We don't quote per-square-foot averages and revise mid-project. You get a fixed-price contract before we break ground — and these tiers are how we get there.
Code-compliant turn-key DADU with smart, durable finishes. Built for rental income or guest space.
Our most popular tier. Architect-led design, custom millwork, and full Pacific Northwest material palette.
Custom architecture, premium materials, structural glass, and integrated landscape design. Our flagship work.
Estimates use 2025 Puget Sound averages from our last 24 months of completed builds. Final fixed-price proposal requires a feasibility study of your lot.
All-in median in 2026 for a code-built turn-key DADU: $330–$380/sq ft across Seattle and the Eastside, $330–$360/sq ft in Tacoma/Pierce, and $330–$355/sq ft in Olympia/Lacey. A 1,000 sq ft DADU therefore lands at $330K–$380K turn-key; a 750 sq ft DADU lands around $255K–$295K. These include design, permits, and site work — not landscaping or solar.
Fixed costs scale poorly. A 400 sq ft studio still needs a full kitchen, a bath, a meter, a sewer tap, an electrical service, a permit set, and a site mobilization. Those line items total ~$100–$130K regardless of size. Spread across 400 sq ft, the $/sqft creeps higher; spread across 1,000+ sq ft, it floors at $330/sq ft.
Go deeper: Read the Five hidden ADU costs that wreck Puget Sound budgets guide
A garage conversion on an existing slab, with the kitchen on the existing plumbing wall, no electrical service upgrade, and no critical-areas review. Real-world floor for a clean conversion is around $120–$170K in 2026 dollars. Below that price-point, you are usually looking at an unpermitted job that will not refinance, will not insure, and will not transfer at sale.
Go deeper: Read the Garage conversion timeline in Puget Sound (2026) guide
Fixed-price (Firm Lump Sum) is our standard contract for 95% of projects. We use cost-plus only for renovation scopes where existing conditions cannot be honestly priced — typically pre-1940 conversions with unknown framing or buried utilities. Even on cost-plus, we set a Guaranteed Maximum Price (GMP) so your downside is capped.
Go deeper: Read the Fixed-price vs time-and-materials: which contract to sign guide
Six common exclusions across the industry: (1) landscaping and irrigation, (2) fencing, (3) decorative hardscape beyond a code path, (4) solar PV, (5) furniture/appliance upgrades beyond a contract allowance, (6) art and window coverings. We list these explicitly in the contract under "Excluded Scope" so there is zero ambiguity. Roughly 70% of clients add 1–3 of these as separate post-CO work.
Go deeper: Read the Five hidden ADU costs that wreck Puget Sound budgets guide
Plan check + building permit fees: $5–12K depending on AHJ and project valuation. SDC/impact fees vary wildly — Seattle waives ADU impact fees under SMC 23.76, Bellevue charges ~$3–7K for water/sewer, Kirkland $4–8K, Tacoma $2–5K. Plan budget of $8–22K total for fees in most Puget Sound cities. We list each fee line in the feasibility report so there are no surprises at permit issuance.
Go deeper: Read the King County side sewer permits for ADUs: cost & timeline (2026) guide
Yes — Fannie Mae HomeStyle Renovation, Freddie Mac CHOICERenovation, FHA 203(k) Standard, and several Washington credit-union renovation loans (BECU, Sound CU, WSECU) underwrite based on as-completed appraised value, not current value. That structure typically funds 90–95% of project cost without a HELOC. Our financing/$citySlug pages walk through each option with current rate ranges.
Go deeper: Read the Seattle ADU financing: 7 loan products compared (2026) guide
Most Puget Sound ADUs do. A 750 sq ft DADU costing $310K with $2,650/mo market rent yields ~$31,800 gross annual / $24,500 NOI. At 5.5% cap rate that is $445K of valuation added. The IRS allows 27.5-year depreciation on the rental portion (Pub 527), and Washington has no state income tax — so federal-only tax on net rent is modest. Full pro-forma on our roi-calculator.
Yes. The county assessor reassesses your parcel under RCW 84.40.0301 the year after final inspection. Typical Seattle increase is ~$2,800–$4,200/year, Bellevue ~$3,400–$5,100, Tacoma ~$1,900–$2,800. We model this exactly on the tax-benefits/$citySlug pages using your county's current levy rate. The ADU's rental income covers the tax increase ~12–18x over.
Go deeper: Read: What an ADU does to your property tax in King County
If your parcel is inside an HOA or CC&R-regulated subdivision, you need written architectural approval before permit. About 25% of Eastside lots are HOA-controlled. We handle the HOA architectural submittal as a fixed-fee add ($1,200) and design to common HOA constraints (roof pitch matching, siding palette, height < primary). HOA review typically adds 4–8 weeks to schedule.
We publish honest cost ranges per city and per size band on the cost/$citySlug and cost-per-sqft/$citySlug/$sizeBand pages — updated quarterly from our actual closed-contract data. We do not publish a single "$X price" because soils, slope, utilities, and AHJ vary enough that a fixed published number would be lying to clients on either the high or low side.
Three honest reasons explain most price gaps: (1) they omit scope (no IECC blower door, no upgraded service, no engineered fill on poor soils); (2) they use unlicensed sub-tier labor (no L&I, no workers' comp — your liability if injured on your lot); (3) they price tight to win and recover with change orders averaging 18–25% of contract. Compare apples to apples on scope, license, and change-order history.
INTERNAL_LINKS / Deep Map
Range pricing is how builders hide cost creep. After feasibility we lock a single number with a written allowance schedule. If we miss a soft cost, we eat it.
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