Hiring the wrong ADU contractor can turn what should be an exciting project into a costly, stressful mess. With accessory dwelling units running anywhere from $150,000 to $400,000 in California, you can’t afford to get this decision wrong. The contractor you choose will determine whether your build stays on budget, on schedule, and up to code.
What Should I Ask My ADU Contractor
The tricky part? Most homeowners have never built an ADU before. You don’t know what you don’t know. And that’s exactly how bad contractors slip through the cracks. Asking the right questions upfront separates a smooth, stress-free build from a nightmare that drains your wallet and patience.
Here are 10 questions every California homeowner should ask before signing on the dotted line.
1. How Many ADUs Have You Actually Built?
This is the single most important question, and it should be the first one out of your mouth. General construction experience and ADU-specific experience are two very different things.
ADU projects come with their own set of challenges. California has unique zoning laws, setback requirements, and building codes that apply specifically to accessory dwelling units. A contractor who has built 50 kitchens but zero ADUs may not understand how to navigate city permitting, utility hookups, or the latest state regulations like AB 2221 or SB 9.
Ask for a specific number. If they hesitate or give you a vague answer like “we’ve done plenty,” that tells you something.
2. Can You Show Me Completed ADU Projects?
Talk is cheap. You want proof.
A reputable ADU contractor should have a portfolio of finished projects they’re proud to show off. Ask to see photos, and if possible, visit a completed ADU in person. Pay attention to these details:
- Quality of finishes like cabinetry, flooring, and fixtures
- How well the ADU blends with the main home and surrounding property
- Space utilization and whether the layout feels practical
- Overall craftsmanship in trim work, paint, and exterior details
At Nestadu, we encourage every potential client to review our past work because we believe our craftsmanship speaks louder than any sales pitch.
3. Are You Licensed, Bonded, and Insured in California?
This one is non-negotiable. In California, any contractor handling a project over $500 must hold a valid license from the Contractors State License Board (CSLB). But don’t just take their word for it.
- Ask for their CSLB license number
- Verify it yourself at the CSLB website (cslb.ca.gov)
- Confirm their insurance covers general liability and workers’ compensation
- Check that the license is active and has no complaints filed against it
A licensed, bonded, and insured contractor protects you from financial liability if something goes wrong on your property during construction. Skipping this step is a risk that’s simply not worth taking.
4. Do You Handle Permits and Local Zoning Compliance?
ADU permitting in California is not a simple process. Every city and county has its own rules on top of state-level regulations. Your contractor needs to know setback requirements, height restrictions, lot coverage limits, and utility connection rules specific to your area.
Some contractors only handle the build and leave the permitting headache to you. That’s a red flag. A full-service ADU builder like Nestadu manages the entire process, from pulling permits to scheduling inspections, so you don’t have to chase down paperwork at city hall.
Ask specifically: “Will you handle all permits and inspections, or is that on me?”
5. What’s Your Realistic Timeline for My Project?
Most ADU projects in California take anywhere from 8 to 14 months when you factor in design, permitting, and construction. But timelines vary widely depending on your city’s permitting speed, project complexity, and the contractor’s workload.
Here’s what you should dig into:
- How long is the design and permitting phase? Some cities take 6 to 12 weeks just for plan review.
- What’s the estimated construction duration? A typical detached ADU build runs 4 to 6 months.
- How many projects are they juggling simultaneously? If they’re overbooked, your project could sit idle for weeks.
- What’s their plan for handling delays? Weather, material shortages, and inspection failures happen. You want a contractor with a backup plan.
Get the timeline in writing. Verbal promises mean nothing when you’re six months in and still staring at a half-finished structure.
6. Can You Provide a Detailed Written Estimate?
A vague quote that says “around $250K” should make you nervous. You need a line-by-line breakdown that covers every major cost category.
Your written estimate should clearly include:
- Design and architectural fees
- Permit and inspection costs
- Site preparation and foundation work
- Framing, electrical, plumbing, and HVAC
- Interior finishes (flooring, cabinets, countertops, fixtures)
- Exterior work (siding, roofing, landscaping restoration)
- Contingency allowance for unexpected issues
Transparent pricing is a hallmark of a trustworthy ADU builder. At Nestadu, we provide clear, itemized estimates so homeowners know exactly where their money is going before construction begins.
7. How Do You Handle Change Orders and Unexpected Costs?
Here’s a reality check: almost every construction project hits a surprise or two. Maybe your soil conditions require deeper footings. Maybe you decide mid-build that you want upgraded kitchen countertops. These changes cost money.
The key question is how your contractor communicates and documents these changes. A good contractor will present any cost change in writing, explain why it’s needed, and get your approval before proceeding. A bad one will tack on charges at the end and hope you don’t notice.
Ask them directly: “What’s your process when something unexpected comes up that affects the budget?”
8. What’s Your Payment Structure?
How a contractor handles payments tells you a lot about how they run their business.
Healthy payment structures typically look like this:
- A small deposit upfront (10-15% is reasonable)
- Milestone-based payments tied to completed phases (foundation, framing, rough-ins, finishes)
- Final payment upon project completion and your approval
Red flags to watch for:
- Demanding 50% or more upfront before any work starts
- No written payment schedule in the contract
- Pressure to pay in cash with no receipts
Never pay for work that hasn’t been completed. Period.
9. Will I Have a Dedicated Point of Contact?
ADU builds can stretch over many months. During that time, you’ll have questions, concerns, and decisions to make. You need to know exactly who to call.
Ask your contractor whether you’ll be assigned a dedicated project manager. Find out how often you’ll receive progress updates and whether they prefer phone calls, emails, or a project management app. The best ADU contractors keep communication consistent and proactive, so you never feel left in the dark about what’s happening on your property.
Nestadu’s team prioritizes clear communication throughout every phase, because we’ve seen firsthand how much smoother a project runs when homeowners feel informed and involved.
10. What Warranties Do You Offer After the Build?
Your relationship with your ADU contractor shouldn’t end the day they hand you the keys. Quality builders stand behind their work with clear warranty coverage.
Ask about:
- Structural warranty covering the foundation, framing, and roof
- Workmanship warranty for finishes, installations, and general build quality
- Manufacturer warranties on appliances, fixtures, and materials
- How to file a warranty claim if something needs attention after move-in
Get every warranty detail in writing before you sign the contract.
Red Flags That Should Make You Walk Away
Beyond asking the right questions, keep your eyes open for these warning signs:
- No CSLB license or expired insurance. Walk away immediately.
- Refuses to provide references or a portfolio. If they can’t show past work, there might not be any worth showing.
- No written contract. A handshake deal on a six-figure project is a recipe for disaster.
- Pressure to sign quickly. A confident contractor gives you space to make a decision.
- Lowball estimates that sound too good. If one bid is dramatically cheaper than every other quote, something is missing.
Finding the Right ADU Builder in California
Choosing an ADU contractor is about more than just comparing prices. It’s about finding a team that understands California’s ADU landscape, communicates honestly, and delivers results you’ll be proud of for years to come.
At Nestadu, our experienced team of ADU contractors and designers handles every step, from initial concept and design to permits, construction, and final inspection. We believe in transparent pricing, meticulous craftsmanship, and making the entire process as simple as possible for homeowners across California.
If you’re thinking about building an ADU, start by asking these 10 questions to every contractor you interview. And when you’re ready to work with a team that welcomes every single one of them, reach out to Nestadu for a free consultation. We’d love to help bring your vision to life.