Exhibit 21

Simpson Manufacturing Co., Inc. and Subsidiaries

List of Subsidiaries of Simpson Manufacturing Co., Inc.

At February 28, 2011

1.Simpson Strong-Tie Company Inc., a California corporation

2.Simpson Strong-Tie International, Inc., a California corporation

3.Simpson Strong-Tie Canada, Limited, a Canadian corporation

4.Simpson Strong-Tie Europe EURL, a French corporation

5.Simpson Strong-Tie, S.A.S., a French corporation

6.Simpson Strong-Tie Japan, Inc., a California corporation

7.Simpson Strong-Tie Australia, Inc., a California corporation

8.Simpson Strong-Tie A/S, a Danish corporation

9.Simpson Strong-Tie GmbH, a German corporation

10.Simpson Strong-Tie Sp.z,o.o., a Polish corporation

11.Simpson France SCI, a French corporation

12.Simpson Strong-Tie Australia Pty Limited, an Australian corporation

13.Simpson Strong-Tie Mexico, S. de R.L. de C.V., a Mexican corporation

14.Simpson Strong-Tie Asia Limited, a Hong Kong company

15.Simpson Strong-Tie Asia Holding Limited, a Hong Kong company

16.Simpson Strong-Tie (Beijing) Company Limited, a Chinese company

17.Simpson Strong-Tie (Zhangjiagang) Co., Ltd., a Chinese company

18.Simpson Strong-Tie Ireland Limited, an Irish company

19.Ahorn-Geräte & Werkzeuge Vertriebs GmbH, a German company

20.Simpson Strong-Tie s.r.o., a Czech company

21.Societe Civile Immobiliere IMAG SCI, a French corporation

22.Socom S.A.S., a French corporation