Planning-level pricing guide by ADUWizard.com
Updated for 2026 budgeting
Spokane is the number I point people to when they assume every Washington ADU costs Seattle money. It does not. Eastern Washington labor is cheaper, the sites are generally flatter and easier, and the permit path is fast and inexpensive. Spokane is where a small detached ADU can actually pencil out for a normal homeowner.
This is the Spokane version of the real budgeting guide, written for a garage conversion, basement unit, or detached ADU in 2026.
Quick disclaimer: A budgeting guide, not a quote or legal advice. Even in Spokane, utility runs and older-home surprises move budgets, and Washington sales tax (around 9% here) still applies. Use these ranges to compare bids.
Spokane ADU Cost in 2026 (Quick Answer)
| Project scenario | Typical size | Spokane all-in cost |
|---|---|---|
| Garage conversion | 400–650 sf | $50k–$120k |
| Basement / interior ADU | 450–800 sf | $95k–$210k |
| Attached ADU / addition | 500–900 sf | $130k–$260k |
| Detached new-build | 500–1,000 sf | $110k–$260k |
| Prefab / modular installed | 500–900 sf | $135k–$280k |
Overall, Spokane ADU construction typically runs $110k–$220k, with garage conversions the cheapest path at roughly $50k–$120k.
Spokane ADU Rules That Affect Cost (2026)
Spokane follows Washington’s statewide HB 1337 framework, and its local process is refreshingly light and cheap.
| Rule | Spokane standard (2026) | Why it matters for cost |
|---|---|---|
| ADUs per lot | Up to two in residential zones | Room to add over time |
| Max detached size | Up to about 1,000 sf | A real 1–2 bedroom unit is by-right |
| Max height | Generally about 20 ft | Keeps most units single-story |
| Setbacks | Roughly 15 ft rear as a common reference, varies by zone | Confirm your zone before you design |
| Parking | None for studios and 1-beds; a 2-bed may need one space | Saves paving on smaller units |
| Owner-occupancy | Not required | Removes a financing and resale drag |
| Permit fees / review | Commonly $2,000–$3,500, review around 50–75 days | Among the cheapest, fastest in the state |
What drives cost in Spokane: mostly utilities and older-home conversion surprises. Slope and soils matter less here than around Puget Sound, which keeps sitework budgets down.
Spokane ADU Cost by Type and Size (2026)
| Type | Typical size | All-in range |
|---|---|---|
| Garage conversion | 400–650 sf | $50k–$120k |
| Basement / interior | 450–800 sf | $95k–$210k |
| Attached addition | 500–900 sf | $130k–$260k |
| Detached new-build | 500–1,000 sf | $110k–$260k |
| Size | Conversion | Detached |
|---|---|---|
| 500 sf | $50k–$120k | $110k–$200k |
| 700 sf | $85k–$180k | $135k–$235k |
| 1,000 sf | $120k–$210k | $170k–$260k |
All-in cost per square foot in Spokane and Eastern Washington runs roughly $190–$340 for conversions and $260–$450 for detached units.
Example Spokane Budget: 600 sf Detached ADU (1-Bed)
| Category | Budget |
|---|---|
| Design + engineering | $10,000–$20,000 |
| Permits + fees | $2,000–$3,500 |
| Sitework + utilities | $12,000–$35,000 |
| Foundation + framing + envelope | $55,000–$100,000 |
| MEP | $28,000–$50,000 |
| Interior finishes | $22,000–$45,000 |
| Sales tax + contingency | $16,000–$32,000 |
| Total all-in | $130,000–$240,000 |
Spokane ADU Permit Timeline
Spokane’s permit review commonly runs 50–75 days, one of the faster and cheaper processes in the state, with fees often in the $2,000–$3,500 range. Add design time before and construction after, and a straightforward project can finish in well under a year.
FAQs (Spokane)
How much does an ADU cost in Spokane in 2026?
Budget roughly $50k–$120k for a garage conversion and $110k–$260k for a detached ADU. Spokane is the most affordable major ADU market in Washington by a wide margin.
Why is Spokane so much cheaper than Seattle?
Lower labor costs, easier and flatter sites, a lighter and cheaper permit process, and a lower sales-tax rate (around 9% versus 10.25% in Seattle). The gap on a detached unit can be well over $200k.
How big can a Spokane ADU be?
Detached ADUs are generally allowed up to about 1,000 sf, with a height limit near 20 feet. Confirm your zone’s specific setback and size details before you design.
Do I need parking for a Spokane ADU?
Studios and one-bedroom ADUs generally require no additional parking; a two-bedroom unit may need one space. This keeps sitework low on smaller units.
How fast and cheap is the Spokane permit process?
Review commonly runs 50–75 days, with fees often in the $2,000–$3,500 range, among the quickest and cheapest in Washington.
For the statewide view, see our Washington ADU cost guide, compare pricier Seattle ADU costs, and check the Data Hub. City permitting details are at the City of Spokane.