Simpson Manufacturing Co., Inc.

(a) The following documents are filed as part of this Annual Report on Form 10-K:

1. Consolidated financial statements

The following consolidated financial statements are filed as a part of this report:

Reports of Independent Registered Public Accounting Firms

Consolidated Statements of Earnings and Comprehensive Income for the years ended December 31, 2025, 2024 and 2023

Consolidated Statements of Stockholders’ Equity for the years ended December 31, 2025, 2024 and 2023

Notes to Consolidated Financial Statements

2. Financial Statement Schedules

The following consolidated financial statement schedule for each of the years in the three-year period ended December 31, 2025, is filed as part of this Annual Report on Form 10-K:

Schedule II - Valuation and Qualifying Accounts-Years ended December 31, 2025, 2024 and 2023.

All other schedules have been omitted as the required information is not present or is not present in amounts sufficient to require submission of the schedule, or because the information required is included in the consolidated financial statements and related notes thereto.

(b) Exhibits

The following exhibits are either incorporated by reference into, or filed or furnished with, this Annual Report on Form 10-K, as indicated below.

3.1 Certificate of Incorporation of Simpson Manufacturing Co., Inc., as amended, is incorporated by reference to Exhibit 3.1 of its Quarterly Report on Form 10-Q for the quarter ended March 31, 2018.

3.2 Certificate of Amendment of Certificate of Incorporation of Simpson Manufacturing Co., Inc.is incorporated by reference to Exhibit 3.1 of the Company's Current Report on Form 8-K filed on May 6, 2024.

3.3 Amended and Restated Bylaws of Simpson Manufacturing Co., Inc., as amended, are incorporated by reference to Exhibit 3.1 of the Company's Current Report on Form 8-K filed on March 14, 2023.

4.1 Description of Securities Registered under Section 12 of the Exchange Act is incorporated by reference to Exhibit 4.1 of the Company's Annual Report on Form 10-K for the year ended December 31, 2024.

10.1*Form of Indemnification Agreement between Simpson Manufacturing Co., Inc. and its directors and executive officers, as well as the officers of Simpson Strong-Tie Company Inc., is incorporated by reference to Exhibit 10.2 of Simpson Manufacturing Co., Inc.’s Annual Report on Form 10-K for the year ended December 31, 2004.

10.2 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, as administrative agent, and the other parties party thereto is incorporated by reference to Exhibit 10.1 of the Company's Current Report on Form 8-K filed April 4, 2022.

10.3 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, as administrative agent, and the other parties party thereto is incorp orated by reference to Exhibit 10.1 of the Company's Current Report on Form 8-K filed December 22, 2025.

10.4*Simpson Manufacturing Co., Inc. Executive Officer Cash Profit Sharing Plan, as amended through March 17, 2017 is incorporated by reference to Exhibit 10.5 of its Annual Report on Form 10-K dated February 28, 2024.

10.5*Simpson Manufacturing Co., Inc. Amended and Restated 2011 Incentive Plan is incorporated by reference to Exhibit A of Simpson Manufacturing Co., Inc.’s Schedule 14A Proxy Statement dated March 9, 2015.

10.6*Simpson Manufacturing Co., Inc. 401(k) Profit Sharing Plan is incorporated by reference to Exhibit 4.5 of Simpson Manufacturing Co., Inc.’s Registration Statement on Form S-8, File Number 333-173811, dated December 15, 2015.

10.7*Simpson Manufacturing Co., Inc. Executive Severance Plan is incorporated by reference to Exhibit 10.1 of the Company's Current Report on Form 8-K filed on May 6, 2024.

10.8*Simpson Manufacturing Co., Inc. Non-qualified Plan is incorporated by reference to Exhibit 4.3 of the Company's Form S-8 filed on May 8, 2023.

10.9*Form of Simpson Manufacturing Co., Inc. Director Time Based Restricted Stock Unit Agreement is incorporated by reference to Exhibit 10.9 of its Annual Report on Form 10-K dated February 28, 2022.

10.10*Form of Simpson Manufacturing Co., Inc. 2024 Performance Based Restricted Stock Unit Agreement is incorporated by reference to Exhibit 10.12 of its Annual Report on Form 10-K dated February 28, 2024.

10.11*Form of Simpson Manufacturing Co., Inc. 2024 Time Based Restricted Stock Unit Agreement is incorporated by reference to Exhibit 10.13 of its Annual Report on Form 10-K dated February 28, 2024.

10.12*Form of Simpson Manufacturing Co., Inc. 2026 Performance Based Restricted Stock Unit Agreement isfiled herewith.

10.13*Form of Simpson Manufacturing Co., Inc. 2026 Time Based Restricted Stock Unit Agreement isfiled herewith.

19.1 Insider Trading Policy of Simpson Manufacturing Co., Inc., effective as of February 20, 2025, isincorporated by reference to Exhibit 19.1 of its Annual Report on Form 10-K dated March 3, 2025.

21 List of Subsidiaries of the Registrant is filed herewith.

23 Consent of Grant Thornton LLP is filed herewith.

31.1 Chief Executive Officer’s Rule 13a-14(a)/15d-14(a) Certification is filed herewith.

31.2 Chief Financial Officer’s Rule 13a-14(a)/15d-14(a) Certification is filed herewith.

32. Section 1350 Certifications are furnished herewith.

97 Compensation Recovery Policy of Simpson Manufacturing Co., Inc., effective as of July 28, 2023, is incorporated by reference to Exhibit 97 of its Annual Report on Form 10-K dated February 28, 2024.

101 Financial statements from the annual report on Form 10-K of Simpson Manufacturing Co., Inc. for the year ended December 31, 2025, formatted in XBRL, are filed herewith and include: (i) the Consolidated Balance Sheets, (ii) the Consolidated Statements of Operations, (iii) the Consolidated Statement of Earnings and Comprehensive Income, (iv) the Consolidated Statements of Stockholders’ Equity, (v) the Consolidated Statements of Cash Flows and (vi) the Notes to Consolidated Financial Statements.

104 Cover Page Interactive Data File (embedded within the Inline XBRL document).