ADU Questions & Answers: Spokane, WA

Can I build an ADU in Spokane?

Yes, ADUs are allowed in Single-family residential in Spokane, WA. The maximum size for a detached ADU is 1,000 sq ft. Attached ADUs can be up to 800 sq ft. Spokane has an ADU-friendliness score of 6/10. Check our full Spokane ADU rules page for complete zoning details.

How much does it cost to build an ADU in Spokane?

ADU construction in Spokane typically costs $110,000-$220,000. The cost per square foot averages $110-$220. Garage conversions are more affordable at $50,000-$120,000, while prefab ADUs cost $80,000-$180,000. Permit fees add $2,000-$3,500 to your budget. See our detailed Spokane ADU cost guide.

What are the ADU size limits in Spokane?

Detached ADUs in Spokane can be up to 1,000 sq ft. Attached ADUs are limited to 800 sq ft. Junior ADUs (JADUs) have a cap of N/A (Washington does not use a separate JADU category). Maximum height is 35 feet. You are allowed up to Up to 2 ADUs per lot (as of right) on a qualifying lot.

What are the setback requirements for ADUs in Spokane?

Rear setback: Confirm with Spokane Planning (SMC Title 17C). Side setback: Confirm with Spokane Planning (SMC Title 17C). Front setback: Confirm with Spokane Planning (SMC Title 17C). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.

Do I need parking for an ADU in Spokane?

Studio and 1-bedroom ADUs: none required; larger units subject to HB 1337 limits (none within 1/2 mile of major transit). Confirm with Spokane Planning. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.

Is owner-occupancy required for ADUs in Spokane?

Not required (eliminated by Washington HB 1337), except when the lot is also used as a short-term rental. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.

How long does it take to get an ADU permit in Spokane?

The ADU permit review timeline in Spokane is typically 50-75 days. Plan check: 2-3 weeks. Pre-approved plans availability: Limited availability.

How much can I rent my ADU for in Spokane?

Average ADU rental income in Spokane: 1-bedroom units rent for $1,000-$1,450/month, 2-bedroom units for $1,300-$1,900/month. Short-term rentals: Allowed, but owner-occupancy is required when the lot is used as a short-term rental. Expected ROI: 8-12% annual return.

What is the minimum lot size for an ADU in Spokane?

The minimum lot size for an ADU in Spokane is None - WA HB 1337 (RCW 36.70A.680) requires cities to allow 2 ADUs on any lot meeting the principal unit's minimum. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.

Can I convert my garage into an ADU in Spokane?

Garage conversions are one of the most popular and affordable ADU options. In Spokane, a garage conversion typically costs $50,000-$120,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.

About this information: This page is an informational summary of publicly available regulations - it is not legal, financial, or professional advice, and it is not a substitute for confirming requirements with your local planning department. Rules change frequently; always verify current requirements before designing, budgeting, or building. Last verified: 2026-07-07. Contractors we introduce are independent businesses - verify license and insurance directly before hiring. Spotted an error? Tell us - we verify against primary sources and correct quickly.