Zoning & Size Limits
| Requirement | Tacoma, WA | Spokane, WA |
|---|
| Allowed Zones | Residential zones (most) | Single-family residential |
| Max Size (Detached) | 1,000 sq ft living area | 1,000 sq ft |
| Max Size (Attached) | 1,000 sq ft living area | 800 sq ft |
| Max Height | 35 feet | 35 feet |
| Parking Required | Not required (per Washington HB 1337) | Studio and 1-bedroom ADUs: none required; larger units subje |
| Owner Occupancy | Not required | Not required (eliminated by Washington HB 1337), except when |
Setback Requirements
| Setback | Tacoma, WA | Spokane, WA |
|---|
| Rear Setback | 15 feet (no setback required from an alley) | Confirm with Spokane Planning (SMC Title 17C) |
| Side Setback | 5 feet (8 feet if the main entrance faces the side property line) | Confirm with Spokane Planning (SMC Title 17C) |
| Front Setback | Per underlying zone; Confirm with Tacoma Permits | Confirm with Spokane Planning (SMC Title 17C) |
Permits & Timeline
| Detail | Tacoma, WA | Spokane, WA |
|---|
| Permit Timeline | 40-60 days | 50-75 days |
| Permit Fees | $1,800-$2,800 | $2,000-$3,500 |
| Impact Fees | $500-$900 | $600-$1,200 |
| Pre-Approved Plans | Available for common types | Limited availability |
Construction Costs
| Cost | Tacoma, WA | Spokane, WA |
|---|
| Avg Build Cost | $135,000-$270,000 | $110,000-$220,000 |
| Cost Per Sq Ft | $125-$245 | $110-$220 |
| Garage Conversion | $65,000-$155,000 | $50,000-$120,000 |
| Prefab ADU | $100,000-$230,000 | $80,000-$180,000 |
Rental Income Potential
| Rental | Tacoma, WA | Spokane, WA |
|---|
| 1BR Avg Rent | $1,300-$1,750/mo | $1,000-$1,450/mo |
| 2BR Avg Rent | $1,650-$2,300/mo | $1,300-$1,900/mo |
| Short-Term Rentals | Restricted to primary residence owners | Allowed, but owner-occupancy is required when the lot is use |
| Est. ROI | 7-9% annual return | 8-12% annual return |
Which City Is Better for ADUs?
Tacoma scores 8/10 while Spokane scores 6/10 on our ADU-friendliness index.
Tacoma 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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