Planning guide

How to Choose an ADU Builder in Seattle

You have already decided to build an ADU or DADU. The zoning works, the lot has room, and you know why you want it, whether that is rental income, space for family, or a home office separate from the main house. What is left is the harder decision: which builder gets the job.

Most guides on this stop at licensing and insurance. Those matter, and you should verify a builder's Washington State contractor license directly through the L&I verification tool before you sign anything. But by the time you are comparing two or three builders who all have clean licenses and reasonable references, the checklist stops helping. What separates them is how they structure the work, what their warranty actually covers, and whether their track record holds up when you look closely.

Design-Build or General Contractor: Decide This First

Before you compare bids, decide which delivery model you want, because it changes what you are actually comparing.

A design-build firm handles design and construction under one contract and one team. The people who draw the plans talk to the people who build them, every week, because they work for the same company. Budgets tend to firm up earlier, often as a fixed price set before construction starts, since the same team that designed the ADU is the one pricing it. If something goes wrong, there is one company to hold accountable, not a design mistake pointing at a contractor and a contractor pointing at the drawings.

A general-contractor-only arrangement means you or a separately hired architect finish the design first, then take those finished plans out to bid. This gives you more control over who does the design work and lets you shop the construction price competitively once plans are locked. It also means you are the one coordinating between the architect and the builder if a detail does not translate cleanly from paper to framing, and final cost is less certain until bids come back, since pricing usually runs closer to cost-plus than fixed-price.

Neither is wrong. If you want one team, earlier cost certainty, and a single point of accountability, design-build usually fits better. If you already have plans you like, or you want to run a competitive bid and stay closely involved in decisions, general-contractor-only can make more sense. What matters is asking every builder you talk to which model they are offering, because "we handle everything" means something different at a design-build firm than it does at a contractor who plans to hand you off to an architect first.

Love Construction works ADU and DADU projects in SeaTac and the greater Seattle area, alongside Passive House builds and full remodels. Whichever builder you choose, ask them directly which of these two models you are getting, and get the answer in writing before you sign.

Ask What the Warranty Actually Adds

A written warranty is not the whole picture in Washington, and a short one is not necessarily a red flag by itself, but you should know what baseline protection already exists before you judge what a builder is offering on top of it.

Washington law gives homeowners a six-year window to bring a construction defect claim, running from substantial completion of the project (RCW 4.16.310). In 2022, the Washington Supreme Court ruled in Tadych v. Noble Ridge Construction that a builder's attempt to shrink that window to one year through a boilerplate warranty clause was unenforceable, specifically because it stripped the homeowner of that six-year right without giving them anything in return. The court did not set a new minimum warranty length, but the ruling put builders on notice that a short warranty buried in the contract, offered with no benefit to the homeowner, is now easier to challenge.

That means a builder's written warranty should be read as an addition to your legal protection, not a substitute for it. When you compare builders, ask what their warranty actually covers: response time when something fails after you move in, whether it covers materials, labor, or both, and who specifically you call. A vague answer, or a warranty that only exists because a template said to include one, tells you more than the number of years printed on it.

Read Reviews Like You Are Checking a Reference, Not Skimming Stars

Anyone can collect five-star reviews. Fewer builders can produce reviews that hold up when you read them closely.

Look past the star rating to the content. A genuine review usually names the project type, mentions a rough timeline, and sometimes names a crew member or project manager. Reviews that repeat the same generic praise, "great work, highly recommend," across a dozen entries with no specifics are worth discounting, especially if several of them landed within days of each other. Middle-of-the-road reviews, the three- and four-star ones, are often the most useful, because they describe what went right and what did not without either extreme.

Check the reviewer, not just the review. A profile with a single review for a single company is a weaker signal than one with a history of reviewing several different businesses. And pay attention to how a builder responds to a negative review. A defensive or dismissive reply tells you how they will likely respond if something goes wrong on your project.

The same scrutiny applies to a portfolio. A builder whose photos are mostly kitchens and bathrooms with one or two ADUs mixed in is a different hire than one whose recent, dated project history is dominated by ADU and DADU work specifically. Ask when each photographed project was completed and whether it was in Seattle proper or a different jurisdiction. Permitting and code details differ enough between cities that experience two counties over does not always transfer directly.

Test Their Knowledge of Seattle's Specific ADU Rules

A builder who specializes in ADUs should be able to talk through Seattle's rules from memory, not look them up while you are on the phone. Seattle allows up to two accessory dwelling units per qualifying lot, one attached and one detached, with no owner-occupancy requirement and no off-street parking mandate. A detached ADU has to meet the city's size, height, and setback rules, and a builder who has done this work before should be able to sketch roughly what fits on your lot before a formal design even starts.

Permitting is the other test. Seattle's Department of Construction and Inspections requires a construction permit for a detached ADU, covering structural, mechanical, electrical, energy, and land use review. Projects using a pre-approved design from the city's ADUniverse program can often clear permit review in two to six weeks; a fully custom design takes meaningfully longer. Ask which path your builder is planning to use and why, and ask them to be specific about the current review timeline rather than quoting a number that sounds good in a sales conversation.

The Short Version

Verify the license. Check the insurance. Then go further: settle whether you want a design-build team or a general contractor working from finished plans, find out what the warranty adds beyond your legal rights under Washington law, read reviews for specifics instead of stars, and ask the builder to prove they know Seattle's ADU rules well enough to explain them without a script. Those are the questions that separate a builder who does occasional ADU work from one who actually specializes in it.