ADUs · California Law
Your city has to offer pre-approved ADU plans now
A state law that took effect in January 2025 changed the ADU permitting math, and most homeowners — and a fair number of builders — still don't know it exists.
Under AB 1332 (Government Code §65852.27), every California city and county — charter cities included — must run a pre-approved ADU plan program, must not restrict who is allowed to submit plans, and must approve or deny a qualifying application within 30 days.
What the law requires
- Every city and county must have a program. This includes charter cities, which are often exempt from state housing mandates. Not here.
- Cities cannot restrict who submits plans for pre-approval.
- A 30-day ministerial clock. An application using a pre-approved plan must be approved or denied within 30 days. Ministerial means it is checked against objective standards — there is no discretionary design review to get lost inside.
- Cities must publish the approved plans on their website, along with the contact information of whoever submitted them.
What it changes for your project
Timeline
The difference is between a plan-check process measured in months and a 30-day clock. On a project where you are carrying financing or waiting on rental income, that is not a small saving.
Cost
A full custom ADU plan set runs about $10,000. When a design is already pre-approved for your city, that cost is spread across every unit built from it rather than landing entirely on your project.
The plan is standardized. Your site is not. Geotech, utility runs, sitework and demolition still swing the number substantially, and permit and impact fees are separate. Anyone quoting you a single fixed price for a pre-approved ADU is quoting the building and ignoring the lot.
Two constraints worth knowing
| Constraint | What it means for you |
|---|---|
| Approval is tied to the current building code cycle | California updates its building standards on a three-year cycle. A plan approved under the previous cycle needs re-approval — always confirm a plan is current before relying on it |
| Each city is a separate submission | A plan pre-approved in one city is not automatically approved in the next one over. The program is per-jurisdiction |
The question to ask your city
Whatever else you do, ask this directly, and ask it early:
"Do you have a pre-approved ADU plan program under AB 1332, and where are the approved plans posted?" If the answer is no, the city is out of step with state law — and it is worth asking again, higher up.
We ask this on every ADU project, in every jurisdiction, before we price the design phase. It is one of the few places in residential construction where the law moved in the homeowner's favor and the savings are real.
Common questions
What is AB 1332?
Does AB 1332 apply to charter cities?
How long does a pre-approved ADU permit take?
Does a pre-approved plan mean a fixed price for my ADU?
Where do I find my city's pre-approved ADU plans?
Where to go next
Written by the team at Elusive Construction, a licensed California general contractor (B #1112902) building in Santa Clara and San Mateo counties. General information about how residential construction works — not legal advice. For your specific contract, talk to an attorney.
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