Bellevue, WA Accessory Structures: ADU Rules (2026)

Washington House Bill 1337 signed in 2023 (codified in RCW 36.70A.681) dramatically expanded accessory dwelling unit rights statewide. Bellevue adopted compliant local regulations through Land Use Code amendments to LUC 20.30 allowing up to 2 accessory dwelling units per single-family residential lot - any combination of attached ADU, detached ADU (DADU), or junior ADU (JADU). Maximum unit size is 1000 square feet (or larger if local code allows). Owner-occupancy requirements are prohibited under state law meaning ADUs can be rented while the primary residence is also rented. Additional off-street parking beyond primary residence cannot be required within 0.5 mile of major transit stops (which covers much of Bellevue near light rail and Metro transit). Short-term rental (under 30 days) of ADUs is regulated separately under Bellevue STR rules. Design standards including setbacks, height (typically 24-30 feet), and lot coverage still apply. Sewer and water connection fees apply. Building permits required through MyBuildingPermit.com. Impact fees may be reduced or waived for ADUs per state law.