You must make sure the overhead supporting members are designed, based upon impact loads, with a safety factor of:
Wash. Admin. Code § 296-56-60205
Statutory Authority: RCW 49.17.040 and 49.17.050. 86-03-064 (Order 86-02), § 296-56-60205, filed 1/17/86; 85-01-022 (Order 84-24), § 296-56-60205, filed 12/11/84.