Attached ADU in Washington

Explore pre-designed ADU floor plans from Modern ADU Plans — studio, 1-bed, 2-bed, garage conversions & more. Save time, reduce costs & maximize property value with ready-to-build accessory dwelling unit designs.

Bellingham ADU Builders offers full-service ADU construction in Whatcom County, including detached and attached ADUs. Costs range from $200K–$550K+. Permits included. Free 48-hour feasibility study available. HB 1337 allows up to two ADUs per lot.

Lakeside ADU & Home Planning, based in Lake Stevens, WA, is a full-service ADU builder serving the Puget Sound Region. They specialize in backyard cottages, mother-in-law suites, garage conversions, and new builds, managing design, permitting, and construction.

True Built Home builds custom ADUs in Washington & Oregon, offering 14 floor plans from 495–1,199 sq ft, priced from $119,900. Plans include granny flats, in-law suites & backyard cottages with transparent pricing and customizable designs.

Gravity Builders LLC is a licensed ADU contractor and custom home builder in Renton, WA. Specializing in ADU/DADU construction, custom homes, outdoor living spaces, and concrete work, they deliver quality craftsmanship with transparency and integrity.

Seattle's trusted DADU & ADU builder offers custom builds, ADU conversions, and prefab cabins. Transparent pricing, expert guidance, and hands-on construction help homeowners add lasting value with backyard cottages and granny flats.

Emerald ADU Builders Seattle specializes in ADU design, permitting, and construction. They build detached ADUs, attached ADUs, and garage conversions, serving Seattle homeowners with quality craftsmanship and transparent pricing.

Cascadia ADU builds attached, detached, garage & basement ADUs across King, Snohomish, Skagit & Chelan Counties, WA. Full-service design, permitting & construction completed in 8–10 weeks with 10+ years experience.