Washington Tiny House Standards Under State Building Code

Washington adopts IRC Appendix Q for tiny houses on permanent foundations (under 400 square feet) through chapter 51-51 WAC, providing relaxed ceiling height and loft standards. RCW 35.21.686 defines tiny houses with wheels as recreational vehicles regulated under federal HUD or ANSI A119.5 standards. RCW 35.21.684 and RCW 36.01.225 require cities and counties to allow tiny house communities and prohibit blanket bans on tiny houses with wheels in residential zones meeting certain conditions.

Local prohibitions on tiny houses meeting state standards are preempted and unenforceable in qualifying zones.