Results of Operations and Financial Condition. On October 26, 2026 , Simpson Manufacturing Co., Inc. (the "Company") issued a press release announcing financial results for the quarter ended September 30, 2026, a copy of which is attached hereto as Exhibit 99.1 and is incorporated herein by this reference. This information is furnished pursuant to

Regulation FD Disclosures. On October 26, 2026 , the Company also issued a press release announcing that its Board of Directors has authorized a new share repurchase program permitting the Company to purchase up to $1.0 billion of its outstanding common shares, with no expiration date for the program. This authorization supersedes the prior $200 million authorization. The Company may repurchase shares from time to time in the open market or in other privately negotiated transactions, subject…

and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

Results of Operations and Financial Condition. On February 9, 2026 , Simpson Manufacturing Co., Inc. issued a press release announcing financial results for the fourth quarter and full year ended December 31, 2025, a copy of which is attached hereto as Exhibit 99.1 and is incorporated herein by this reference. This information is furnished pursuant to

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant The information set forth under

Entry into a Material Definitive Agreement On December 16, 2025, Simpson Manufacturing Co., Inc. (the “Company”) entered into that certain Second Amended and Restated Credit Agreement (the “Second Amended and Restated Credit Agreement”), among the Company, the subsidiaries of the Company party thereto as guarantors, the lenders party thereto, Wells Fargo Bank, National Association (“Wells Fargo”), as administrative agent, and the other parties party thereto. The Second Amended and Restated Cr…

and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

Results of Operations and Financial Condition. On February 10, 2025 , Simpson Manufacturing Co., Inc. issued a press release announcing financial results for the fourth quarter and full year ended December 31, 2024, a copy of which is attached hereto as Exhibit 99.1 and is incorporated herein by this reference. This information is furnished pursuant to

Director — Angela Drake: The filing discloses the appointment of a new independent director to the board, which is a routine governance event and not a departure of a senior executive.

CFO — Brian Magstadt: The CFO is retiring with a named internal successor and a transition period as an advisor, representing an orderly succession rather than a sudden loss of leadership.

and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

CFO — Brian Magstadt: The CFO is retiring with a defined effective date and the company is conducting a search for a successor, indicating an orderly succession rather than a sudden loss.

and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

Executive Vice President — Roger Dankel: The Executive Vice President is retiring in an orderly transition to an advisor role, which constitutes a planned succession rather than a sudden loss of a senior executive.

and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

Results of Operations and Financial Condition. On February 5, 2024 , Simpson Manufacturing Co., Inc. issued a press release announcing financial results for the fourth quarter and full year ended December 31, 2023, a copy of which is attached hereto as Exhibit 99.1 and is incorporated herein by this reference. This information is furnished pursuant to

and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

Other Events. On October 10, 2023, Simpson Manufacturing Co., Inc. (the “Company”) announced that it had experienced disruptions in its Information Technology (IT) infrastructure and applications resulting from a cybersecurity incident. The Company identified unauthorized activity on some of its IT systems and took immediate steps to stop and remediate the activity, including taking certain systems offline and engaging leading third-party cybersecurity experts to assist with remediation and i…

Senior Vice President of Finance — Kevin Swartzendruber: The filing discloses a planned retirement of a senior finance officer with no indication of a sudden loss or disagreement, representing an orderly succession rather than a shock departure.

Other Events. On October 10, 2023, Simpson Manufacturing Co., Inc. (the “Company”) experienced disruptions in its Information Technology (IT) infrastructure and applications resulting from a cybersecurity incident. After becoming aware of the malicious activity, the Company began taking steps to stop and remediate the activity, including taking certain systems offline. The Company is working diligently to respond to and address this issue. The incident has caused, and is expected to continue…

and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

Director — Chau Banks, Felica Coney: The filing discloses the appointment of two new independent directors to the board, which is a standard governance action and not a departure of an executive officer.