ADU rules in Spokane, WA — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Under Washington HB 1110 (middle housing) and HB 1337 (ADU), Spokane must allow at least two ADUs per single-family lot. No owner-occupancy requirement, no ADU parking requirement within half-mile of transit. ADUs up to 1,000 sq ft permitted.
Washington House Bill 1337 (2023) mandated all GMA-planning cities including Spokane allow at least two accessory dwelling units on every single-family lot: either two detached, or one attached plus one detached. Spokane updated its zoning under SMC Title 17C to comply. ADUs up to 1,000 square feet are explicitly allowed, with some provisions for larger units. Owner-occupancy requirements are prohibited. Off-street parking cannot be required for ADUs within one-half mile of frequent transit. HB 1110 further expanded middle housing, requiring Spokane to allow duplexes, triplexes, and fourplexes on lots formerly zoned single-family, with at least 6 units permitted within a quarter-mile of major transit stops. Building permits, sewer/water connection fees, and WA State Building Code compliance still apply. Short-term rental use of ADUs may be restricted under separate STR rules.
Unpermitted ADU construction: stop-work order, fines, and mandatory permitting. Non-compliant zoning restrictions by city could trigger state enforcement.
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See how Spokane's adu rules rules stack up against other locations.
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