Washington Revised Code Title 36. Counties § 36.01.227. County may not limit number of unrelated persons occupying a household or dwelling unit--Exceptions

Except for occupant limits on group living arrangements regulated under state law or on short-term rentals as defined in RCW 64.37.010 and any lawful limits on occupant load per square foot or generally applicable health and safety provisions as established by applicable building code or county ordinance, a county may not regulate or limit the number of unrelated persons that may occupy a household or dwelling unit.