Exhibit 99.1

Summit Materials Announces Second Quarter 2015 Results

Denver, Colorado (August 3, 2015) — Summit Materials, Inc. (NYSE: SUM, “Summit” or the “Company”), a leading vertically integrated construction materials company, today announced results for the second quarter ended June 27, 2015.

Second Quarter 2015 Highlights Compared to Second Quarter 2014:

Recent Developments:

Tom Hill, the President and CEO of Summit, stated, “During the second quarter we produced significant growth in net revenues and margins across all of our lines of business. This strong improvement reflects the steady demand improvement in all of our regions, despite some weather-related challenges, mainly in Texas and Kansas, and our disciplined focus on price optimization across our vertically integrated lines of businesses. We achieved this while also expanding our Further Adjusted EBITDA margin by 300 basis points and generating incremental margins in excess of 50%. The success of our acquisition strategy was also evident in our results with more than half of our profit growth contributed by our accretive acquisitions, including the recent strategic bolt on addition of Lewis & Lewis, a vertically integrated aggregates-based business, in our West region.”

Mr. Hill continued, “We believe our sustained progress is a direct result of the steps we have taken to expand our business into attractive markets and establish leadership positions throughout our diversified footprint. Our completion of the Davenport Assets acquisition was an exciting milestone for our company and significantly advanced our position as a leading cement producer in the Midwest. We are now better positioned to continue enhancing our materials earnings exposure and overall profitability as we integrate these assets onto our platform. As we look to the back half of 2015, we plan to capitalize on the improving demand environment to improve our profitability while also remaining opportunistic with our capital to further expand our businesses in select target markets.”

Second Quarter 2015 Operating Results

In the second quarter 2015, net revenue increased 12.5% to $329.0 million, compared to $292.4 million in the prior year quarter. The increase in net revenue was primarily attributable to an increase in volumes across all lines of business, led by the West and Central regions. Net revenue grew organically by $9.3 million, or 3.2%, compared to the prior year quarter.

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Further Adjusted EBITDA increased 28.4% to $78.1 million, compared to $60.9 million in the prior year quarter, with growth in all regions. As a percentage of net revenue, Further Adjusted EBITDA improved to 23.8%, compared to 20.8% in the prior year quarter. Adjusted EBITDA by region in the second quarter 2015 compared to the prior year quarter was as follows:

Gross profit increased 25.1% to $115.8 million, compared to $92.5 million in the prior year quarter. As a percentage of net revenue, gross profit improved to 35.2%, compared to 31.6% in the prior year quarter, primarily attributable to a higher mix of net revenue from materials and products as a result of organic improvement and acquisition activity.

Materials Results – Net revenue from materials increased 29.6% to $88.1 million, compared to $67.9 million in the prior year quarter. Aggregates volumes grew 33.1% driven by 3.5% organic volume growth and the remainder attributable to acquisitions. Aggregates organic price increased 5.1% with the improvement due to higher prices across most markets. Including acquisitions, aggregates price increased 0.3% primarily due to the regional mix effect of acquisitions in markets with lower absolute prices, which partially offset organic price growth. Cement volume and price increased 0.7% and 9.1%, respectively, both driven by additional market demand. Gross profit from materials grew 34.7% to $52.7 million, compared to $39.1 million in the prior year quarter.

Products Results – Net revenue from products increased 12.9% to $173.2 million, compared to $153.4 million in the prior year quarter. Ready-mixed concrete volumes increased 17.5% primarily attributable to acquisitions. Ready-mixed concrete price increased 6.4%, largely benefitting from the pass through of higher cement industry prices. Asphalt volume and price increased 7.0% and 4.8% respectively, mostly reflecting stronger market demand. Gross profit from products increased 40.1% to $44.9 million, compared to $32.1 million in the prior year quarter.

Liquidity and Capital Resources

In April 2015, in connection with its initial public offering in March 2015, the Company redeemed $288.2 million aggregate principal amount of its outstanding 10 ¹⁄₂% Senior Notes due 2020 at a redemption price equal to par, plus an applicable premium of $38.2 million and $5.2 million of accrued and unpaid interest.

At June 27, 2015, the Company had cash of $12.6 million and total outstanding debt of $827.2 million, as compared to cash of $13.2 million and total outstanding debt of approximately $1,064.9 million at December 27, 2014. As of June 27, 2015, the Company’s borrowing capacity was $144.8 million on its $235.0 million revolving credit facility, excluding $24.2 million of letters of credit.

Subsequent Events

On July 17, 2015, Summit completed the acquisition of the Davenports Assets, including a 1.2 million short ton cement plant, a quarry and seven cement distribution terminals, from Lafarge for a purchase price of $450.0 million in cash and a cement distribution terminal in Bettendorf, Iowa. The Davenport Assets are being integrated with and will operate as Continental Cement Company, an existing wholly-owned subsidiary of Summit.

In connection with the acquisition, on July 8, 2015, the Company issued $350.0 million in aggregate principal amount of 6.125% Senior Notes due 2023 at 100.0% of their par value. Additionally, on July 17, 2015, the Company refinanced its term loan under its senior secured credit facilities, in which the Company entered into a new $650 million term loan facility due 2022, replacing the prior $422 million term loan due 2019. The refinancing also reduced the applicable margins used to calculate interest rates for term loans under the Company’s senior secured credit facilities to 3.25% from 3.50%.

The Company used the combined net proceeds from the issuance of the senior notes and the refinancing of the term loan to finance an initial $370.0 million cash purchase price for the Davenport Assets, to refinance its existing senior secured term loan facility, to redeem $183.0 million aggregate principal amount of its outstanding 10 ¹⁄₂% Senior Notes due 2020 and to pay related fees and expenses. The remaining $80.0 million of the purchase price for the Davenport Assets is due by December 31, 2015 and accrues interest at an annual rate of 7.5%, payable monthly.

Webcast and Conference Call Information

Summit will conduct a conference call at 4:30 p.m. Eastern Time (2:30 p.m. Mountain Time) on Monday, August 3, 2015 to review second quarter results, discuss recent events, and conduct a question-and-answer period. A webcast of the conference call and presentation slides to be referred to on the call 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.

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To participate in the telephone conference call:

To listen to a replay of the telephone conference call:

About Summit Materials

Summit Materials is a leading vertically integrated construction materials company that supplies aggregates, cement, ready-mixed concrete and asphalt in the United States and British Columbia, Canada. Summit is a geographically diverse, aggregates-based business of scale that offers customers a single-source provider of construction materials and related downstream products in the residential, nonresidential, and public infrastructure end markets. Summit has completed more than 35 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 rules of the SEC regulate the use in filings with the SEC of “non-GAAP financial measures,” such as Adjusted EBITDA, Further Adjusted EBITDA, gross profit, adjusted net loss per share, and free cash flow 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 Adjusted EBITDA, Further Adjusted EBITDA, gross profit, adjusted net loss per share, and free cash flow 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. Further Adjusted EBITDA is defined in our senior secured credit facilities and used to measure compliance with covenants, including interest coverage and debt incurrence, and is used to measure our debt incurrence and restricted payment capacity under the indenture governing our senior notes. Our use of the terms Adjusted EBITDA, Further Adjusted EBITDA, gross profit and adjusted net loss per share, may vary from the use of such terms by others and should not be considered as alternatives to 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 and Further Adjusted EBITDA 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 and Further 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; (iv) income tax payments we are required to make; and (v) any cash requirements for the replacement cost of assets being depreciated or amortized. Because of these limitations, we rely primarily on our U.S. GAAP results and use Adjusted EBITDA and Further Adjusted EBITDA only supplementally.

Adjusted EBITDA, Further Adjusted EBITDA, gross profit, adjusted net loss per share, and free cash flow reflect an additional way 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. However, non-GAAP financial measures should not be construed as being more important than other comparable U.S. GAAP financial measures and should be considered in conjunction with the U.S. GAAP measures. In addition, non-

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GAAP financial measures are not standardized; therefore, it may not be possible to compare such financial measures with other companies’ non-GAAP financial measures having the same or similar names. 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 tables attached to this press release.

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 timing, funding of, and expectations for our anticipated purchase of the Davenport Assets, 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 prospectus dated March 11, 2015, filed with the SEC on March 13, 2015. 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.

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Consolidated Statements of Operations

($ in thousands, except share and per share amounts)

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Consolidated Balance Sheets

($ in thousands, except share and per share amounts)

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Consolidated Statements of Cash Flows

($ in thousands, except per share amounts)

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Revenue Data by Region and Product

($ in thousands, except per share amounts)

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Volume and Price Statistics

(Units in thousands, except per share amounts)

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Reconciliations of Non-GAAP Financial Measures

($ in thousands, except per share amounts)

The tables below reconcile our net income (loss) to Adjusted EBITDA and present Adjusted EBITDA by segment for the three and six months ended June 27, 2015 and June 28, 2014.

The table below reconciles our net income per share to adjusted net income per share for the three and six months ended June 27, 2015.

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Reconciliations of Non-GAAP Financial Measures

($ in thousands, except per share amounts)

The table below reconciles the Summit Materials, Inc. net (loss) per share to net earnings (loss) per share attributable to member of Summit Materials, LLC, post-IPO for the three and six months ended June 27, 2015:

The following table reconciles operating income to gross profit for the three and six months ended June 27, 2015 and June 28, 2014.

The following table reconciles net cash used for operating activities to free cash flow for the three and six months ended June 27, 2015 and June 28, 2014.

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SUMMIT MATERIALS, INC. AND SUBSIDIARIES

Unaudited Reconciliations of Non-GAAP Financial Measures

($ in thousands, except per share amounts)

The following table presents a reconciliation of net income (loss) to Further Adjusted EBITDA for the three and six months ended June 27, 2015 and June 28, 2014.

Contact:

Investor Relations:

303-515-5159

Investorrelations@summit-materials.com

Media Contact:

303-515-5158

mediarelations@summit-materials.com

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