Jurisdiction
ADUs in the City of Spokane
These rules apply to lots inside Spokane city limits and are drawn from the current Spokane Municipal Code, Chapter 17C.300. The City of Spokane updated its ADU code to comply with Washington HB 1337, so several older figures are superseded.
Currency of these rules
The ADU chapter (SMC 17C.300) is current as of Ordinance C36696, effective July 11, 2025, and the dimensional standards table (Table 17C.111.205-2) is current as of Ordinance C36810, effective January 18, 2026. The older 2016 figures (a 60 foot front setback, one ADU per lot, and owner-occupancy) are fully superseded and are not published here.
City of Spokane ADU rules at a glance
Before you design, confirm whether your lot can support an ADU under these standards.
| Rule | Current City of Spokane standard |
|---|---|
| Allowed ADU types | Detached and attached ADUs (SMC Chapter 17C.300). A basement conversion is handled under the same chapter. |
| Maximum ADUs per lot | Two per lot in the RA, R1, R2, RMF, and RHD residential zones (SMC 17C.300.100). |
| Maximum ADU size | Up to 1,000 sq ft of floor area, detached or attached (the garage is excluded, and the principal structure must be at least 1,000 sq ft). A basement or attic conversion may exceed the cap. Maximum building footprint is 1,200 sq ft (SMC 17C.300.110(1) and Table 17C.111.205-2). |
| Maximum height | 25 ft, all zones (Table 17C.111.205-2). |
| Setbacks (detached ADU) | Side setback matches the primary structure: 3 ft if the lot is 40 ft wide or less, otherwise 5 ft. Rear setback is 0 ft with an alley, 5 ft without one. A side or rear setback can reduce to 0 ft with a signed neighbor waiver (Table 17C.111.205-2, note 5). |
| Off-street parking | Per SMC Chapter 17C.230. Studio and one-bedroom ADUs require no additional parking, and none is required within one-half mile of a major transit stop (SMC 17C.300.130, HB 1337). |
| Owner-occupancy | Not required, except where the lot also operates a short-term rental under SMC Chapter 17C.316, in which case one unit on the lot must be owner-occupied (SMC 17C.300.110(2)). |
| Permit | A building permit plus a certificate of occupancy from City of Spokane Building Services. |
Fees: permit, water and sewer charges, and impact fees
In Washington, the charge people often call a system development charge is the general facilities charge (GFC) for water and sewer, plus the transportation impact fee. For the City of Spokane:
- Water general facilities charge (2026): 3,366 dollars for a 5/8 inch meter (typical for an ADU), 8,415 dollars for a 1 inch meter, and 26,930 dollars for a 2 inch meter.
- Wastewater (sewer) general facilities charge (2026): 4,887 dollars for a 5/8 inch meter (SMC 13.03.0734). Combined with the water GFC, a typical ADU connection is about 8,253 dollars in 2026 general facilities charges. The city does not waive these connection charges.
- Transportation impact fee for an ADU: as low as about 106 dollars in the high-density transit core, up to roughly 1,000 dollars farther from the core (SMC 17D.075). HB 1337 caps ADU impact fees at 50 percent of the principal unit's.
- Building permit fee: valuation-based, so there is no single flat figure. Use the city's official residential fee estimator.
The permit process in the City of Spokane
ADU permitting runs through the City of Spokane Development Services Center, which reviews zoning and building requirements and issues the permits. Our homeowner permit guide walks through what to expect without copying the application form.
City of Spokane permit counter: 3rd Floor, City Hall, 808 West Spokane Falls Boulevard, Spokane, WA 99201. Phone 509.625.6300. Email [email protected].
City of Spokane ADU questions
- Do I need a permit to build an ADU in the City of Spokane?
- Yes. An ADU requires a building permit and a certificate of occupancy from City of Spokane Building Services, reviewed under Spokane Municipal Code Chapter 17C.300. The builder you are matched with manages the permit process. See our Spokane ADU permits guide.
- How many ADUs can I have on one lot in the City of Spokane?
- Up to two ADUs per lot in the RA, R1, R2, RMF, and RHD residential zones (SMC 17C.300.100), consistent with Washington HB 1337. The older 2016 one-ADU-per-lot rule is superseded.
- How big can an ADU be in the City of Spokane?
- An ADU may be up to 1,000 square feet of floor area, with a maximum building footprint of 1,200 square feet and a maximum height of 25 feet (SMC 17C.300.110 and Table 17C.111.205-2). A basement or attic conversion may exceed the 1,000 square foot cap.
- Is owner occupancy required for a Spokane ADU?
- No, not as a general rule. Owner-occupancy applies only where the lot also operates a short-term rental under SMC Chapter 17C.316, in which case one unit on the lot must be owner-occupied (SMC 17C.300.110(2)).
References and primary sources
Regulatory and fee specifics on this page are cited to the current primary sources below. Confirm any figure against its source for your specific parcel before you rely on it.
- Spokane Municipal Code Chapter 17C.300, Accessory Dwelling Units (my.spokanecity.org) Types, count, size, parking, owner-occupancy (ORD C36696).
- Spokane Municipal Code Table 17C.111.205-2 (my.spokanecity.org) Height, footprint, and setbacks (ORD C36810).
- City of Spokane residential fee estimator (my.spokanecity.org) Valuation-based building permit fee.
- City of Spokane general facilities charges (my.spokanecity.org) Water and sewer GFC schedule and zone map.
- RCW 36.70A.681 (app.leg.wa.gov) HB 1337 ADU requirements.
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