Section 1 – Conflict Minerals Disclosure

Item 1.01 Conflict Minerals Disclosure and Report

Background

Builders FirstSource, Inc., a Delaware
corporation formed in 1998, is a leading supplier of building materials, manufactured components and construction services to professional contractors,

sub-contractors,

and consumers. In this specialized
disclosure report, references to the “company,” “we,” “our,” “ours” or “us” refer to Builders FirstSource, Inc. and its consolidated subsidiaries.

Rule

13p-1

(the “Rule”) promulgated under the Securities Exchange Act of 1934, as amended, requires public
disclosure of certain information when a company manufactures or contracts to manufacture products that include cassiterite, columbite-tantalite, gold, wolframite, and their derivatives, which are limited to tin, tantalum or tungsten (collectively,
the “Conflict Minerals”), that are necessary to the functionality or production of such products. For purposes of the Rule, the “Covered Countries” are the Democratic Republic of the Congo or any of its adjoining countries,
which, for the period covered by this report, are the Republic of Congo, the Central African Republic, South Sudan, Uganda, Rwanda, Burundi, Tanzania, Zambia and Angola.

Conflict Minerals Disclosure

While we are primarily a
distributor and reseller of products manufactured by others, we do manufacture certain products, including without limitation trusses, wall panels, stairs, specialty millwork, windows and

pre-hung

doors. Some
of these products utilize fasteners, hardware or other components that may contain Conflict Minerals.

During 2021 we undertook a comprehensive review of
the products that we manufacture or contract to have manufactured. This review included an analysis of all of the components utilized in these products to determine (i) which products may contain Conflict Minerals and (ii) the
identification of all suppliers from whom we source components that may contain Conflict Minerals. Our senior manufacturing personnel and internal legal counsel were involved with this analysis and approved the scope of the analysis as well as the
reasonable country of origin inquiry described below. Based upon this internal review, we determined that certain components utilized in our manufacturing processes or incorporated into our manufactured or contracted to manufacture products likely
contained Conflict Minerals that were necessary to the functionality or production of such products.

As a result of this comprehensive product review, we
initiated a good faith reasonable country of origin inquiry as required by the Rule. Our inquiry was designed to determine whether any of the Conflict Minerals that were necessary to the functionality or production of our manufactured or contracted
to manufacture products during the 2021 calendar year originated in any of the Covered Countries and whether any of the Conflict Minerals were from recycled or scrap sources. We adopted the Conflict Minerals reporting template established by the
Conflict-Free Sourcing Initiative and sent this template to all suppliers that we identified as potentially supplying us with Conflict Minerals for our manufactured or contracted to manufacture products. All of these suppliers were asked to complete
the Conflict Minerals reporting template established by the Conflict-Free Sourcing Initiative and to disclose whether Conflict Minerals were present in the products we purchased from them and, if so, the country of origin of the Conflict Minerals.

We received responses from suppliers that accounted for substantially all of the total components we
purchased in 2021 that we determined likely contained Conflict Minerals that were necessary to the functionality or production of products we manufacture or contract to manufacture. We also followed up with those suppliers that failed to timely
complete the reporting template or that provided incomplete or inconsistent responses.

All but one of our responding suppliers reported that Conflict
Minerals either were not present in the components supplied to us or that the Conflict Minerals contained in such components did not or were not known to originate in any of the Covered Countries. However, it is not clear from that one
supplier’s response, whether the Conflict Minerals contained in the components supplied to us by this supplier actually originated from such smelters or the Covered Countries. Based on the response from this supplier, we were unable to
determine with certainty that all Conflict Minerals that were necessary to the functionality or production of our manufactured or contracted to manufacture products did not originate in any of the Covered Countries.

Pursuant to the Public Statement issued by the SEC’s Division of Corporation Finance on April 7, 2017, we have only provided the disclosure required
under the provisions of paragraphs (a) and (b) of Item 1.01 of Form SD.

This information and our Responsible Supply Chain Policy are publicly
available at

www.bldr.com

.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the duly
authorized undersigned.

Dated: May 27, 2022