CORRECTING and REPLACING Cornerstone Building Brands 2020 Annual Meeting and Proxy Materials

Please replace the release dated May 15, 2020 with the following corrected version to include the Company telephone number in the Registration and Attending the Annual Meeting section.

The corrected release reads:

CORNERSTONE BUILDING BRANDS 2020 ANNUAL MEETING AND PROXY MATERIALS

Cornerstone Building Brands, Inc. (NYSE: CNR) (the “Company”), a leading provider of exterior building products, filed and mailed its Proxy Statement for its Annual Meeting of Stockholders (the “Proxy Statement”) to all of the Company’s stockholders on April 29, 2020.

It has come to the Company’s attention that a portion of its stockholders may have experienced a delay in the delivery of the Proxy Statement and related materials. As a result of such delay, the Company is setting forth below some key information with respect to the Company’s annual meeting, including procedures for voting your shares and attending the annual meeting. Please note that all proxy materials, including the Notice of Annual Meeting of Stockholders, our Proxy Statement and our Annual Report to Stockholders are available at www.proxydocs.com/CNR.

Annual Meeting Information

The Annual Meeting of Stockholders will be held virtually solely online via live webcast on Thursday, May 28, 2020 at 10:00 a.m. EDT at www.proxydocs.com/CNR.

Stockholders have a choice of voting over the Internet, at www.proxypush.com/CNR (registered stockholders only), by telephone using the number 1-844-927-1815, or by mail using a traditional proxy card. By granting a proxy, you authorize the persons named in the proxy to represent you and vote your shares at the Annual Meeting. Those persons will also be authorized to vote your shares to adjourn the Annual Meeting from time to time and to vote your shares at any adjournments or postponements of the Annual Meeting.

If you give a proxy on your proxy card, or by telephone or the Internet, you may revoke it at any time before it is exercised at the Annual Meeting by (1) delivering written notice of revocation to the Corporate Secretary of Cornerstone, (2) signing, dating and delivering to the Corporate Secretary of Cornerstone a later dated proxy at our principal executive offices, which are located at 5020 Weston Parkway, Suite 400, Cary, North Carolina 27513, or (3) virtually attending the Annual Meeting and voting online. Virtual attendance at the Annual Meeting will not, in itself, constitute revocation of a completed and delivered proxy.

Voting Your Shares

If you were a stockholder of record at the close of business on April 15, 2020, you may vote at the Annual Meeting, vote by proxy over the telephone, vote by proxy through the Internet or vote by proxy using the proxy card delivered to you.

Stockholder of Record: Shares Registered in Your Name

If, on April 15, 2020, your shares were registered directly in your name with the Company’s transfer agent, Computershare Trust Company, N.A., then you are a stockholder of record. As a stockholder of record, you may vote online during the Annual Meeting or vote by proxy using any of the methods noted above. Specific instructions for voting by each of these methods are included in the proxy card. If you have not received your proxy card, please contact the Company 1-866-419-0042. Whether or not you plan to register and attend the Annual Meeting, we urge you to fill out and return the proxy card or vote by proxy over the telephone or Internet to ensure your vote is counted.

Beneficial Owner: Shares Registered in the Name of a Broker or Bank

If, on April 15, 2020, your shares were held, not in your name, but rather in an account at a brokerage firm, bank or other similar organization, then you are the beneficial owner of shares held in “street name” and the proxy materials should have been forwarded to you by that organization. The organization holding your account is considered to be the stockholder of record for purposes of voting at the Annual Meeting. As a beneficial owner, you have the right to direct your broker, bank or other agent regarding how to vote the shares in your account. You are also invited to attend the Annual Meeting. However, since you are not the stockholder of record, you may not vote your shares at the Annual Meeting unless you request and obtain a valid proxy from your broker, bank or other agent. You must follow the instructions from your broker, bank or other agent. If you have not received your proxy materials, please contact your broker, bank or other agent.

Registration and Attending the Annual Meeting

To be admitted to the Annual Meeting’s live webcast, you must register in advance at www.proxydocs.com/CNR prior to the registration deadline of 5:00 p.m. Eastern Time on May 26, 2020. As part of the registration process, you must enter the control number provided in your proxy card. If you have not received your proxy card, please contact the Company at 1-866-419-0042 if you are a registered holder or your broker, bank or other agent if you hold your shares through a broker, bank or other agent. After completion of your registration, further instructions, including a unique link to access the Annual Meeting, will be emailed to you.

You are entitled to participate in the Annual Meeting only if you were a stockholder of record of the Company as of the close of business on the record date of April 15, 2020, or if you hold a valid proxy for the Annual Meeting.

About Cornerstone Building Brands

Cornerstone Building Brands is a leading manufacturer of exterior building products in North America. Headquartered in Cary, North Carolina, the Company serves residential and commercial customers across new construction and the repair & remodel markets. As the #1 manufacturer of windows, vinyl siding, insulated metal panels, metal roofing and wall systems and metal accessories, Cornerstone Building Brands combines a comprehensive portfolio of products with an expansive national footprint that includes approximately 20,000 employees at manufacturing, distribution and office locations throughout North America. For more information, visit us at www.cornerstonebuildingbrands.com.

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Investor Relations Tina Beskid 1-866-419-0042 [e-mail]