Mountlake Terrace, WA · AADU
ATTACHED ADU Builder in Mountlake Terrace, 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
Mountlake Terrace cost
$170K – $317K
Permit window
8–12 wk
What attached adu looks like in Mountlake Terrace
ATTACHED ADU projects in Mountlake Terrace are shaped by local zoning (RS-7.2 / RS-8.4), a lot minimum of 7,200 sqft, and the kinds of sites we see day-to-day: Town Center, Lake Ballinger, Cedar Way. Below is what every Mountlake Terrace 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 Mountlake Terrace
More from Golden State ADU in Mountlake Terrace
DADU
DETACHED ADU in Mountlake Terrace
Stand-alone backyard cottages built from the ground up — engineered for rental income, multi-generational living, or your home office.
Garage
GARAGE CONV. in Mountlake Terrace
Convert an under-used garage into a high-end studio, office, or rental quarter without surrendering your driveway.
Additions
MODERN ADDITIONS in Mountlake Terrace
Structural expansions for growing families — second stories, primary suites, kitchen extensions. Steel, glass, and Pacific Northwest materials.
GC
GENERAL CONTRACTING in Mountlake Terrace
Full-service general contracting for remodels, renovations, and ground-up custom homes throughout the Puget Sound region.
Feasibility
FEASIBILITY STUDIES in Mountlake Terrace
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 Mountlake Terrace AADU feasibility
$1,500 buys lot analysis, Mountlake Terrace zoning verification, and a fixed price you can build a budget on.
Request Mountlake Terrace feasibilityFrequently asked
What is included in ATTACHED ADU in Mountlake Terrace?
Our ATTACHED ADU in Mountlake Terrace 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 Mountlake Terrace different from a generic remodel?
ATTACHED ADU in Mountlake Terrace 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 Mountlake Terrace?
ATTACHED ADU in Mountlake Terrace 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.