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 / Services

Our ADU Construction Services

Three ADU types, one team, zero headaches. Every service includes design, permits, and construction — from start to finish.

— Backyard Cottage

Detached ADU (DADU)

A fully independent structure built in your backyard. This is the most popular ADU type in the Puget Sound region — offering maximum privacy, the best rental income potential, and the highest property value increase. We've built over 25 DADUs across King and Pierce County.

400–900 sq ft

$185k–$320k

6–8 month build

Custom or pre-approved plans

Get a Quote for Backyard Cottage →

What's Included

✓ Full architectural design & drawings
✓ Engineering stamps & structural calcs
✓ Site survey & soil testing
✓ All permit applications & city fees
✓ Foundation, framing, roofing
✓ MEP (plumbing, electrical, HVAC)
✓ Interior finishes & fixtures
✓ Landscaping restoration
✓ Final inspection & Certificate of Occupancy

— Transform Your Existing Garage

Garage Conversion

Convert your existing garage into a fully permitted, livable space. This is the fastest and most cost-effective path to ADU ownership. Because you're working with an existing structure, permit timelines are shorter and construction costs are significantly lower than new builds.

400–650 sq ft

$95k–$160k

3–5 month build

Uses existing structure

Get a Quote for Transform Your Existing Garage →

What's Included

✓ Structural assessment of existing garage
✓ Architectural plans for conversion
✓ Permit applications
✓ Structural reinforcement if needed
✓ Insulation & weatherproofing
✓ Full MEP installation
✓ Interior finishes
✓ New windows & entry door
✓ Final inspection & CO

— Multi-Generational Living

Attached / Basement ADU

Add a self-contained living suite to your existing home. Whether it's a basement conversion, above-garage addition, or side-attached unit, this option leverages your existing foundation and structure for significant cost savings. Perfect for aging parents or supplementing your mortgage.

300–700 sq ft

$85k–$180k

4–6 month build

Leverages existing foundation

Get a Quote for Multi-Generational Living →

What's Included

✓ Design integration with existing home
✓ Separate entrance design
✓ Permit applications
✓ Waterproofing (basement)
✓ MEP with separate meter options
✓ Sound insulation between units
✓ Interior finishes
✓ Egress windows & fire safety
✓ Final inspection & CO

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