Who can legally build a detached ADU in California?
A new, separate dwelling on your lot — foundation, framing, roof, plumbing, electrical, heating, finishes. New construction, many trades.
Check a specific contractor for this job
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Licensed for this work
A B General Building license covers new residential structures requiring two or more trades — which is what an ADU is. CSLB's own ADU guidance names the B as the license that builds them. (§7057)
Looks like it should cover this — but doesn’t
This is the mismatch to watch for. "Residential Remodeling" sounds like it covers an ADU. It doesn't: a B-2 is limited to improvements to an existing structure and may not do new construction, structural work, or install electrical, plumbing or heating systems. A detached ADU is all of those. (§7057.5)
Licensed for part of it — not the whole job
Specialty contractors may perform their own trade on this job as subcontractors. Any specialty not listed is in the same position.
An A General Engineering license covers site work — grading, drainage, utility trenching — but not the building. (§7056)
Basis: B&P Code §7057; B&P Code §7057.5; B&P Code §7056; CSLB Fast Facts: Building a Residential ADU. A California contractor may only contract for work within their classification (B&P Code §7059), with an exception for work incidental and supplemental to their own trade (16 CCR §831). This page reads the classification rules; it is not legal advice and says nothing about quality of work. Confirm with CSLB before signing.