Spokane's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Spokane, Washington, there are 9 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

Tiny Homes

Tiny homes on foundations can qualify as ADUs under HB 1337 in Spokane. Tiny homes on wheels (THOW) are regulated as RVs and generally cannot be permanent dwellings outside designated parks. Minimum 70 sq ft per WA code.

Key details: Foundation Tiny: ADU-eligible under HB 1337. THOW: Treated as RV. Min Room: 70 sq ft per WA code. RV Parking Limit: 14-30 days typical. Factory-Built: WAC 296-150F certified.

Unpermitted THOW as residence: code enforcement action, requirement to move or remove. Foundation tiny home without permits: retroactive permitting and potential removal.

Carport Rules

Carports in Spokane require building permits and must meet setbacks, height, and lot coverage limits under SMC Title 17C. Front-yard carports generally prohibited in residential zones. Structural attachment rules apply.

Key details: Permit: Required. Snow Load: ~39 psf ground. Setbacks: 5 ft side/rear typical. Front Yard: Generally prohibited. Historic Districts: Design review applies.

Unpermitted carports: stop-work, permit-after-the-fact fees, or removal if non-compliant. Encroachment into setbacks: removal or variance application.

ADU Permits

Spokane processes ADU permits ministerially under Spokane Municipal Code Chapter 17C.300, updated in 2024-2025 to comply with Washington HB 1337 (RCW 36.70A.680 et seq.). Two ADUs are allowed per lot in RA, R1, R2, RMF, and RHD zones. Applications go through the Permit Center at City Hall.

Key details: Code Chapter: SMC 17C.300. Review Type: Ministerial (no hearing). ADUs Per Lot: Up to 2 (HB 1337). Max Floor Area: 1,000 sq ft each (SMC 17C.300.110). Allowed Zones: RA, R1, R2, RMF, RHD.

Building an ADU without permits violates SMC Chapter 17F.040 (Building Code) and SMC 17C.300. Spokane Code Enforcement can issue stop-work orders, Notice and Order to Correct, and civil penalties under SMC 1.05 (typically starting around $100-$500 per violation). Unpermitted ADUs block sale, refinancing, and may trigger an order to remove the structure.

If you are coming from a city with tighter rules, you will find Spokane gives residents more flexibility on adu permits.

ADU Owner Occupancy

Under Washington HB 1337 (RCW 36.70A.696) and SMC 17C.300.110, Spokane does NOT require owner-occupancy for standard ADUs. A narrow exception applies when both an ADU and a short-term rental exist on the same lot - in that case one unit must be owner-occupied six months per year, effective July 11, 2025.

Key details: Standard ADU: No owner-occupancy required. Combined ADU+STR Rule: 6 months owner-occupancy (post-7/11/2025). State Authority: RCW 36.70A.696. Code Section: SMC 17C.300.110. Deed Restriction: None required for standard ADU.

There is no penalty for non-owner-occupancy of a standard ADU. Violating the combined ADU+STR owner-occupancy requirement effective July 11, 2025 triggers SMC 17C.300.110 enforcement: code enforcement may require the owner to re-occupy, remove the ADU, or cease STR operation. Failure to comply may result in revocation of the STR permit under SMC 17C.316.040 and civil penalties under SMC 1.05.

The rules around adu owner occupancy in Spokane lean permissive, but that does not mean anything goes.

ADU Impact Fees

Under Washington HB 1337 (RCW 36.70A.681), Spokane cannot charge impact fees on ADUs under 1,000 sq ft and is capped at 50% of single-family rates for larger ADUs. Spokane has not adopted general school or park impact fees - only its Transportation Impact Fee under SMC 17D.075 applies, and even that is reduced or waived for ADUs.

Key details: Authority: HB 1337 / RCW 36.70A.681. Under 1,000 sq ft: No impact fees. 1,000+ sq ft: Capped at 50% of SF rate. Spokane Impact Fee: Transportation only (SMC 17D.075). Permit Fees: ~$2,500-$6,000 typical.

Spokane cannot legally charge impact fees in excess of the HB 1337 caps. If overcharged, the homeowner may protest under RCW 82.02.070-.080 within 60 days of payment, or seek a writ of certiorari. Failure to pay required water/sewer capacity charges blocks permit issuance and final inspection; unpaid fees become a lien on the property.

The rules around adu impact fees in Spokane lean permissive, but that does not mean anything goes.

ADU Rental Restrictions

Spokane allows long-term rental (30+ days) of any ADU without restriction. Short-term rental of an ADU is allowed under SMC 17C.316.040 but only if the operator obtains an STR permit and city business license. Combined ADU+STR use on the same lot triggers a 6-month owner-occupancy rule under SMC 17C.300.110 (effective July 11, 2025).

Key details: Long-Term Rental: Unrestricted (HB 1337). STR Permit Required: Yes (SMC 17C.316.040). Combined ADU+STR Rule: 6 months owner-occupancy. Rent Control: Prohibited by RCW 35.21.830. Just-Cause Eviction: SMC Chapter 10.27.

Operating an unlicensed STR violates SMC 17C.316.040 with civil penalties under SMC 1.05 starting at $250 per violation per day. The Spokane Code Enforcement Office actively monitors Airbnb/VRBO listings tied to Spokane addresses. Failure to remit lodging taxes is referred to the Washington Department of Revenue. Combined ADU+STR violations of the SMC 17C.300.110 owner-occupancy rule may result in STR permit revocation.

Garage Conversions

Garage conversions to living space are allowed in Spokane under HB 1337 ADU rules. Require building permits for framing, electrical, plumbing, insulation, egress windows, and WA State Energy Code compliance.

Key details: Allowed: Yes under HB 1337. Permits: Full set required. Energy Code: R-38 ceiling, R-21 walls. Parking: Replacement may be waived. Egress: Code-compliant windows.

Unpermitted conversions: stop-work orders, retroactive permit fees, and possible reversal if non-compliant. Selling a home with unpermitted conversion can trigger disclosure issues.

Shed Rules

Sheds under 200 sq ft in Spokane are exempt from building permits per WA State Building Code and IRC R105.2. Setbacks still apply: typically 5 feet from side and rear property lines in residential zones.

Key details: Permit Exempt: Under 200 sq ft. Setbacks: Typically 5 ft sides/rear. Max Height: ~15 ft residential. Electrical: Permit always required. Floodplain: FEMA elevation applies.

Setback or size violations: stop-work, removal, or permit-after-the-fact with fees. Electrical work without permit: immediate correction and fines.

If you are coming from a city with tighter rules, you will find Spokane gives residents more flexibility on shed rules.

ADU Rules

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.

Key details: State Law: HB 1337 + HB 1110. ADUs Per Lot: 2 minimum allowed. Size: Up to 1,000 sq ft. Owner-Occupancy: Cannot be required. Transit Parking: Waived within half-mile.

Unpermitted ADU construction: stop-work order, fines, and mandatory permitting. Non-compliant zoning restrictions by city could trigger state enforcement.

Spokane is more permissive than most cities when it comes to adu rules. That said, there are still limits.

The Bottom Line

Compared to many U.S. cities, Spokane gives residents more room on accessory structures. 5 of the 9 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.

These rules come from Spokane's publicly available municipal code. For complete penalty schedules, exemption details, and answers to common questions, see the individual ordinance pages throughout this guide.