1. Check the license
Look up every builder on the Contractors State License Board's license check. It shows whether the license is active, its classification (a new ADU is usually built under a B, general building, license), workers' compensation and bond information, and any public complaints or actions. Make sure the name and license number match the contract.
2. See their finished work
Ask for the addresses of ADUs they have finished, preferably nearby. You can look them up on our map to confirm permits were issued, and for Los Angeles, whether the city signed the unit off as finished. Call past clients and ask about schedule, budget and how problems were handled.
3. Get at least three written quotes
Compare the same scope: design and engineering, permits and fees, foundation, utilities, site work and finishes. A quote far below the others often means something is missing.
For context, Los Angeles permits issued in 2025 declared a median of $50,000 for garage conversions and $109,482 for detached ADUs. Declared values understate real cost; see what an ADU costs.
4. Read the contract before you pay
- Down payment: in California, the down payment on a home improvement contract cannot be more than $1,000 or 10% of the contract price, whichever is less, and later payments cannot get ahead of the work done (CSLB).
- Schedule and payments: tie each payment to finished work you can see.
- Permits: the contract should say who applies for the permit and that the work will be inspected and signed off.
- Changes: changes should be written change orders with prices.
Red flags
- Asks for a large payment or cash up front.
- Suggests skipping permits or inspections.
- Won't give a license number, or the license is inactive or in another name.
- Pressure to sign today.
About builders on this site
Some pages show a featured builder. Those listings are paid and labeled “Sponsored”. We check that a builder holds an active California license when listed, but we don't endorse or guarantee any builder; do the checks above yourself.
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