Pacific Homes Direct in Woodland, WA offers customizable ADUs starting at $49,999. Serving Western Washington and Oregon, they provide granny flats, in-law suites, and backyard cottages with full-service support and factory warranty included.

Brutsky Builds

800 Bellevue Way Northeast, Bellevue, WA 98004

Licensed Eco-Friendly

Brutsky Builds is a licensed ADU contractor in Bellevue offering full-service accessory dwelling unit construction. Services start from $210,000, covering design, permitting, and build completion in ~6 months.

Northwest ADU

1201 Pacific Avenue, Tacoma, WA 98402

Licensed

Northwest ADU is a full-service ADU contractor in Western Washington specializing in detached ADUs, garage conversions, and basement conversions. Serving Pierce, King, and Snohomish Counties, projects range from $180K–$350K+, taking 6–10 month... read more

BB Builders Pro

801 Southwest 16th Street, Renton, WA 98057

Eco-Friendly

BB Builders Pro specializes in ADU construction, garage conversions, home additions, and detached backyard cottages. Services include custom design, permitting, zoning compliance, and renovations—ideal for rental income or family housing.

Sockeye Homes

14638 SE 229th Pl, Kent, WA 98042

Sockeye Homes designs & builds custom ADUs and DADUs, offering full-service support from permits to construction. Fixed-cost packages range from $218K–$335K+, suiting retirees, families & rental income seekers.

Home Care Contractors

10634 East Riverside Drive, Bothell, WA 98011

Luxury Builds

Home Care Contractors builds ADUs in King County, including DADUs, garage conversions, and basement units. They handle permits, design, and construction. Costs range from $300K–$700K, with timelines of 7–13 months total.

Top Volk Construction

204 111th Avenue Northeast, Bellevue, WA 98004

Licensed

Top Volk Construction builds ADUs in the Seattle area, including detached backyard cottages, attached units, garage conversions, and basement ADUs. This licensed contractor manages design, permitting, construction, and inspections for homeowners s... read more

RG ProBuilders

21211 Northeast 72nd Avenue, Battle Ground, WA 98604

For more than 15 years, we’ve turned backyards into beautifully crafted living spaces. From permits to finishing touches, our team knows every step inside and out. Choose the classic charm of our Traditional Series, the clean lines of our Modern... read more

New Image Construction Management

8305 Dallas Avenue South, Seattle, WA 98108

New Image Construction Management is a Washington State general contractor and building company based in Seattle, WA. With a primary focus of new home construction and renovation of residential and commercial properties.

Homez Remodel

13213 Southeast 278th Street, Kent, WA 98042

Licensed 10 years in business Eco-Friendly

Homez Remodel is a Seattle ADU builder specializing in DADUs, backyard cottages, garage conversions & basement ADUs. With 10+ years experience, they handle permits, design & construction across Seattle, Bellevue, Kirkland & more.

Northwest ADU Builders of Mill Creek

6100 219th Street Southwest, Mountlake Terrace, WA 98043

Northwest ADU is a trusted ADU builder in Mill Creek, WA, offering full-service accessory dwelling unit construction, including detached ADUs, garage conversions, and basement conversions, with expert permit and zoning support.

NorthLight Custom Builders

9800 Harbour Place, Mukilteo, WA 98275

Licensed

NorthLight Custom Builders offers ADU construction in King & Snohomish County. Services include attached & detached units for rental income, family living, or home offices. Structured process from consultation to one-year warranty follow-u... read more

Microhouse

114 North 42nd Street, Seattle, WA 98103

Microhouse is a Seattle-based ADU builder specializing in custom detached ADUs (DADUs). They guide homeowners through zoning, design, and construction. Seattle permitted 551 DADUs in 2022, with a 40% increase in 2023. Microhouse offers site assess... read more

Model Remodel

1111 West Nickerson Street, Seattle, WA 98119

Seattle's 2019 ADU law changes made it easier to build accessory dwelling units on single-family lots. DADUs can't exceed 50% of the main home's size. No parking required. New detached ADUs start around $350,000.

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What you need to know

ADU Contractors in Washington State: Navigating a Progressive Housing Landscape

Washington State has become one of the most ADU-friendly states in the nation, largely due to landmark legislation passed in recent years. In 2023, Washington enacted House Bill 1337, which significantly expanded ADU rights across the state. This law requires cities and counties to allow at least two ADUs per single-family lot, prohibits owner-occupancy requirements, and eliminates many restrictive parking mandates. For homeowners and ADU contractors in Washington, this legislation opened up tremendous opportunities to add accessory dwelling units to residential properties throughout the state.

What Washington ADU Contractors Must Know About Local Regulations

While HB 1337 sets a statewide baseline, experienced ADU contractors in Washington State must still navigate local building codes and permitting processes that vary by jurisdiction. Cities like Seattle, Bellevue, Tacoma, and Spokane each maintain their own specific requirements regarding setbacks, height limits, and design standards. For example, Seattle allows ADUs up to 1,000 square feet for detached units and has its own streamlined permitting process. A knowledgeable Washington ADU contractor will be well-versed in these local nuances to ensure your project moves forward without costly delays.

Types of ADUs Built by Washington Contractors

Professional ADU builders in Washington are experienced in constructing a wide variety of accessory dwelling unit types to suit different property layouts and homeowner needs. Common ADU types include:

Detached ADUs (DADUs): Standalone structures built in the backyard, often called backyard cottages
Attached ADUs: Units connected to the primary home, sharing at least one wall
Garage Conversion ADUs: Transforming existing garages into livable dwelling units
Basement ADUs: Converting below-grade spaces into fully functional apartments
Junior ADUs (JADUs): Smaller units created within the existing footprint of a home

Key Considerations When Hiring an ADU Contractor in Washington

Choosing the right ADU contractor in Washington is critical to the success of your project. Washington State requires all general contractors to be licensed through the Washington State Department of Labor & Industries (L&I). Always verify your contractor holds a valid L&I license and carries proper liability insurance and workers' compensation coverage. Look for contractors with demonstrated experience in ADU construction specifically, as these projects involve unique challenges including utility connections, zoning compliance, and energy code requirements under the Washington State Energy Code (WSEC).

The Benefits of Building an ADU in Washington

Investing in an ADU with a qualified Washington contractor offers significant long-term advantages. Homeowners can generate rental income to offset mortgage costs, provide housing for aging family members, or increase overall property value. With Washington's high housing demand, particularly in the Puget Sound region, ADUs represent a smart and increasingly accessible investment. Working with an experienced, licensed ADU contractor in Washington State ensures your project is completed safely, legally, and to the highest standards.

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With over 1995 ADU Contractors in 50 US states - Top ADU Pros attempts to get you into contact with the best ADU Contractors near you.

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