Wash. Admin. Code § 51-51-0702
R702.5 Other finishes. Wood veneer paneling and hard-board paneling shall be placed on wood or cold-formed steel framing spaced not more than 16 inches (406 mm) on center. Wood veneer and hardboard paneling less than 1/4-inch (6 mm) nominal thickness shall not have less than a 3/8-inch (10 mm) gypsum board or gypsum panel product backer. Wood veneer paneling not less than 1/4-inch (6 mm) nominal thickness shall conform to ANSI/HPVA HP-1. Hardboard paneling shall conform to CPA/ANSI A135.5. All structural panel components within the conditioned space such as plywood, particle board, wafer board and oriented strand board shall be identified as "EXPOSURE 1," "EXTERIOR" or "HUD-APPROVED."
Wash. Admin. Code § 51-51-0702
Statutory Authority: RCW 19.27.031 and 19.27.074. 10-03-098, § 51-51-0702, filed 1/20/10, effective 7/1/10.