Spokane allows ADUs in residential zones with reasonable regulations. The city is moderately ADU-friendly, with straightforward permitting and moderate size limits that accommodate most development goals.
Zoning & Size Requirements [1][2]
Yes — Spokane allows ADUs. A detached ADU can typically be up to 1,000 sq ft under current Washington and Spokane zoning rules.
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| Allowed Zones | Single-family residential |
| Max Size (Detached) | 1,000 sq ft |
| Max Size (Attached) | 800 sq ft |
| Max Size (JADU) | N/A (Washington does not use a separate JADU category) |
| Max Height | 35 feet |
| Max Units | Up to 2 ADUs per lot (as of right) |
Setback Requirements [1][2]
Spokane requires a rear setback of about the required distance for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is not required — you can rent it out without living on the property.
| 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) |
| Parking Required | 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 |
| Owner Occupancy | Not required (eliminated by Washington HB 1337), except when the lot is also used as a short-term rental |
| Min Lot Size | None - WA HB 1337 (RCW 36.70A.680) requires cities to allow 2 ADUs on any lot meeting the principal unit's minimum |
Permit Process & Fees
An ADU permit in Spokane typically costs $2,000-$3,500 and takes 50-75 days, through a standard permit review.
| Approval Process | Standard building permit |
| Review Timeline | 50-75 days |
| Permit Fees | $2,000-$3,500 |
| Impact Fees | $600-$1,200 |
| Plan Check | 2-3 weeks |
| Pre-Approved Plans | Limited availability |
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Construction Costs [3][4]
Building an ADU in Spokane typically costs $110,000-$220,000 ($110-$220 per sq ft); a garage conversion runs $50,000-$120,000.
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| Average Build Cost | $110,000-$220,000 |
| Cost per Sq Ft | $110-$220 |
| Garage Conversion | $50,000-$120,000 |
| Prefab ADU (Installed) | $80,000-$180,000 |
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders.
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Rental Income Potential [5][6]
A 2-bedroom ADU in Spokane rents for around $1,300-$1,900/mo, an estimated 8-12% annual return.
| Avg Rent (1 Bedroom) | $1,000-$1,450/mo |
| Avg Rent (2 Bedroom) | $1,300-$1,900/mo |
| Short-Term Rental | Allowed, but owner-occupancy is required when the lot is used as a short-term rental |
| Est. Annual ROI | 8-12% annual return |
Explore Prefab ADU Options
Prefab ADUs can save 20-40% vs. traditional construction and cut build time in half.
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Recent Law Changes
What's Changed Recently
- Washington HB 1337 (effective July 2023): requires up to 2 ADUs per lot, at least 1,000 sq ft each, no owner-occupancy except for short-term rentals, and parking limits near major transit. Spokane's compliance deadline was June 30, 2025
- Washington HB 1345 (signed March 2026, effective June 11, 2026): a county-option law for detached ADUs on rural parcels outside urban growth areas — does not change Spokane's in-city rules
- Spokane now allows two ADUs per lot as a matter of right under HB 1337
- Owner-occupancy is required only when the lot with an ADU is also used as a short-term rental
Tips for Building an ADU in Spokane
- Spokane's lower property costs mean excellent cash flow on ADU rentals
- Long-term rental market is stable and strong
- More conservative approach than western Washington cities; straightforward rules
- Highest ROI of Washington cities due to lower construction and land costs
ADU Builders in Spokane
Looking for an ADU builder in Spokane? ADU projects need a contractor experienced with local zoning, the permit process, and utility connections — not every general contractor has built one. We match Spokane homeowners with experienced local ADU contractors who provide free, no-obligation quotes. Getting at least three bids typically saves 20-40% on the same scope.
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Ordinance amending Title 17 of the Spokane Municipal Code (ADUs / HB 1337) — City of Spokane Municipal Code — Accessed 2026-06-28
- Washington HB 1337 (2023) — Washington State Legislature Government Data — Accessed 2026-06-28
- Angi — ADU Construction Cost Data Market Data — Accessed 2026-02-24
- Angi — Local ADU Contractor Costs Market Data — Accessed 2026-02-24
- Zillow Rental Manager — Market Rent Data Market Data — Accessed 2026-02-24
- HUD Fair Market Rents Government Data — Accessed 2026-02-24
- ADU Overview — City of Spokane Infill Housing Planning Department — Accessed 2026-02-24
- Washington ADU Legislation (HB 1337) Government Data — Accessed 2026-02-24
Frequently Asked Questions
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