What is the difference between an ADU and a DADU?

An ADU (accessory dwelling unit) is a secondary living space attached to or inside your main home, like a basement or garage conversion. A DADU (detached accessory dwelling unit), often called a backyard cottage, is a separate standalone structure on the same lot. Both have a full kitchen, bathroom, and sleeping area, and both can typically be rented out or used for family.

How much does it cost to build a DADU in the Seattle–Tacoma area?

Cost depends on size, site conditions, and finish level, but detached units in the Puget Sound region commonly range from about $250,000 to $450,000 or more. We provide a fixed-price contract after a site evaluation, so your number does not move once the scope is set.

How long does an ADU or DADU project take?

Plan on roughly 10 to 16 months end to end for a detached unit: design and engineering (1 to 3 months), permitting (varies by jurisdiction, often 3 to 6 months), and construction (4 to 7 months). Timelines vary by city and site, and we manage all three phases.

Do I need a permit, and can you handle it?

Yes. ADUs and DADUs require permits, and the rules differ between Seattle, King County, Pierce County, and individual cities. We handle design, engineering, and the full permitting process as part of the contract, so you do not deal with the jurisdiction directly.

Can I rent out my ADU?

In most Puget Sound jurisdictions, yes. ADUs can be rented long term, and many homeowners use them for rental income, multigenerational living, or a home office. Specific rules such as short-term rental limits vary by city, and we confirm what applies to your lot.

What areas do you serve?

We build throughout King County and Pierce County, including Seattle, Tacoma, Bellevue, Renton, Kent, Federal Way, and Puyallup.

Home / Pricing

ADU Pricing

Transparent, fixed-price contracts. No hidden fees, no surprise change orders.

— Investment

Transparent pricing. What you see is what you pay.

These ranges reflect our recent builds. Every project gets a custom quote — we'll give you a number within 48 hours of site visit.

Garage / Basement

Conversion

$85k–$160k

300–650 sq ft · 3–5 months

✓Design & drawings
✓Permit application
✓All city fees
✓Licensed construction
✓MEP (plumbing/electrical/HVAC)
✓Interior finishes
✓Final inspection
–Custom architecture
–Premium finishes
–Smart home pre-wire
–Landscaping
–Priority scheduling

Get Quote

Detached Cottage

$185k–$320k

400–900 sq ft · 5–7 months

✓Design & drawings
✓Permit application
✓All city fees
✓Licensed construction
✓MEP (plumbing/electrical/HVAC)
✓Interior finishes
✓Final inspection
–Custom architecture
–Premium finishes
–Smart home pre-wire
–Landscaping
–Priority scheduling

Get Quote

Large Custom ADU

Premium Custom

$320k+

800–1,200 sq ft · 7–10 months

✓Design & drawings
✓Permit application
✓All city fees
✓Licensed construction
✓MEP (plumbing/electrical/HVAC)
✓Interior finishes
✓Final inspection
✓Custom architecture
✓Premium finishes
✓Smart home pre-wire
✓Landscaping
✓Priority scheduling

Get Quote

ROI Calculator

Estimated Build Cost: $200,000

Expected Monthly Rent: $2,500

$1,700

Monthly Net

9.8 yrs

Payback Period

$100,000

10-Year Gain