Choosing the right contractor is one of the most important decisions you'll make during your ADU project. The builder you hire will directly affect your costs, timeline, quality, and overall experience. Before you sign any contract, make sure you've asked these five essential questions.
1. Are You Licensed, Bonded, and Insured in Washington State?
This is non-negotiable. In Washington state, all contractors performing work over $800 must be registered with the Department of Labor & Industries (L&I) and carry a contractor's license, surety bond, and liability insurance.
Ask for the contractor's license number and verify it at verify.lni.wa.gov. This free lookup tool shows whether the license is active, the bond status, insurance coverage, and whether any complaints have been filed. You should also confirm they carry general liability insurance (at least $1 million per occurrence) and workers' compensation coverage for their crew.
A contractor who hesitates to share this information or tells you "don't worry about it" is a red flag. Walk away. Hiring an unlicensed contractor exposes you to significant legal and financial risk if something goes wrong during construction.
2. What Is Your Realistic Timeline for This Project?
ADU projects in the Puget Sound area typically take 8 to 16 months from permit application to move-in, depending on the type and complexity. That includes permitting (3 to 8 months), construction (4 to 8 months), and final inspections.
When discussing timelines, ask the builder to break it down into phases:
- How long will permitting take, and who manages the permit process?
- When can construction begin after permits are issued?
- What is the expected construction duration?
- How do you handle weather delays or material shortages?
Be cautious of builders who quote unusually fast timelines. An experienced ADU builder will give you an honest range rather than an optimistic promise. Also ask how many projects they run simultaneously. A builder juggling too many jobs may struggle to keep yours on schedule.
3. Can You Provide a Detailed Cost Breakdown?
A trustworthy builder will provide a clear, itemized estimate rather than a single lump-sum number. The estimate should break down costs into categories like:
- Site preparation and foundation
- Framing and structural work
- Roofing and exterior finishes
- Plumbing, electrical, and HVAC
- Interior finishes (flooring, cabinets, fixtures)
- Permit fees and design costs
- Utility connections
Ask specifically about what's included and what's not. Some builders quote a base price that excludes site prep, utility connections, landscaping, or permit fees. Others include everything in a turnkey price. Understanding what you're comparing is critical when evaluating multiple bids.
Also ask about their change order process. Changes during construction are common, and you need to know how they'll be priced and approved. A good builder will have a clear, written process for handling changes.
4. Can You Share Past ADU Projects and Client References?
Experience matters in ADU construction. The permitting process, design constraints, and construction logistics of ADUs are different from general residential construction. Ask specifically about:
- How many ADUs they've completed in the past two years
- Photos or a portfolio of completed projects
- At least three references from recent ADU clients
- Whether any of their projects are available for you to visit in person
When you contact references, ask about the overall experience, not just the finished product. Were they responsive to calls and emails? Did they stay on budget? How did they handle problems that came up? Would the client hire them again?
If a builder can't provide ADU-specific references, that's a sign they may be new to this type of project. That's not necessarily disqualifying, but you should weigh it against other factors like their overall experience and price.
5. How Do You Handle Permitting and Local Regulations?
ADU permitting in the Puget Sound can be complex, with different rules in Seattle, Tacoma, Bellevue, Kirkland, and other jurisdictions. An experienced ADU builder should be fluent in local codes and able to navigate the process efficiently.
Ask them:
- Do you manage the full permitting process, or do I need to hire a separate permit expediter?
- Have you worked with Seattle SDCI (or the relevant local jurisdiction) before?
- Are you familiar with pre-approved ADU plans, and do you recommend them?
- How do you handle design review if it's triggered?
A builder who includes permitting management as part of their service saves you significant time and stress. Builders who have established relationships with local plan reviewers can often anticipate common issues and submit cleaner applications, reducing the back-and-forth that extends timelines.
The Bottom Line
Building an ADU is a significant investment, and the contractor you choose is the single biggest factor in whether the project goes smoothly. Take the time to ask these questions, verify the answers, and compare at least three builders before making your decision. A good builder will welcome these questions because they know transparency builds trust.