ADU Rules in Spokane, WA (2026)
ADU rules, permit requirements, size limits, and fees for Spokane, WA. Source-cited from official municipal code.
Yes, ADUs are allowed in Spokane, WA.
Spokane, WA permits accessory dwelling units (ADUs) on residential properties. ADUs — also called granny flats, in-law units, backyard cottages, or secondary suites — are secondary housing units on a single-family or multifamily lot. State and local law actively preempts local restrictions, making ADU approval a streamlined ministerial process. In Spokane, the City of Spokane Building Services handles ADU permit applications. Below you will find the current size limits, setbacks, fees, and timeline for building an ADU in Spokane.
ADU Size Limits
ADU Size Limits in Spokane: Detached ADU: up to 1000 sq ft (max height: 24 feet). Attached ADU: 1000 sq ft. Washington does not use the California JADU concept. Spokane allows detached and attached ADUs per SMC Chapter 17C and Washington HB 1337 requirements. Up to 2 ADUs permitted per lot under state law. ADU maximum size is 1,000 sqft or the size of the primary dwelling, whichever is smaller, in standard residential zones.
| Type | Max Size | Max Height |
|---|---|---|
| Detached ADU | 1000 sq ft | 24 feet |
| Attached ADU | 1000 sq ft | Same as primary dwelling height limit per zone |
Permit Fees
ADU Permit Fees in Spokane: Plan check fee: $200–$900. Building permit fee: Based on construction value — typically $500–$2,500. Impact fees: Varies — Spokane charges utility connection fees. School fees: None or N/A. Total estimated permit cost: $1,000–$5,000 total fees. Spokane's ADU fees are significantly lower than Seattle's. Contact Spokane Planning for current fee schedule. Avista Utilities (electric and gas) connection fees for new ADU services.
| Fee Type | Amount |
|---|---|
| Plan Check | $200–$900 |
| Building Permit | Based on construction value — typically $500–$2,500 |
| Impact Fees | Varies — Spokane charges utility connection fees |
| School Fees | None |
| Total Estimate | $1,000–$5,000 total fees |
Permit Timeline
Spokane ADU Permit Timeline: Spokane Planning Department: plan review typically 3-6 weeks. Spokane has implemented expedited ADU review to comply with HB 1337. Construction 4-10 months. Apply through the City of Spokane Building Services online permit portal. Phone: (509) 625-6300.
Setback Requirements
ADU Setback Requirements in Spokane: Front setback: Same as zone standard. Side setback: 5 feet. Rear setback: 5 feet. Detached ADU setbacks: minimum 5 ft from side and rear property lines per SMC Chapter 17C and HB 1337 requirements. Front setback follows zone standard. Spokane's residential lots tend to be larger than Seattle's — setback compliance is generally less challenging. Alley-accessed properties may have ADUs near the alley.
Parking Requirements
Parking Requirements: No additional parking required for ADUs within 0.25 miles of a major transit stop per Washington HB 1337. Spokane Transit Authority (STA) operates bus routes throughout Spokane — verify transit proximity. Otherwise, 1 space per ADU. Spokane is more car-dependent than Seattle but has a functional transit system.
Restrictions & Requirements
- ADU must be on same lot as primary residence
- Up to 2 ADUs allowed per lot per Washington HB 1337
- ADU cannot be sold separately from the primary lot
- Must comply with SMC Chapter 17C setback and coverage standards
How Many ADUs Are Allowed?
Number of ADUs Allowed in Spokane: Single-family lots: 2 ADUs per single-family lot per Washington HB 1337. Multifamily properties: Subject to zone density provisions. Washington HB 1337 requires Spokane to allow at least 2 ADUs per single-family lot. Unlike Seattle, where this was already the law since 2019, Spokane updated its code in compliance with the 2023 state mandate.
Single-Family Lots
2 ADUs per single-family lot per Washington HB 1337
Multifamily Properties
Subject to zone density provisions
State Law & Preemption
State Preemption: Washington House Bill 1337 (2023) requires all Washington cities and counties to allow at least 2 ADUs per single-family residential lot by-right. Removes owner-occupancy requirements statewide. Limits off-street parking requirements for ADUs within 0.25 miles of a major transit stop. Effective July 23, 2023. Spokane has updated its Municipal Code to comply with HB 1337. Spokane's housing affordability makes it one of the more accessible ADU markets in Washington. Washington does not use the California JADU concept.
Historic District Considerations
Historic District Requirements: Spokane has 4 historic districts where additional design review may be required for ADU construction. Design review approval is required before obtaining a building permit for properties in historic overlay zones. Spokane has several significant historic districts including Browne's Addition (one of the oldest residential neighborhoods in the Pacific Northwest), the Downtown Spokane Historic District, Rockwood Boulevard, and other designated areas. Spokane's 1974 World's Fair (Expo '74) is historically significant — the Riverfront Park site reflects this heritage. Certificate of Appropriateness required for exterior changes in designated historic overlay zones. Look up historic district boundaries at: https://my.spokanecity.org/planning/historic-preservation/
Frequently Asked Questions
Can I build an ADU in Spokane?
Yes. Spokane, WA allows accessory dwelling units. On a single-family lot you can build 2 ADUs per single-family lot per Washington HB 1337.
How big can an ADU be in Spokane?
The maximum size for a detached ADU in Spokane is 1,000 square feet.
How long does it take to get an ADU permit in Spokane?
The typical ADU permit timeline in Spokane is Spokane Planning Department: plan review typically 3-6 weeks. Spokane has implemented expedited ADU review to comply with HB 1337. Construction 4-10 months.. Total estimated permit fees are $1,000–$5,000 total fees.
Do I need extra parking for an ADU in Spokane?
No, Spokane does not require additional parking for ADUs.
Do I have to live on-site to have an ADU in Spokane?
No, owner-occupancy is not required for ADUs in Spokane.
Source: Spokane Municipal Code Chapter 17C — Zoning; Washington HB 1337 (2023). Last verified April 6, 2026. View source