Seattle, WA · AADU
ATTACHED ADU Builder in Seattle, WA
An attached ADU shares a wall (and often a foundation) with your primary home. We specialize in carving these units out of basements, daylight floors, and underused side wings — all while preserving the existing home's character and avoiding common moisture, sound-isolation, and egress mistakes.
Build timeline
4–5 months
Typical sqft
300–800 sqft
Seattle cost
$185K – $345K
Permit window
12–16 wk
What attached adu looks like in Seattle
ATTACHED ADU projects in Seattle are shaped by local zoning (SF 5000 / NR2 / NR3), a lot minimum of 3,200 sqft, and the kinds of sites we see day-to-day: Ballard, Queen Anne, Capitol Hill. Below is what every Seattle AADU project from Golden State includes — fixed-price, one contract, one warranty.
- ✓Existing-conditions survey
- ✓Egress + life-safety design
- ✓Acoustic + thermal envelope upgrades
- ✓Independent entry construction
- ✓Sub-metering of power & water
- ✓Final inspection + handover
Other services in Seattle
More from Golden State ADU in Seattle
DADU
DETACHED ADU in Seattle
Stand-alone backyard cottages built from the ground up — engineered for rental income, multi-generational living, or your home office.
Garage
GARAGE CONV. in Seattle
Convert an under-used garage into a high-end studio, office, or rental quarter without surrendering your driveway.
Additions
MODERN ADDITIONS in Seattle
Structural expansions for growing families — second stories, primary suites, kitchen extensions. Steel, glass, and Pacific Northwest materials.
GC
GENERAL CONTRACTING in Seattle
Full-service general contracting for remodels, renovations, and ground-up custom homes throughout the Puget Sound region.
Feasibility
FEASIBILITY STUDIES in Seattle
Before you commit, we analyze zoning, lot coverage, setbacks, utilities, and ROI so you have a real number — not a guess.
ATTACHED ADU across the Puget Sound
ATTACHED ADU builders in nearby cities
Start your Seattle AADU feasibility
$1,500 buys lot analysis, Seattle zoning verification, and a fixed price you can build a budget on.
Request Seattle feasibilityFrequently asked
What is included in ATTACHED ADU in Seattle?
Our ATTACHED ADU in Seattle scope includes design through completion: feasibility, schematic design, construction documents, permit submittal and review management, construction with one self-performed framing crew plus L&I-licensed MEP subcontractors, all required WA inspections, certificate of occupancy, and warranty. One contract, one license number, one warranty — not a coordination headache across five vendors.
How is ATTACHED ADU in Seattle different from a generic remodel?
ATTACHED ADU in Seattle carries code, permit, and construction details that a one-off remodeler hasn't repeated enough times to optimize. Examples: IECC R406 envelope path selection, fire separation when units are within 5 ft, side-sewer slope requirements, IRC Appendix AQ when permitted as a tiny house, separate utility metering rules. We do this scope every month — repetition is what makes our first-cycle approval rate and our schedule reliability stand out.
What is the typical price range for ATTACHED ADU in Seattle?
ATTACHED ADU in Seattle pricing in 2026 lands in the $295–$465/sqft all-in range depending on size, lot conditions, finish tier, and AHJ. The wide range is real — small lots with difficult access, soils requiring pier-and-beam, or service upgrades push the upper end; flat lots with good access and a catalog plan land at the lower end. Our feasibility report gives you a ±15% number tailored to your specific lot in two weeks.