It depends on when the ADU was built. For an ADU or junior ADU built before January 1, 2020, California law bars a city or county from denying a permit to legalize it just because it violates building standards or ADU rules, unless the agency finds that correcting a violation is necessary to meet the state’s substandard-building standards; the rule does not cover a building already deemed substandard. An ADU built since then has no such protection. And in the City of Los Angeles, work started without a permit that violates the City’s building regulations carries an investigation fee of double the permit fee.
Two state laws cover older units: one that sets up a route to a permit, and one that lets an owner ask for enforcement to be delayed. Here is what each says, in its own terms. This is general information, not legal advice.
Built before 2020: the route to a permit
Government Code section 66311.7 sets the rules for a previously unpermitted ADU or junior ADU constructed before January 1, 2020. AB 2533 enacted the current version as section 66332, effective January 1, 2025, and SB 543 renumbered it to 66311.7 on January 1, 2026, without changing the rule.
| Question | What the law says |
|---|---|
| Can the city or county deny the permit? | Not because the unit violates building standards, or because it does not comply with state ADU law or a local ADU ordinance |
| When can it deny the permit? | When the agency makes a finding that correcting the violation is necessary to meet the standards in Health and Safety Code section 17920.3, the state’s list of substandard building conditions |
| Are there buildings the rule does not cover? | Yes. It does not apply to a building deemed substandard under section 17920.3 |
| What about impact fees? | The homeowner is not required to pay impact fees or connection or capacity charges, except where utility infrastructure is required to meet section 17920.3 and the fee is one the state ADU law allows for a new utility connection (Government Code 66311.5(e)) |
| What can the inspector do? | Inspect the unit for health and safety standards and recommend what is needed for a permit. If the unit falls short, the agency cannot penalize the owner for having it and must approve the permits needed to correct it |
| Can the owner check first? | Yes. The law requires local agencies to tell homeowners they may get a confidential third-party code inspection from a licensed contractor before applying |
The five-year enforcement delay
A separate law, Health and Safety Code section 17980.12, deals with an ADU that has already drawn a notice to correct a building standards violation:
| Point | What the law says |
|---|---|
| Who qualifies | An ADU built before January 1, 2020, or built later in a jurisdiction whose ADU ordinance was noncompliant when the unit was built and is compliant when the request is made |
| What the notice must say | That the owner has the right to request a delay in enforcement |
| What the owner can ask for | A five-year delay, on the basis that correcting the violation is not necessary to protect health and safety |
| When it must be granted | When the enforcement agency determines the correction is not necessary to protect health and safety, after consulting the agency that enforces State Fire Marshal regulations |
| Deadline | No new delays can be approved on or after January 1, 2030; a delay approved before then runs its full term |
Built in 2020 or later, or building one now
Neither law covers an ADU built without a permit from 2020 on, outside the narrow case above. Unpermitted work also has to be disclosed when you sell, if the seller knows about it; what a homeowner can do without a permit covers California’s disclosure rule. For an ADU still in planning, the permit side is set out in what an ADU is under California law.
The City of Los Angeles investigation fee
Separately, the City of Los Angeles has a general rule for work started without a permit. When that work violates the City’s building regulations (Chapter IX of the Municipal Code) and no order has required it to proceed, LADBS conducts a special investigation before it issues any permit, and charges an investigation fee of double the permit fee, in addition to the permit fees themselves.
How we handle it
We design, permit and build ADUs, including garage conversions, with the permit in place before construction starts. In the City, that runs through LADBS, as described for ADU construction in Los Angeles.
