Everything homeowners ask about building an ADU in Spokane — answered with 2026 data.
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.
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.
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 Not allowed. Maximum height is 35 feet. You are allowed up to 1 ADU per lot on a qualifying lot.
Rear setback: 15 feet. Side setback: 5 feet. Front setback: 20 feet. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
1 space per unit. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required (WA state eliminated this requirement). Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Spokane is typically 50-75 days. The plan check process takes approximately 2-3 weeks. Pre-approved plans availability: Limited availability.
Average ADU rental income in Spokane: 1-bedroom units rent for $1,000-$1,450/mo/month, 2-bedroom units for $1,300-$1,900/mo/month. Short-term rentals: Not permitted. Expected ROI: 8-12% annual return.
The minimum lot size for an ADU in Spokane is 5,000 sq ft. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
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.