Jurisdiction
ADUs in Unincorporated Spokane County
These rules apply to parcels in unincorporated Spokane County, meaning lots that are not inside any city. The county's primary ADU documents are the Building and Planning sheets BP-75 (detached) and BP-76 (attached).
Identify your jurisdiction first
Spokane County contains several incorporated cities, including Spokane, Spokane Valley, Cheney, Liberty Lake, and Airway Heights. Each city writes its own ADU rules. The standards on this page apply only to unincorporated county land. If your parcel is inside a city, use that city's page instead. Getting this step right matters, because the allowed size, parking, and process can differ between the county and a city.
Unincorporated Spokane County ADU rules at a glance
Each value is a verification placeholder until confirmed against the county Building and Planning sheets and zoning code. Do not rely on a figure here until the operator replaces its placeholder with a cited value.
| Rule | Current unincorporated county standard |
|---|---|
| Allowed ADU types | [VERIFY: operator to confirm which ADU types are permitted on unincorporated county parcels (detached per BP-75, attached per BP-76) from https://www.spokanecounty.gov (Building and Planning, BP-75 and BP-76, county zoning code)] |
| Maximum ADUs per lot | [VERIFY: operator to confirm the maximum number of ADUs per lot in unincorporated county after HB 1337 from https://www.spokanecounty.gov (Building and Planning, BP-75 and BP-76, county zoning code)] |
| Maximum ADU size | [VERIFY: operator to confirm the maximum ADU size and any percent-of-primary cap in the county code from https://www.spokanecounty.gov (Building and Planning, BP-75 and BP-76, county zoning code)] |
| Maximum height | [VERIFY: operator to confirm the maximum ADU height in the county code from https://www.spokanecounty.gov (Building and Planning, BP-75 and BP-76, county zoning code)] |
| Setbacks | [VERIFY: operator to confirm ADU setbacks under the county zoning code from https://www.spokanecounty.gov (Building and Planning, BP-75 and BP-76, county zoning code)] |
| Off-street parking | [VERIFY: operator to confirm the off-street parking requirement for a county ADU, accounting for HB 1337 limits from https://www.spokanecounty.gov (Building and Planning, BP-75 and BP-76, county zoning code)] |
| Owner-occupancy | [VERIFY: operator to confirm whether owner-occupancy is required in the county, given HB 1337 from https://www.spokanecounty.gov (Building and Planning, BP-75 and BP-76, county zoning code)] |
| Septic and water | [VERIFY: operator to confirm any septic capacity or water connection requirements that apply to a county ADU from https://www.spokanecounty.gov (Building and Planning, BP-75 and BP-76, county zoning code)] |
| Permit fees and charges | [VERIFY: operator to confirm current county ADU permit fees and any applicable charges from https://www.spokanecounty.gov (Building and Planning, BP-75 and BP-76, county zoning code)] |
A note on septic and wells
Unlike most city lots, many unincorporated parcels rely on a septic system and sometimes a private well rather than municipal sewer and water. Septic capacity can be a deciding feasibility factor for a county ADU, so it is worth confirming early. The builder you are matched with and the county health and building offices assess this.
The permit process in the county
ADU permits for unincorporated parcels run through Spokane County Building and Planning. The BP-75 and BP-76 sheets outline the county's ADU requirements. Confirm the current submittal checklist, review steps, and fees with the county. Our homeowner permit guide explains what to expect.
Unincorporated Spokane County ADU questions
- How do I know if my lot is in unincorporated Spokane County?
- If your parcel is not inside any city, the unincorporated Spokane County rules apply. Cities within the county, including Spokane, Spokane Valley, Cheney, Liberty Lake, and Airway Heights, have their own codes. Identifying your jurisdiction first is essential because the rules differ.
- What are the Spokane County BP-75 and BP-76 sheets?
- BP-75 and BP-76 are Spokane County Building and Planning information sheets for ADUs, BP-75 for detached units and BP-76 for attached units. They are the primary county documents to confirm current requirements.
- Do I need extra parking for an ADU in unincorporated Spokane County?
- County zoning has historically expected off-street parking for an ADU in addition to the main residence, but Washington HB 1337 limits some parking requirements. Confirm the current county parking standard before you plan around it.
References and primary sources
Regulatory and fee specifics on this page should be confirmed against the current primary sources below. Items marked VERIFY are pending operator confirmation before promotion.
- Spokane County Building and Planning (spokanecounty.gov) BP-75 (detached ADU), BP-76 (attached ADU), and the county zoning code.
- Washington HB 1337 and RCW 36.70A State ADU law and the Growth Management Act.
Related
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