Spokane metro ADU quotes
ADU construction in Spokane, Spokane Valley, and Spokane County
The work covers detached backyard units, attached additions, garage conversions, and basement junior ADUs. A licensed local builder who serves your jurisdiction prices the project, free. We are paid by the builder, not by you.
What is an ADU?
An accessory dwelling unit (ADU) is a smaller, self-contained second home on the same lot as a primary house. It can be a detached backyard unit, an attached addition, a garage conversion, a basement unit, or a junior ADU. Spokane-area homeowners build them for rental income, multigenerational living, guest or office space, and added property value.
Rules, cost, and a free quote
This site publishes current, sourced guides on Spokane ADU rules, permits, and cost, so you can plan before you spend anything. When you are ready to price a build, one form gets you a free quote, and the design, permitting, and construction are handled by the builder.
How it works
- 1
Tell us about your project
Share your jurisdiction, the ADU type you are considering, and a few notes about your lot and timeline. It takes a couple of minutes.
- 2
A free quote from a local builder
A builder who serves your jurisdiction in the Spokane area looks at the lot and puts the scope and the price in writing. It costs you nothing.
- 3
The work gets scheduled
Design, permitting, and construction are handled by the builder you contract with directly. There is no obligation at any point.
The three jurisdictions, and every ADU type
ADU rules differ by jurisdiction, so the first step is identifying which one your lot falls under: the City of Spokane, unincorporated Spokane County, or Spokane Valley. Every ADU type is covered, including new detached units, attached ADUs and additions, garage conversions, basement units, and junior ADUs. Use the menu above to open the rules for your jurisdiction or any ADU type.
Start with these guides
Guide
Can I Build an ADU on My Lot in Spokane?
A feasibility checklist: zoning, lot, utilities, and your jurisdiction.
Read more →Guide
ADU Cost in Spokane
A sourced, Spokane-specific breakdown of what an ADU costs in 2026.
Read more →Guide
How to Choose an ADU Builder in Spokane
What to look for, what to ask, and how a referral helps.
Read more →What it costs, and what happens after you send it
- What does an ADU cost in the Spokane area?
- detached new-build $110,000 to $260,000, garage conversion $50,000 to $120,000, prefab or modular installed $80,000 to $180,000. Add roughly $3,000 to $5,000 in permit, plan review and impact fees, which is an estimate from one source rather than a published fee schedule, so confirm it with your permitting jurisdiction.
- How solid are those numbers?
- Treat them as planning ranges, not prices. They come from two third-party estimator sites, ADU Zoning and ADU Wizard, both read in full on 2026-08-17, neither of them a government publication. The two land in nearly the same place on total project cost, which is why totals are shown here. They differ by roughly a factor of two on cost per square foot, so a per-square-foot rate is not a reliable way to budget an ADU here and none is quoted.
- How fast will someone get back to me?
- Your request goes to an independent local ADU builder, usually within about an hour during the day. The builder then contacts you to look at the property and price the project on their own schedule.
- What types are covered?
- Detached ADUs, attached ADUs, garage conversions and basement junior ADUs. See every type.
Only a builder standing on your lot can price your actual project.
Get a free quote from a Spokane ADU builder
Tell us about your lot and project. A builder who serves your jurisdiction prices it, free and with no obligation.
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