggregates demand in Texas and Utah benefited from a combination of favorable demographic trends and recent state-level funding initiatives that support multi-year investments in transportation infrastructure.”

“Organic cement pricing increased 3.0% year-over-year, in-line with expectations, while organic aggregates pricing declined on a year-over-year basis due to a less favorable sales mix in our Vancouver and Austin markets, given increased sales of lower priced products.  Outside of Austin and Vancouver, organic aggregates pricing increased on a year-over-year basis in nearly all of our other platform markets,” stated Hill.

“We continue to realize superior margin capture throughout our business,” noted Hill.  “Aggregates adjusted cash gross profit margin increased nearly 500 basis points year-over-year to 68.3%, while cement adjusted cash gross profit margin increased 520 basis points year-over-year to 57.4%.  On a trailing twelve month basis through the second quarter 2017, Adjusted EBITDA margin improved by nearly 100 basis points to 24.7%, versus the comparable year period.”

“We have closed on four acquisitions since our last quarterly update in May 2017,” continued Hill.  “Together, these bolt-on transactions expand and enhance our vertically-integrated materials-based businesses in Texas, Kentucky, Colorado and South Carolina.  Given partial-year contributions from these four acquisitions, we have increased our Adjusted EBITDA guidance for the second time this year.  For the full-year 2017, we now forecast total Adjusted EBITDA in the range of $440 million to $455 million, up from the prior range of $430 million to $445 million.” 

“Our acquisition pipeline remains very active, with more than 20 transactions currently under review,” continued Hill.  “On a year-to-date basis, we have invested $309 million across ten transactions, leading us to upwardly revise our annualized acquired EBITDA target from a range of approximately $40 million to $60 million to a range of $50 million to $70 million for the full-year 2017.”

“We ended the second quarter with significant available liquidity on our balance sheet,” stated Brian Harris, CFO of Summit Materials.  “As of July 1, 2017, we had more than $570 million in cash and availability under our revolving credit facility, up from $200 million in the prior year period, due mainly to the completion of a $300 million 5.125% senior notes offering in June 2017.  This opportunistic capital raise allowed us to lower our overall cost of debt, while equipping us to finance the ongoing strategic growth of our business.”

“Net leverage was 3.7x exiting the second quarter 2017, versus 4.5x in the prior year period and down from 3.9x at year-end 2016,” continued Harris.  “Looking ahead, we expect net leverage to be in a range of 3.0x to 3.5x by year-end 2017, assuming the mid-point of our upwardly revised 2017 Adjusted EBITDA guidance.”

“Given continued strength in organic volume growth, record levels of available liquidity and multiple near-term acquisitions on the horizon, Summit is well positioned as we transition into the second half of the year,” concluded Hill.  “We are pleased with our performance in the second quarter and look forward to building on the momentum evident in our business.”

Second Quarter 2017 | Financial Performance

Net revenue increased by 15.9% to $478.4 million in the second quarter 2017, versus $412.6 in the prior year period.  The improvement in net revenue was primarily attributable to acquisition-related contributions, increased organic sales volumes across all lines of business, together with improved organic average selling prices in cement and ready-mix concrete.  Operating income increased by 75.6% to $82.4 million in the second quarter 2017, when compared to the prior year period.  Adjusted EBITDA increased 17.9% year-over-year to $135.2 million, versus $114.7 million in the prior year period.  Adjusted EBITDA margin increased 50 basis points to 28.3% in the second quarter 2017, when compared to the prior year period.

The Company reported an adjusted diluted net income of $0.48 per diluted share in the second quarter 2017, using 111.5 million weighted-average total shares. The shares of Class A common stock are issued by Summit Materials, Inc., and as such the earnings and equity interests of non-controlling interests, including LP units, are not included in basic earnings per share under generally accepted accounting principles.  Management believes excluding non-recurring and non-operating changes provides investors with information that may be more comparable to the financial performance of our peers.

West Segment:  Operating income increased 25.5% to $42.9 million in the second quarter 2017, when compared to the prior year period.  Adjusted EBITDA increased by 19.6% to $60.5 million in the second quarter 2017, when compared to the prior year period.  Adjusted EBITDA margin was 24.2% in the second quarter 2017, flat versus the prior year.  Year-over-year organic improvements in aggregates and ready-mix concrete sales volumes, together with acquisition-related EBITDA contributions, more than offset lower organic asphalt sales volumes and organic declines in average selling prices.

East Segment:  Operating income declined 5.7% to $21.1 million in the second quarter 2017, as increases in depreciation, and to a lesser extent general and administrative expenses, exceeded acquisition-related revenue gains due to the seasonality of the business.  Adjusted EBITDA increased by 8.7% to $38.8 million in the second quarter 2017, when compared to the prior year period.  Adjusted EBITDA margin declined to 26.9% in the second quarter 2017, versus 28.8% in the prior year period.  Year-over-year organic improvements in average selling prices on aggregates and ready-mix concrete, improved organic asphalt sales volumes, together with acquisition-related EBITDA contributions, were offset by organic sales volume declines in aggregates and ready-mix concrete, due in part to weather-related factors.

Cement Segment:  Operating income increased 18.1% to $33.7 million in the second quarter 2017, when compared to the prior year period.  The increase in operating income was primarily due to increased organic growth in sales volumes and pricing.  Adjusted EBITDA increased by 16.5% to $43.8 million in the second quarter 2017, when compared to the prior year period, resulting primarily from pricing improvements and operational efficiencies.  Adjusted EBITDA margin increased to 52.0% in the second quarter 2017, versus 47.2% in the prior year period.  A year-over-year increase in average selling prices, organic sales volumes, improved production efficiencies and cost reductions all contributed to improved results.

Second Quarter 2017 | Results by Line of Business

Aggregates Business:   Aggregates net revenues increased by 15.3% to $84.2 million in the second quarter 2017, when compared to the prior year period.  Aggregates adjusted cash gross profit margin increased to 68.3% in the second quarter 2017, versus 63.3% in the prior year period.  Organic aggregates sales volumes increased 6.1% in the second quarter 2017, due mainly to increased demand in Texas, Utah, Virginia and Vancouver.  Organic aggregates average selling prices declined 1.7% in the second quarter, due in part to an unfavorable sales mix in the Vancouver and Austin markets.  Excluding the Vancouver and Austin markets, organic aggregates average selling prices increased 3.5% on a year-over-year basis.

Cement Business:  Cement segment net revenues increased 5.8% to $84.2 million in the second quarter 2017, when compared to the prior-year period.  Cement adjusted cash gross profit margin was 57.4% in the second quarter 2017, versus 52.2% in the prior-year period.  Organic sales volumes and average selling prices of cement increased 7.1% and 3.0%, respectively, when compared to the prior year period.  Strong regional demand in the Company’s northern markets drove organic volume growth in the second quarter, while continued organic growth in sales prices was attributable to previously announced price increases.    

Products Business:  Net revenues increased 18.3% to $234.6 million in the second quarter 2017, when compared to the prior year period.  Products adjusted cash gross profit margin declined to 25.6% in the second quarter 2017, versus 26.9% in the prior year period.  Organic sales volumes of ready-mix concrete and asphalt increased 9.2% and 3.6%, respectively, when compared to the prior-

year period.  With regard to organic ready-mix sales volumes, demand was strongest in the Houston, Austin, northeast Texas and Kansas markets.  With regard to organic asphalt sales volumes, demand was strongest in the Austin, Kansas and Kentucky markets.

Acquisition Program Update

The Company has completed ten acquisitions on a year-to-date basis, including four transactions that have closed since May 2017.  Total investment spend across the ten acquisitions completed year-to-date 2017 is approximately $309 million, including $130 million for the four acquisitions completed since May 2017. 

Glasscock Company (South Carolina).  Glasscock is a vertically integrated aggregates and ready-mix business serving the East Columbia, South Carolina market.  This acquisition complements Summit’s existing aggregates footprint in central South Carolina.  The Company estimates that Glasscock’s exposure is mainly weighted toward residential and non-residential construction markets, together with some public construction market exposure.  Summit closed on its acquisition of Glasscock in May 2017. 

Great Southern Ready Mix (Texas).  Great Southern is a ready-mix business that provides for further expansion into the north/northeast Houston market.  The Company estimates that Great Southern’s exposure is entirely weighted toward residential and non-residential construction markets.  Summit closed on its acquisition of Great Southern in July 2017.

Ready-Mix Concrete of Somerset (Kentucky).  Ready-Mix Concrete is a ready-mix concrete business serving the central Kentucky region.  The Company estimates that Ready-Mix’s exposure is mainly weighted toward residential and non-residential construction markets, together with some public construction market exposure.    Summit closed on its acquisition of Ready-Mix Concrete in July 2017.

Northwest Ready Mix (Colorado).  Northwest Ready Mix is an aggregates and ready-mix concrete business that allows for further expansion in the intermountain region outside of Steamboat Springs, Colorado.  The Company estimates that Northwest Ready Mix’s exposure is entirely weighted toward residential and non-residential construction markets.  Summit closed on its acquisition of Northwest Ready Mix in July 2017.

Liquidity and Capital Resources

At July 1, 2017, the Company had cash on hand of $353.1 million and borrowing capacity under its revolving credit facility of $218.9 million.  The borrowing capacity on the revolving credit facility is fully available to the Company within the terms and covenant requirements of its credit agreement.  As of July 1, 2017, the Company had $1.8 billion in debt outstanding. 

2017 Financial Guidance & Outlook

The Company is raising its full-year 2017 Adjusted EBITDA guidance from a range of $430.0 million to $445.0 million to a range of $440 million to $455 million.  The upwardly revised Adjusted EBITDA outlook assumes the partial-year impact of the four acquisitions completed since May 2017.  No additional potential acquisitions are included within the Company’s full-year 2017 Adjusted EBITDA guidance.  Including the impact of the ten acquisitions completed on a year-to-date basis, the Company is reiterating its gross capital expenditure guidance of $140 million to $160 million for the full-year 2017.

Webcast and Conference Call Information

Summit Materials will conduct a conference call today at 12:30 p.m. eastern time (10:30 a.m. mountain time) to review the Company’s second quarter 2017 financial results.  A webcast of the conference call and accompanying presentation materials will be available in the Investors section of Summit’s website at investors.summit-materials.com. To listen to a live broadcast, go to the site at least 15 minutes prior to the scheduled start time in order to register, download, and install any necessary audio software.

To participate in the live teleconference:

To listen to a replay of the teleconference, which will be available through September 2, 2017:

About Summit Materials

Summit Materials is a leading vertically integrated materials-based company that supplies aggregates, cement, ready-mix concrete and asphalt in the United States and British Columbia, Canada. Summit is a geographically diverse, materials-based business of scale that offers customers a single-source provider of construction materials and related downstream products in the public infrastructure, residential and nonresidential, and end markets. Summit has a strong track record of successful acquisitions since its founding and continues to pursue growth opportunities in new and existing markets.  For more information about Summit Materials, please visit www.summit-materials.com.  

Non-GAAP Financial Measures

The Securities and Exchange Commission (“SEC”) regulates the use of “non-GAAP financial measures,” such as Adjusted EPS, Adjusted EBITDA, Adjusted EBITDA margin, Adjusted Cash Gross Profit, Adjusted Cash Gross Profit Margin, Free Cash Flow and Net Leverage which are derived on the basis of methodologies other than in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). We have provided these measures because, among other things, we believe that they provide investors with additional information to measure our performance, evaluate our ability to service our debt and evaluate certain flexibility under our restrictive covenants. Our Adjusted Net Income, Adjusted EPS, Adjusted EBITDA, Adjusted EBITDA margin and Adjusted Cash Gross Profit may vary from the use of such terms by others and should not be considered as alternatives to or more important than net income (loss), operating income (loss), revenue or any other performance measures derived in accordance with U.S. GAAP as measures of operating performance or to cash flows as measures of liquidity.

Adjusted EBITDA, Adjusted EBITDA margin and other non-GAAP measures have important limitations as analytical tools, and you should not consider them in isolation or as substitutes for analysis of our results as reported under U.S. GAAP. Some of the limitations of Adjusted EBITDA are that these measures do not reflect: (i) our cash expenditures or future requirements for capital expenditures or contractual commitments; (ii) changes in, or cash requirements for, our working capital needs; (iii) interest expense or cash requirements necessary to service interest and principal payments on our debt; and (iv) income tax payments we are required to make. Because of these limitations, we rely primarily on our U.S. GAAP results and use Adjusted EBITDA, Adjusted EBITDA margin and other non-GAAP measures on a supplemental basis. 

Adjusted EBITDA, Adjusted EBITDA margin, Adjusted Cash Gross Profit, Adjusted Net Income (loss), Adjusted EPS and Free Cash Flow reflect additional ways of viewing aspects of our business that, when viewed with our GAAP results and the accompanying reconciliations to U.S. GAAP financial measures included in the tables attached to this press release, may provide a more complete understanding of factors and trends affecting our business. We strongly encourage investors to review our consolidated financial statements in their entirety and not rely on any single financial measure.

Reconciliations of the non-GAAP measures used in this press release are included in the attached tables.  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.

Cautionary Statement Regarding Forward-Looking Statements

This press release contains “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,” “should,” “seeks,” “intends,” “trends,” “plans,” “estimates,” “projects” or “anticipates” or similar expressions that concern our strategy, plans, expectations or intentions. Any and all statements made relating to the expectations for our anticipated benefits from recent acquisitions, the macroeconomic outlook for our markets, potential acquisition activity, our estimated and projected earnings, margins, costs, expenditures, cash flows, sales volumes and financial results are forward-looking statements. These forward-looking statements are subject to risks and uncertainties that may change at any time, and, therefore, our actual results may differ materially from those expected. 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 impact 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 achieved. 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 our Annual Report on Form 10-K for the fiscal year ended December 31, 2016. Such factors may be updated from time to time in our periodic filings with the SEC, which are accessible on the SEC’s website at www.sec.gov.  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 otherwise required by law.

SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Consolidated Statements of Operations

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Consolidated Balance Sheets

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Consolidated Statements of Cash Flows

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Revenue Data by Segment and Line of Business

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Reconciliations of Gross Revenue to Net Revenue by Line of Business

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Reconciliations of Non-GAAP Financial Measures

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The tables below reconcile our net income (loss) to Adjusted EBITDA by segment for the three and six months ended July 1, 2017 and July 2, 2016 and the twelve months ended July 1, 2017 and July 2, 2016.