An ADU builder in Spokane is a licensed contractor who designs and constructs accessory dwelling units — detached backyard units, garage conversions, attached additions, and junior ADUs (JADUs). Because an ADU is a complete second dwelling, the builder coordinates foundation, framing, plumbing, electrical, and HVAC work and pulls it through Spokane's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in Washington.
What ADU Builders Cost in Spokane [16][17]
Based on our Spokane cost data, expect the following ranges from local ADU builders. Quotes for the same scope typically vary 20-40% between contractors, so getting at least three bids is the single best way to control cost.
| New Detached ADU (all-in) | $130,000-$260,000 |
| Cost per Sq Ft | $200-$400 |
| Garage Conversion | $50,000-$120,000 |
| Prefab / Modular ADU (installed) | $135,000-$280,000 |
| City Permit & Plan Review | About $2,000-$3,200 in city fees for a $150,000-$300,000 ADU (2025 New SFR/ADU fee table: $65 processing, plan review at 50% of the permit fee, $100 stormwater review, 2.5% technology fee, $6.50 state fee). A CPI-adjusted 2026 schedule now applies; confirm with the DSC. |
| Impact Fees | Transportation impact fees apply to new dwelling units by service area (SMC 17D.075; schedule in 17D.075.180, Ordinance C36514, indexed up to 5% a year). State law caps an ADU's fee at 50% of the single-family fee (RCW 36.70A.681(1)(a)). The current dollar figure was not readable; ask the DSC for your service area's rate. |
For a full line-item breakdown, see our Spokane ADU cost guide. To confirm what you're allowed to build before you hire, review the Spokane ADU rules (max detached size: 1,000 sq ft of floor area (SMC 17C.300.110(A)(2)). Building footprint up to 1,200 sq ft in every residential zone (Table 17C.111.205-2), counted within the lot's total building coverage cap of 50% in RA, 65% in R1, 80% in R2 and 100% in RMF/RHD (Table 17C.111.205-1, note 5).; owner-occupancy: Not required. The only exception: if the lot also has a short-term rental under Chapter 17C.316 SMC, one unit must be the owner's principal residence for more than six months a year and cannot be rented (SMC 17C.300.110(B)); the ADU approval is then transferable only to a buyer who will owner-occupy (SMC 17C.300.140).).
Get Free ADU Quotes in Spokane
Tell us about your project and we'll pass it to ADU builders serving Spokane. Free, no obligation — you choose who to work with. We don't have builders in every area yet; if nobody covers yours, we'll email you to say so.
Takes about a minute.
Up to 5 independent local ADU builders — never more, and we tell them nothing you don't submit here.
Compare quotes, verify license & insurance, hire (or don't). No spam either way.
🔒 Your info is secure. We share it only with contractors quoting your project. No spam, no obligation.
Just browsing? Search ADU builders near you by ZIP code.
How to Vet an ADU Builder in Spokane
- License: Confirm a current contractor's license in Washington and that it's in good standing. Ask for the license number and verify it with the state board.
- ADU-specific experience: Ask how many ADUs they've completed in or near Spokane and request addresses or photos. ADU permitting and setbacks differ from a kitchen remodel.
- Portfolio & references: Get references from recent ADU clients and, if possible, visit a finished unit.
- Insurance: Verify general liability and workers' compensation coverage. Ask for a certificate of insurance.
- Written, detailed bid: Insist on an itemized, fixed-price or clearly-scoped bid — not a verbal estimate. It should state whether permits (About $2,000-$3,200 in city fees for a $150,000-$300,000 ADU (2025 New SFR/ADU fee table: $65 processing, plan review at 50% of the permit fee, $100 stormwater review, 2.5% technology fee, $6.50 state fee). A CPI-adjusted 2026 schedule now applies; confirm with the DSC.), plan check (Plan review is 50% of the building permit fee for new single-family, ADU and duplex permits and is paid at submittal before the plans are routed (2025 Development Services Fee Schedule); for a $200,000 ADU that is $736 of a $2,416 total.), and impact fees (Transportation impact fees apply to new dwelling units by service area (SMC 17D.075; schedule in 17D.075.180, Ordinance C36514, indexed up to 5% a year). State law caps an ADU's fee at 50% of the single-family fee (RCW 36.70A.681(1)(a)). The current dollar figure was not readable; ask the DSC for your service area's rate.) are included.
- Permit handling: Confirm they manage Spokane's permit process ("Building permit plus a certificate of occupancy from the Development Services Center, 3rd floor City Hall (SMC 17C.300.120); no land-use hearing or design review. Mechanical, electrical and plumbing permits are separate. The ADU uses the principal dwelling's utilities and street address (SMC 17C.300.130(C)).", typically The city publishes no ADU-specific review time. State law (RCW 36.70B.080(1)(d)) makes 65 days from a complete application the default for permits that need no public notice, unless Spokane has adopted its own periods; ask the Development Services Center (509-625-6300).) and who is responsible if revisions are required.
- Payment schedule: Avoid large upfront payments. A reasonable schedule ties payments to completed milestones.
Questions to Ask Before You Hire
- How many ADUs have you built in Spokane in the last two years?
- Is your bid fixed-price, and what would trigger a change order?
- Are permits, plan check, and utility connection fees included?
- What's a realistic timeline, including permit review (The city publishes no ADU-specific review time. State law (RCW 36.70B.080(1)(d)) makes 65 days from a complete application the default for permits that need no public notice, unless Spokane has adopted its own periods; ask the Development Services Center (509-625-6300).) and construction?
- Who is my point of contact and how are delays communicated?
- What warranty do you provide on workmanship?
- Can you share three recent Washington ADU client references?
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders.
Some links on this page are affiliate links. We may earn a commission at no extra cost to you. Learn more
Are you an ADU builder? Get Spokane leads
Homeowners on this page submit real ADU project requests in Spokane. Each one goes to up to five local builders — that is what the homeowner agrees to — so claiming never takes it from anyone and there is no bidding. In practice far fewer ever make contact, which is why the number is five rather than three. A flat $50 only on the leads you accept: no subscription, no contract, and you deal with the homeowner directly.
Get Spokane ADU Leads →Frequently Asked Questions
How much do ADU builders charge in Spokane?
How do I find a good ADU builder in Spokane?
Do ADU builders in Spokane handle permits?
How long does it take to build an ADU in Spokane?
Get Free ADU Builder Quotes in Spokane
Compare bids from experienced local Spokane ADU builders. Free, no obligation.
Get Free Quotes →