ADU rules by city in Washington

• ADU & backyard cottage rules in Tacoma, WA — What the engine reads for Tacoma lots: the UR-1, UR-2 and UR-3 zones from Home in Tacoma — coverage, height, setbacks and floor-area limits — and what they mean for a backyard cottage.
• ADU & backyard cottage rules in King County (unincorporated), WA — What the engine reads for unincorporated King County lots: the R-1 to R-48 zone dimensions from KCC 21A.12.030 — impervious surface, height, setbacks and density — and what they mean for an ADU.
• ADU & backyard cottage rules in Kent, WA — What the engine reads for Kent lots: the NR-L, NR-S, NR-2 and NR-3 zones from the 2025 ReCode — coverage, height, setbacks, the detached ADU setbacks and parking.
• ADU & backyard cottage rules in Mukilteo, WA — What the engine reads for Mukilteo lots: the RD zones from Ordinance 1516 (2025) — coverage, height, setbacks, detached ADU setbacks and the parking rule.
• ADU & backyard cottage rules in Auburn, WA — What the engine reads for Auburn lots: the RC and R-1 to R-3 zones after Ordinance 6959 — impervious limits, height, setbacks, the 300–1,000 sq ft ADU size range and parking.
• ADU & backyard cottage rules in Snohomish County (unincorporated), WA — What the engine reads for unincorporated Snohomish County lots: the R-9600, R-8400, R-7200 and R-5 zones — coverage, height, setbacks — and the 1,200 sq ft detached ADU cap.