DADU and ADU Builders in Seattle
Seattle calls a backyard cottage a DADU, and it has more contractors who build nothing else than any city outside California. State law HB 1337 and the city's 2025 code update allow two accessory units per lot, drop the owner-occupancy rule, and let a DADU be subdivided and sold with its own title, which turns a backyard build into something you can separate later. The city publishes pre-approved DADU plans too. This page covers builders and design-build firms working Seattle, the Eastside, Tacoma and the wider Puget Sound. We rank on DADU volume, whether they build the pre-approved plans, and how they handle drainage, tree ordinances and tight side-yard access.
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Award-winning Olympia design-build firm specializing in ADUs, tiny homes, and custom residential construction with a collaborative builder co-op model and focus on eco-friendly, innovative design.
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Bainbridge Island-based design-build firm specializing in sustainable ADUs, tiny homes, and residential construction with 20 years of experience and LEED expertise.
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Tumwater-based general contractor offering detached and attached ADU construction, garage conversions, and tiny home builds across Olympia, Tumwater, and Puget Sound communities.
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Seattle ADU specialist with 150+ completed units since 2012. Energy Star certified, BBB A+ rated, and award-winning builder of detached and attached ADUs across the Puget Sound region, from the initial feasibility through final delivery.
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General contractor with 25 years of Pacific Northwest experience, serving Gig Harbor and the wider Puget Sound region with site-built ADU construction, custom homes, and renovation work.
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Urban Builder LLC is a family-owned contractor specializing in ADU and DADU construction, with 200+ completed projects and a father-and-son engineering background.
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DADU PRO specializes in designing and building detached accessory dwelling units with eight pre-approved floor plans and comprehensive support from architect, engineer, permitting, and construction.
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Custom ADU builder in Seattle led by Aharon Ben Elisha, a working Pacific Northwest carpenter since 2006. Handles design, permits, and full construction of detached and attached ADUs across King, Snohomish, and Pierce counties.
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Dream DADU designs, finances, and builds detached accessory dwelling units for Bellevue homeowners, offering an integrated service that includes flexible financing options and a simplified permitting process.
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Women-owned Seattle ADU builder serving Western Washington. Handles full-service construction from feasibility and design through permitting and on-site building of detached and attached accessory dwelling units.
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Emerald City Construction is a Redmond-based builder with 17+ years of experience and a BBB A+ rating, specializing in King County DADU construction and custom home remodels.
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Seattle remodeling firm founded in 2010 with 12 Master Builders Association excellence awards. Builds ADUs, detached cottages, and backyard units alongside whole-home remodels, kitchens, and additions across Seattle and the Puget Sound.
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Olympia-based general contractor with 25 years of experience in residential construction, custom builds, renovations, and ADU projects serving the South Puget Sound region.
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Haas Development and Construction operates a Seattle-based builder and cabinetry shop, offering DADU construction with prefab plans pre-approved by the City of Seattle and full design-to-occupancy coordination.
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A Seattle-based design-build firm creating ADUs that match the character of existing homes and neighborhoods. Handles full renovation and new construction services alongside ADU work.
Frequently asked questions
What is the difference between an ADU and a DADU in Seattle?
Seattle uses the term DADU to refer to a detached accessory dwelling unit, which is essentially a backyard cottage. Most builders in this directory offer both attached and detached options to suit your lot requirements.
Can I build more than one accessory unit on my property?
Yes. Recent state law HB 1337 and the 2025 city code updates allow for two accessory units per lot. You're also no longer required to meet the owner-occupancy rule to build them.
Are there builders who can help with the entire process from design to permits?
Many of the listed professionals provide full-service support. This includes everything from initial feasibility studies and architectural design to engineering, permitting, and final construction.
Can a DADU be sold separately from my main house?
New regulations allow a DADU to be subdivided and sold with its own separate title. This makes them a viable long-term investment or a way to create independent property assets.
Do some contractors offer specialized floor plans to speed up the process?
Some specialists in the region offer pre-approved floor plans to streamline the design and permitting phases. This can be a helpful way to simplify the construction of a detached unit.