UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of Earliest Event Reported): June 3, 2015

STOCK BUILDING SUPPLY HOLDINGS, INC.

(Exact name of registrant as specified in its charter)

8020 Arco Corporate Drive, Suite 400

Raleigh, North Carolina 27617

(Address of principal executive offices) (Zip Code)

(919) 431-1000

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

On June 3, 2015, Stock Building Supply Holdings, Inc., a Delaware corporation (the “Company”), and Building Materials Holding Corporation, a Delaware corporation (“BMC”), issued a joint press release announcing the execution of an Agreement and Plan of Merger (the “Merger Agreement”), dated June 2, 2015, between the Company and BMC. Pursuant to the Merger Agreement, subject to certain conditions, BMC will be merged with and into the Company, with the Company surviving the merger (the “Merger”). A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

In addition, on June 3, 2015, the Company provided supplemental information regarding the Merger in connection with a presentation to analysts and investors. A copy of the presentation is attached hereto as Exhibit 99.2 and incorporated herein by reference.

In accordance with General Instruction B.2 of Form 8-K, the information in this Item 7.01, including Exhibits 99.1 and 99.2, shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that section. The information in this Item 7.01 shall not be incorporated by reference into any filing or other document pursuant to the Securities Act of 1933, as amended, except as shall be expressly set forth by specific reference in such filing or document.

FORWARD-LOOKING STATEMENTS

This document contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements are typically identified by words or phrases such as “may,” “might,” “predict,” “future,” “seek to,” “assume,” “goal,” “objective,” “continue,” “will,” “could,” “should,” “would,” “anticipate,” “estimate,” “expect,” “project,” “intend,” “plan,” “believe,” “target,” “prospects,” “potential” and “forecast,” or the negative of such terms and other words, terms and phrases of similar meaning. Forward-looking statements involve estimates, expectations, projections, goals, forecasts, assumptions, risks and uncertainties. The Company cautions readers that any forward-looking statement is not a guarantee of future performance and that actual results could differ materially from those contained in the forward-looking statement. Such forward-looking statements include, but are not limited to, statements about the benefits of the Merger involving BMC and the Company, including future financial and operating results, the Company’s or BMC’s plans, objectives, expectations and intentions, the expected timing of completion of the transaction, and other statements that are not historical facts. There are a number of risks and uncertainties that could cause actual results to differ materially from the forward-looking statements included in this communication. Important factors that could cause actual results to differ materially from those indicated by such forward-looking statements include risks and uncertainties relating to: the ability to obtain the requisite BMC and the Company shareholder approvals; the risk that the Company or BMC may be unable to obtain governmental and regulatory approvals required for the Merger, or required governmental and regulatory approvals may delay the Merger or result in the imposition of conditions that could cause the parties to abandon the Merger; the risk that a condition to closing of the Merger may not be satisfied; the timing to consummate the Merger; the risk that the businesses will not be integrated successfully; the risk that the cost savings and any other synergies from the transaction may not be fully realized or may take longer to realize than expected; disruption from the transaction making it more difficult to maintain relationships with customers, employees or suppliers; the diversion of management time on Merger-related issues; general worldwide economic conditions and related uncertainties; the effect of changes in governmental regulations; and other factors discussed or referred to in the “Risk Factors” section of the Company’s most recent Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 2, 2015, and our subsequent filings with the SEC. These risk factors, as well as other risks associated with the Merger, will be more fully discussed in the Registration Statement and the Proxy /Consent Solicitation Statement/Prospectus (as defined below). All such factors are difficult to predict and are beyond the Company and BMC’s control. All forward-looking statements attributable to the Company or persons acting on the Company’s behalf are expressly qualified in their entirety by the foregoing cautionary statements. All such statements speak only as of the date made, and the Company and BMC undertake no obligation to update or revise publicly any forward-looking statements, whether as a result of new information, future events or otherwise.

NO OFFER OR SOLICITATION

The information in this communication is for informational purposes only and is neither an offer to purchase, nor a solicitation of an offer to sell, subscribe for or buy any securities or the solicitation of any vote or approval in any jurisdiction pursuant to or in connection with the proposed transactions or otherwise, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of applicable law. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended, and otherwise in accordance with applicable law.

ADDITIONAL INFORMATION AND WHERE TO FIND IT

The proposed transaction involving the Company and BMC will be submitted to the respective stockholders of the Company and BMC for their consideration. In connection with the Merger and special meeting of the Company’s stockholders, the Company expects to file with the SEC a registration statement on Form S-4 (the “Registration Statement”) that will include a proxy statement/consent solicitation/prospectus (the “Proxy/Consent Solicitation Statement/Prospectus”). The definitive Registration Statement and the Proxy/Consent Solicitation Statement/Prospectus will contain important information about the Merger, the Merger Agreement and related matters. This communication may be deemed to be solicitation material in respect of the proposed transaction between BMC and the Company. This communication is not a substitute for the Registration Statement, Proxy/Consent Solicitation/Prospectus or any other documents that the Company or BMC may file with the SEC or send to shareholders in connection with the proposed transaction. INVESTORS AND SECURITY HOLDERS OF THE COMPANY AND BMC ARE URGED AND ADVISED TO READ THE REGISTRATION STATEMENT AND THE PROXY/CONSENT SOLICITATION STATEMENT/PROSPECTUS CAREFULLY WHEN THEY BECOME AVAILABLE, AS WELL AS ANY OTHER RELEVANT DOCUMENTS FILED WITH THE SEC AND ANY AMENDMENTS OR SUPPLEMENTS TO THOSE DOCUMENTS, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION. The Registration Statement, the Proxy /Consent Solicitation Statement/Prospectus and any other documents filed or furnished by the Company with the SEC may be obtained free of charge at the SEC’s website (www.sec.gov). The Registration Statement, the Proxy/Consent Solicitation Statement/Prospectus and other relevant documents will also be available to security holders, without charge, from the Company by going to its investor relations page on its corporate website at http://ir.stocksupply.com or from BMC by directing a request to Paul Street, Corporate Secretary of BMC, via email or telephone (paul.street@buildwithbmc.com, (208) 331-4300.

PARTICIPANTS IN THE SOLICITATION

The Company, BMC, their respective directors and certain of their executive officers and employees may be deemed to be participants in the solicitation of proxies in connection with the proposed transaction. Information about the directors and executive officers of the Company is set forth in the proxy statement for the Company’s 2015 Annual Meeting of Stockholders, which was filed with the SEC on April 30, 2015. Information about the directors and executive officers of BMC and more detailed information regarding the identity of all potential participants, and their direct and indirect interests, by security holdings or otherwise, will be set forth in the Registration Statement and the Proxy/Consent Solicitation Statement/Prospectus. Investors may obtain additional information regarding the interests of such participants by reading the Registration Statement and the Proxy/Consent Solicitation Statement/Prospectus when they become available. You may obtain a free copy of the proxy statement for the Company’s 2015 Annual Meeting of Stockholders by going to its investor relations page on its corporate website at http://ir.stocksupply.com. You may obtain free copies of the Registration Statement, the Proxy/Consent Solicitation Statement/Prospectus and other relevant documents as described in the preceding paragraph.

(d) Exhibits.

SIGNATURE

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 undersigned hereunto duly authorized.

Date: June 3, 2015

EXHIBIT INDEX