Renton, WA Accessory Structures: Tiny Homes (2026)

Washington State allows tiny homes on foundations as permanent dwellings or ADUs under the International Residential Code Appendix Q (adopted statewide under RCW 19.27). In Renton, a tiny home on a permanent foundation can be a primary dwelling, a detached ADU, or a cottage in certain cottage housing developments under RMC 4-2-115 and RMC 4-9-240 (cottage housing provisions). Units must meet minimum room size, ceiling height (6 feet 8 inches in main living area per Appendix Q), egress window, smoke and CO alarm, and insulation requirements. Tiny homes used as ADUs benefit from WA HB 1337 — two allowed per lot, no owner-occupancy requirement, no parking within one-half mile of transit, and expedited permitting. Tiny houses on wheels (THOW) are classified as either RVs under RCW 46.04 (if trailer certified) or Park Model RVs — they cannot be used as permanent residences in Renton residential zones under RMC 4-2-080. Temporary occupancy of an RV while building a primary residence requires a temporary placement permit and a time limit. Tiny home villages for homelessness under RCW 35.21.683 and RCW 36.01.290 have specific siting rules and are allowed in certain zones with a conditional use permit. Manufactured tiny homes meeting HUD code are treated like manufactured homes under RMC 4-2-115.