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ADU contractor: who can legally build one

By the HyreADU research desk. Last checked .

The short answer

An ADU contractor in California is a contractor licensed by the CSLB to build the whole unit. The board says that means a B General Building contractor, or a C-47 contractor for a manufactured home set on site. There is no special “ADU license”, so the B license is the one to look for.

The license that matters

California has no ADU license class. The Contractors State License Board’s own ADU fact sheet tells homeowners to hire a B General Building contractor to build or install an ADU. A C-47 General Manufactured Housing contractor may install one only if it is a manufactured home built off site and delivered.

Specialty trades, such as electricians, plumbers and roofers, hold C licenses. The board says they cannot generally manage a full ADU build, though the main contractor can hire them as subcontractors.

What the contract must contain

An ADU is a home improvement job under state law. That means a written contract. Bus. & Prof. Code § 7159 caps the down payment at $1,000 or 10 percent of the contract price, whichever is less. On a job the size of an ADU, the $1,000 figure is the one that applies.

The contract should also tie each progress payment to finished work, list allowances by name, and say how change orders are priced. Our ADU bid comparison walks through those lines.

How to check one in five minutes

Search the license number on the CSLB site. Check that the status is active, that the class is B (or C-47 for a manufactured unit), and that the name on the license matches the name on your contract.

Then look for the firm’s name on ADU permits in your city. Our permit contractor index shows which firms appear on ADU permits in five California jurisdictions.

What to do next: read the questions to ask an ADU builder, check what decides ADU cost, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.

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Questions

Can a handyman build an ADU?

Not in California. A whole ADU is far past the small-job exemption in the Contractors State License Law, so it needs a licensed contractor. The CSLB names the B General Building license as the one for an ADU.

Is an “ADU company” a different kind of contractor?

No. It is a business model, not a license. An ADU company still needs a B license to build in California. See general contractor vs ADU company.

What deposit can an ADU contractor ask for?

In California, no more than $1,000 or 10 percent of the contract price, whichever is less, under Bus. & Prof. Code § 7159.

Does HyreADU recommend contractors?

No. We publish no ranked list and we have no partner builders. Matching is not live yet. We publish the license and permit record so you can check firms yourself.

Sources

HyreADU is a publisher. It does not design, permit or build ADUs, has no partner builders, and gives no legal, tax or engineering advice. Rules vary by state and city; California rules are labeled as such.