Zoning & Size Limits
| Requirement | Bellevue, WA | Spokane, WA |
|---|
| Allowed Zones | Any lot in a land use district that allows a single-family d | Single-family residential |
| Max Size (Detached) | 1,200 sq ft (Director may approve more for single-floor units in the primary structure or conversions/additions to existing accessory structures) | 1,000 sq ft |
| Max Size (Attached) | 1,200 sq ft, or 40% of the structure, whichever is greater | 800 sq ft |
| Max Height | Detached ADUs: 24 ft to the highest point (28 ft w | 35 feet |
| Parking Required | None under 1,000 sq ft; 1 space for 1,000-2,000 sq ft; none | Studio and 1-bedroom ADUs: none required; larger units subje |
| Owner Occupancy | Not required (removed by Ordinance 6746 in 2023; prohibited | Not required (eliminated by Washington HB 1337), except when |
Setback Requirements
| Setback | Bellevue, WA | Spokane, WA |
|---|
| Rear Setback | Subject to middle-housing dimensional standards (LUC 20.20.538) — Confirm with Bellevue Development Services | Confirm with Spokane Planning (SMC Title 17C) |
| Side Setback | Subject to middle-housing dimensional standards (LUC 20.20.538) — Confirm with Bellevue Development Services | Confirm with Spokane Planning (SMC Title 17C) |
| Front Setback | Per underlying district / middle-housing standards | Confirm with Spokane Planning (SMC Title 17C) |
Permits & Timeline
| Detail | Bellevue, WA | Spokane, WA |
|---|
| Permit Timeline | Several weeks to a few months depending on review queue — Confirm with Bellevue Development Services | 50-75 days |
| Permit Fees | Permit and plan review fees based on project valuation — Confirm with Bellevue Development Services | $2,000-$3,500 |
| Impact Fees | School/transportation impact fees may apply; HB 1337 caps AD | $600-$1,200 |
| Pre-Approved Plans | No city pre-approved plan library — Confirm with B | Limited availability |
Construction Costs
| Cost | Bellevue, WA | Spokane, WA |
|---|
| Avg Build Cost | $180,000-$380,000 | $110,000-$220,000 |
| Cost Per Sq Ft | $200-$350 | $110-$220 |
| Garage Conversion | $90,000-$190,000 | $50,000-$120,000 |
| Prefab ADU | $120,000-$280,000 | $80,000-$180,000 |
Rental Income Potential
| Rental | Bellevue, WA | Spokane, WA |
|---|
| 1BR Avg Rent | $2,500-$2,900/mo | $1,000-$1,450/mo |
| 2BR Avg Rent | $3,100-$3,900/mo | $1,300-$1,900/mo |
| Short-Term Rentals | No citywide STR ban identified — Confirm current short-term | Allowed, but owner-occupancy is required when the lot is use |
| Est. ROI | 6-8% annual return | 8-12% annual return |
Which City Is Better for ADUs?
Bellevue scores 8/10 while Spokane scores 6/10 on our ADU-friendliness index.
Bellevue edges ahead overall. Both cities offer viable ADU development opportunities — the best choice depends on your specific property, budget, and goals.
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