HiLine Homes is an experienced ADU builder in Idaho with nearly 30 years in custom home construction. They offer attached and detached ADU designs for rental income, multigenerational living, or home offices, with financing options available.
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Zee Design & Build is a Kirkland, WA ADU contractor serving King, Snohomish, Skagit & Island Counties. Offering full-service ADU construction—garage conversions, basement units, backyard cottages & more—since 2012.
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Evola Builds LLC, led by Michael and Amber Evola, offers residential renovation and construction services including bathroom remodels, ADU work, garage conversions, and structural modifications, collaborating closely with architects and homeowners... read more
Twin Brothers Group is a licensed framing contractor in Washington State specializing in ADU, DADU, garage conversions, and home additions across King and Snohomish County, serving Seattle-area GCs and owner-builders.
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Carriage Houses NW is a Pacific Northwest ADU builder specializing in infill housing. They develop ADUs, duplexes, and townhomes, partner with homeowners, and offer fee-to-build services, leveraging WA State HB 1110 and HB 1337 legislation.
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Harjo Construction builds AADUs & DADUs in Seattle with 300+ projects since 2010. Costs range $275K–$650K, max 1,000 sq ft, 4–6 month build time. Seattle removed owner-occupancy rules, boosting ADU rental potential.
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Seattle Modern Buildings ADU Builder is a Seattle-based design-build firm specializing in detached ADUs, duplexes, and modern homes. With deep knowledge of Seattle permitting, zoning, and construction best practices, we help homeowners unlock thei... read more
Marksymov Brownstone LLC is a licensed Seattle ADU contractor offering basement, garage & attic conversions. They handle design, permits & construction, ensuring code compliance across Seattle, Bellevue & Kirkland.
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FTS Excavation offers full-service ADU site development in South Puget Sound, Western Washington. Services include grading, utilities, septic systems, foundation excavation & permits. Certified, reliable ADU contractor for backyard homes &... read more
Our team specializes in ADU construction and home remodeling, creating functional, well-designed spaces with quality craftsmanship and attention to detail.
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The Home Boys is Washington State's largest manufactured home dealer, offering factory-direct pricing across WA, ID, OR, MT, and AK. They carry brands like Goldenwest, Marlette, Clayton, and Cavco, plus ADU-friendly park models under 1,200 sq ft.<... read more
Better Builders is a Seattle-based general contractor specializing in residential remodeling, garage conversions, ADUs, kitchen and bathroom remodels, basement finishing, deck repairs, and exterior work, with dedicated project management.
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Cast Architecture specializes in ADU and backyard cottage design in Seattle since 2009. With 80+ projects, their Cedar Cottage is pre-approved by Seattle & Kirkland. Award-winning designs include Widner Cottage and Lichtenstein Studio. Visit c... read more
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.
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.
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:
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).
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.