The right ADU contractor holds an active California license, carries insurance, and has built ADUs, not just remodels. Check the license for free on the CSLB website, ask the 15 questions below, and don’t pay a down payment above California’s legal limit of 10% or $1,000, whichever is less.
An ADU is a six-figure project with zoning, utilities, permits, and inspections. Here’s how to vet a builder before you sign.
What should you verify before anything else?
- License. Look up the license on the CSLB website. Confirm it’s active, in good standing, and in a fitting class. A B (General Building) license is the usual class for building an ADU.
- Insurance. Ask for proof of general liability and workers’ compensation. If a worker is hurt on your property and there’s no coverage, you can be exposed.
- ADU experience. Ask how many ADUs they’ve finished in the City of Santa Clarita or LA County in the last two years.
If a contractor can’t clear these three, stop there.
What 15 questions should you ask an ADU contractor?
Experience and process
- How many ADUs have you completed in the last two years, and can I see photos or visit one?
- Have you permitted ADUs with the City of Santa Clarita or LA County?
- Do you handle the permit process, or is that on me?
- What is your realistic timeline from signed contract to final inspection?
Costs and contract
- Is this a fixed-price bid or cost-plus? What exactly is included and excluded?
- What is the payment schedule, and is each payment tied to completed work?
- How do you price and document change orders?
- What allowances are in the bid for finishes and fixtures, and what happens if I go over?
Team and accountability
- Do you use your own crew or subcontractors? Who supervises day to day?
- Who is my point of contact, and how often will I get updates?
- What warranty do you give on workmanship, and for how long?
ADU-specific
- How will you handle utilities, such as a panel upgrade, sewer or septic, and water service?
- Does my main house have fire sprinklers, and is sprinkler work in your bid if it’s needed?
- Can you give me three recent ADU clients I can call?
- What happens if the project runs past the completion date in the contract?
How much can an ADU contractor ask for up front?
For home improvement contracts, California caps the down payment at 10% of the contract price or $1,000, whichever is less. After that, payments should follow completed work. A contractor asking for a large deposit “for materials” is a warning sign. See ADU contractor red flags for more.
What should a good ADU contract include?
A solid California home improvement contract spells out:
- The full scope of work, with materials and allowances
- The total price and a payment schedule tied to milestones
- Start and completion dates
- How change orders are requested, priced, and approved
- Warranty terms
- The contractor’s name, address, and license number
If something is only verbal, assume it isn’t in the deal.
Should you hire a design-build firm or a general contractor?
A design-build firm handles design, permits, and construction under one contract. A general contractor builds from plans you or an architect provide. Design-build is usually simpler for a first ADU. See design-build vs. general contractor for the trade-offs.
Want a local ADU contractor to start with?
Call (661) 486-8393. If no one answers, leave a voicemail with your name, phone number, address, and the type of ADU you want. You can also use the contact form. We’ll pass your details to a local ADU contractor, who will follow up with you directly. There’s no obligation to hire, and you should still check their license on the CSLB website.
ADU contractor FAQs
What license does an ADU contractor need in California?
A contractor building a new ADU typically holds a B (General Building) license from the CSLB. Specialty trades, such as fire sprinklers (C-16), have their own license classes.
How many bids should I get?
Getting more than one bid helps you spot missing scope and unusual prices. Compare bids line by line, especially what each one excludes.
Who pulls the ADU permit?
Usually the licensed contractor. If someone asks you to pull the permit as an owner-builder while they do the work, you take on legal responsibility for the project. Treat that as a red flag.
How do I check a contractor’s complaint history?
Start with the license lookup on the CSLB website, which shows license status and any public disciplinary actions. Then search the business name with words like “complaint” or “lawsuit” and call references.