Showing ordinances that apply to Mirrormont, WA
Mirrormont is an unincorporated community (population 3,858) in King County, Washington. Because Mirrormont is not an incorporated city, it does not have its own municipal code. Instead, King County ordinances apply directly to properties here. The tiny homes rules below are the ones that govern your area.
Unincorporated King County allows tiny homes on foundations that meet the Washington State Building Code (RCW 19.27 / 2021 IRC Appendix Q). Tiny houses on wheels are treated as RVs and limited under KCC Title 21A zoning.
Tiny homes in unincorporated King County are regulated under Title 16 (Building and Construction) and Title 21A (Zoning) of the King County Code, combined with the Washington State Building Code (RCW 19.27) and the 2021 International Residential Code including Appendix Q for Tiny Houses. A permanent tiny home built on a foundation of 400 square feet or less qualifies under IRC Appendix Q, which relaxes ceiling height, loft, and stair requirements. The home must still meet state energy code, plumbing code, and electrical code. In most residential zones (R-1 through R-8), a tiny home may serve as a primary dwelling if it meets minimum dwelling unit standards, or as an accessory dwelling unit (ADU) under King County ADU rules allowing one attached and one detached ADU per single-family lot. Washington HB 1337 (2023) requires GMA-planning jurisdictions to allow at least 2 ADUs per lot by right, which King County has implemented. Tiny houses on wheels (THOWs) are classified as recreational vehicles under Washington law and may not be used as permanent dwellings on residential lots unless placed in a licensed RV park or manufactured/mobile home park. Temporary occupancy of a THOW during active construction of a primary residence is sometimes permitted with a temporary use permit. Critical areas including wetlands, streams, steep slopes, and salmon habitat (KCC 21A.24) impose additional siting restrictions. Septic systems must be approved by Seattle-King County Public Health under KCC Title 13.
Tiny homes built without permits or occupied as THOWs in residential zones trigger code enforcement under KCC Title 23, with civil penalties starting at 100 dollars per day, stop-work orders, and required removal or legalization. Critical area violations carry penalties up to 5,000 dollars per day.
See how Mirrormont's tiny homes rules stack up against other locations.
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