ADU rules in Spokane County, WA — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Spokane County allows one accessory dwelling unit (ADU) per single-family lot. Detached ADUs are capped at 800 sq ft on the ground floor and 2 bedrooms, on lots of at least 10,000 sq ft. Attached ADUs are capped at 900 sq ft.
Under Spokane County Zoning Code Chapter 14.606 (LDR, LDR-P, MDR, HDR zones), a detached ADU may contain no more than 2 bedrooms and measure no more than 800 sq ft on the main (ground) floor, needs a pitched roof (min 4:12 slope, ridge under 24 ft), and is not allowed on lots under 10,000 sq ft. An attached ADU must not exceed 35% of the building's livable floor area nor 900 sq ft, whichever is less, and must keep the single-family appearance. Only one ADU is allowed per lot, and it can't be combined with a duplex or multi-family use. One extra off-street parking space is required. Detached ADUs are a conditional use requiring Hearing Examiner review.
ADUs built without required conditional-use approval or building permits are zoning-code violations enforced by Spokane County Building and Planning; correction or removal may be ordered.
Other ordinances people look up for this city. Green dot = verified primary-source excerpt.
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