BMCH BMC Stock Holdings Inc

As previously disclosed, on December 14, 2020, BMC Stock Holdings, Inc., a Delaware corporation (“BMC”), took certain actions to preserve compensation-related corporate income tax deductions for BMC that might otherwise be disallowed through the operation of Sections 280G and 4999 of the Internal Revenue Code of 1986, as amended, in connection with completing the transactions contemplated by that certain Agreement and Plan of Merger, dated as of August 26, 2020 (the “Merger Agreement”), by and among BMC, Builders FirstSource, Inc., a Delaware corporation (“Builders FirstSource”), and Boston Merger Sub I Inc., a Delaware corporation and a direct, wholly owned subsidiary of Builders FirstSource. As a result of the appreciation in the BMC common stock share price since taking these actions, the compensation committee of the BMC board of directors determined that it was necessary to take certain additional actions to preserve such tax deductions. On December 27, 2020, the compensation committee of the BMC board of directors approved the accelerated vesting and settlement, as of December 28, 2020, of (i) 19,444 restricted stock units (“RSUs”) granted on September 26, 2018 to Mr. David E. Flitman, President and Chief Executive Officer of BMC, and (ii) 16,836 RSUs granted on February 28, 2019 to Mr. Flitman. All of these RSUs would have otherwise vested and settled in connection with the completion of the transactions contemplated by the Merger Agreement, which is expected to occur on or about January 1, 2021, subject to the satisfaction or waiver of certain conditions set forth in the Merger Agreement.

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Cautionary Notice Regarding Forward-Looking Statements

This report, in addition to historical information, contains “forward-looking statements” (as defined in the Private Securities Litigation Reform Act of 1995) regarding, among other things, future events or the future financial performance of BMC Stock Holdings, Inc. (“BMC”) and Builders FirstSource, Inc. (“Builders FirstSource”). Words such as “may,” “will,” “should,” “plans,” “estimates,” “predicts,” “potential,” “anticipate,” “expect,” “project,” “intend,” “believe,” or the negative of these terms, and words and terms of similar substance used in connection with any discussion of future plans, actions or events identify forward-looking statements. Any forward-looking statements involve risks and uncertainties that are difficult to predict or quantify, and such risks and uncertainties could cause actual events or results to differ materially from the events or results described in the forward-looking statements, including risks, or uncertainties related to the novel coronavirus disease 2019 (also known as “COVID-19”) pandemic and its impact on the business operations of BMC and Builders FirstSource and on local, national and global economies, the growth strategies of BMC and Builders FirstSource, fluctuations of commodity prices and prices of the products of BMC and Builders FirstSource as a result of national and international economic and other conditions, or the significant dependence of both companies’ revenues and operating results on, among other things, the state of the homebuilding industry and repair and remodeling activity, lumber prices and the economy. Neither BMC nor Builders FirstSource may succeed in addressing these and other risks or uncertainties.

Forward-looking statements relating to the proposed business combination between BMC and Builders FirstSource include, but are not limited to: statements about the benefits of the proposed business combination between BMC and Builders FirstSource, including future financial and operating results; the plans, objectives, expectations and intentions of BMC and Builders FirstSource; the expected timing of completion of the proposed business combination; and other statements relating to the proposed merger that are not historical facts. Forward-looking statements are based on information currently available to BMC and Builders FirstSource and involve estimates, expectations and projections. Investors are cautioned that all such forward-looking statements are subject to risks and uncertainties, and important factors could cause actual events or results to differ materially from those indicated by such forward-looking statements. With respect to the proposed business combination between BMC and Builders FirstSource, these factors could include, but are not limited to: the risk that a condition to closing of the business combination may not be satisfied, including as a result of the failure to obtain approval of stockholders of BMC and Builders FirstSource on the expected terms and schedule or at all; the length of time necessary to consummate the proposed business combination, which may be longer than anticipated for various reasons; the risk that the businesses will not be integrated successfully; the risk that the cost savings, synergies and growth from the proposed business combination may not be fully realized or may take longer to realize than expected; the assumptions on which the parties’ estimates of future results of the combined business have been based may prove to be incorrect in a number of material ways, which could result in an inability to realize the expected benefits of the proposed business combination or exposure to material liabilities; the diversion of management time on issues related to the business combination; the effect of future regulatory or legislative actions on the companies or the industries in which they operate; the risk that the credit ratings of the combined company may be different from what the parties expect; economic and foreign exchange rate volatility; changes in the general economic environment, or social or political conditions, that could affect the businesses; the potential effect of the announcement or consummation of the proposed business combination on relationships with customers, suppliers, competitors, lenders, landlords, management and other employees; the ability to attract new customers and retain existing

customers in the manner anticipated or at all; the ability to hire and retain key personnel; reliance on and integration of information technology systems; the risks associated with assumptions the parties make in connection with the parties’ critical accounting estimates and legal proceedings; certain restrictions during the pendency of the business combination that may affect the ability of BMC and Builders FirstSource to pursue certain business opportunities or strategic transactions; and the potential of international unrest, economic downturn or effects of anticipated tax rates, raw material costs or availability, benefit or retirement plan costs, or other regulatory compliance costs.

Additional information concerning other risk factors pertaining to BMC and Builders FirstSource is also contained in the parties’ respective most recently filed Annual Reports on Form 10-K, subsequent Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, and other information filed with the Securities and Exchange Commission (the “SEC”). Many of these risks and uncertainties are beyond BMC’s or Builders FirstSource’s ability to control or predict. Because of these risks and uncertainties, you should not place undue reliance on these forward-looking statements. It is not possible to anticipate or foresee all risks and uncertainties, and investors should not consider any list of risks and uncertainties to be exhaustive or complete. Furthermore, neither BMC nor Builders FirstSource undertakes any obligation to update publicly or revise any forward-looking statements to reflect events or circumstances that may arise after the date of this report. Nothing in this report is intended, or is to be construed, as a profit forecast or to be interpreted to mean that the earnings per share of the common stock of BMC or of the common stock of Builders FirstSource for the current or any future financial years, or the earnings per share of the common stock of the combined company, will necessarily match or exceed the historical published earnings per share of the common stock of BMC or Builders FirstSource, as applicable. Annualized, pro forma, projected and estimated numbers are used for illustrative purpose only, are not forecasts and may not reflect actual results. All subsequent written and oral forward-looking statements concerning BMC, Builders FirstSource, the proposed business combination, the combined company or other matters and attributable to BMC, Builders FirstSource or any person acting on their behalf are expressly qualified in their entirety by the cautionary statements above.