A common story: an owner submits ADU plans, hears nothing for weeks, then gets a short correction letter, fixes it, and gets another one with new items that could have been flagged the first time. It feels like there's no end date. For an ADU, California law says there is. The permit is reviewed ministerially, with no hearing. The city has 15 business days to say whether the application is complete and 60 days to decide once it is. If it doesn't act in time, the application is deemed approved. A denial has to come with the full list of what to fix, and since January 2026 the owner can appeal in writing. This guide walks through those rules, what happens after the permit is issued, and the separate path for getting a permit for an ADU that was built without one.
This is general information about state law, not legal advice. Cities apply these rules through their own procedures, so confirm the details with your city's ADU staff or an attorney for your situation.
Quick answers
- No hearing: an ADU permit application "shall be considered and approved ministerially without discretionary review or a hearing."
- Completeness: the city has 15 business days to tell you in writing whether the application is complete, and what's missing if it isn't.
- Decision: on a lot with an existing home, 60 days from a completed application to approve or deny; if the city doesn't act, "the application shall be deemed approved."
- Denials and appeals: a denial comes with a written list of what's deficient and how to fix it, and cities must offer a written appeal.
- Unpermitted ADUs: a unit built before January 1, 2020 generally can't be denied a permit just because it doesn't meet current building standards, unless the violation makes it substandard.
What an ADU permit is
An ADU permit is the building permit for an accessory dwelling unit, or for a junior ADU, which California's ADU Handbook from the Department of Housing and Community Development defines as "A unit that is no more than 500 square feet in interior livable space and contained entirely within a single-family residence." If you are also considering a lot split, our guide to SB 9 lot splits and ADUs explains the unit math.
What makes it different from most building permits is how it's reviewed. Government Code section 66317 says "A permit application for an accessory dwelling unit shall be considered and approved ministerially without discretionary review or a hearing," notwithstanding local variance and special use permit rules. Ministerial means staff check the application against objective standards; there's no public hearing and no neighbor vote. The same section adds that "No local ordinance, policy, or regulation, other than an accessory dwelling unit ordinance consistent with this article shall be the basis for the delay or denial" of the permit.
The state also limits what cities can add. Section 66315 says "No additional standards, other than those provided in Section 66314, shall be used or imposed, including an owner-occupant requirement, except that a local agency may require that the property may be used for rentals of terms 30 days or longer." In other words, a city can't make you live on the property to get an ADU permit.
The review clocks
Section 66317 sets two deadlines, and knowing which one applies tells you what to ask for. For how long whole projects take in practice, see our ADU timeline guide.
15 business days to decide if the application is complete
Under the version of section 66317 in effect since January 1, 2026, the permitting agency has to decide whether an application is complete within 15 business days and give written notice, listing any items that are missing. HCD's handbook describes the same rule: "A permitting agency must determine whether an application for an ADU or JADU is complete and provide written notice of the determination not later than 15 business days after the permitting agency received the application."
60 days to approve or deny a complete application
Once the application is complete, the statute says: "The permitting agency shall either approve or deny the application to create or serve an accessory dwelling unit within 60 days from the date the permitting agency receives a completed application if there is an existing single-family or multifamily dwelling on the lot." And if it doesn't: "If the local agency has not approved or denied the completed application within 60 days, the application shall be deemed approved."
Two situations pause or delay the clock:
- You ask for more time. "If the applicant requests a delay, the 60-day time period shall be tolled for the period of the delay." Only ask in writing, and only when you need it.
- You're building a new house at the same time. If the ADU application is submitted with an application for a new single-family or multifamily dwelling on the lot, the agency "may delay approving or denying the permit application for the accessory dwelling unit until the permitting agency approves or denies the permit application to create the new single-family or multifamily dwelling," though the ADU application is still considered without discretionary review or a hearing.
Pre-approved plans can move faster still; our ADU plans guide covers that shorter review.
A practical note: the 60 days run from a completed application, so in our experience the fastest permits come from complete first submittals. Keep dated records of every submittal, completeness notice and correction letter. If a review stalls, those dates are what you point to.
If the city says no
A denial isn't supposed to be a dead end. Section 66317 requires that if the agency denies an ADU application, it "return in writing a full set of comments to the applicant with a list of items that are defective or deficient and a description of how the application can be remedied by the applicant." That's the answer to the drip-feed of corrections: the law expects the whole list at once. Our guide to ADU requirements explains which rules come from state law and which your city adds.
Since January 2026 there is also an appeal. The statute now says that if an application is found incomplete or denied, "the permitting agency shall provide a process for the applicant to appeal that decision in writing to the governing body of the agency or, if there is no governing body, to the director of the agency, as provided by that agency. A city or county shall provide that the right of appeal is to the governing body or, at their option, the planning commission, or both." The agency then "shall provide a final written determination by not later than 60 business days after receipt of the applicant's written appeal."
The statute leaves the filing procedure, including any deadline to file the appeal, to each agency, so ask your city how and by when to file. Again, this is general information; for a disputed denial, talk to your city's ADU staff or an attorney.
After the permit is issued
Start within 180 days. Building permits in California expire if work doesn't start or stops for too long. The California Building Code language, as quoted by the City of Richmond in its permit expiration notice, says: "Every permit issued shall become invalid unless the work on the site authorized by such permit is commenced within 180 days after its issuance, or if the work authorized on the site by such permit is suspended or abandoned for a period of 180 days after the time the work is commenced." Building officials can grant extensions for justifiable cause, and some cities set their own rules, so check yours.
Occupancy follows the main house. Section 66328 says "A local agency shall not issue a certificate of occupancy for an accessory dwelling unit before the local agency issues a certificate of occupancy for the primary dwelling." There is a narrow exception for a detached ADU in a county under a state of emergency proclaimed by the Governor on or after February 1, 2025, where the main house was substantially damaged or destroyed by that event and the ADU has passed its required inspections.
Permitting an ADU that was built without one
Many California lots have a converted garage or back unit that was never permitted. State law now gives owners of older units a real path to legalize them. If the converted garage is a room rather than a unit, our guide to legalizing an unpermitted garage conversion covers that path.
Units built before 2020 can't be denied just for code problems
Section 66332, updated by AB 2533 effective January 1, 2025, says a local agency "shall not deny a permit for an unpermitted accessory dwelling unit or unpermitted junior accessory dwelling unit that was constructed before January 1, 2020," because it violates building standards or because it doesn't comply with the state ADU rules or a local ADU ordinance.
There's an important limit. The agency may still deny the permit "if the local agency makes a finding that correcting the violation is necessary to comply with the standards specified in Section 17920.3 of the Health and Safety Code," which is the state's list of conditions that make a building substandard. And the section "shall not apply to a building that is deemed substandard" under that list.
What else the law gives you
- A look before you apply. Cities have to tell homeowners that "the homeowner may obtain a confidential third-party code inspection from a licensed contractor to determine the unit's existing condition or potential scope of building improvements before submitting an application for a permit."
- Limited fees. A homeowner legalizing a pre-2020 unit "shall not be required to pay impact fees or connection or capacity charges," except when utility infrastructure is required to meet the state's health and safety standards and the fee is authorized under Government Code section 66324(e).
- An inspection with recommendations. The statute says "an inspector from the local agency may inspect the unit for compliance with health and safety standards and provide recommendations to comply with health and safety standards necessary to obtain a permit."
A five-year delay on enforcement
If you've already received a notice to correct violations on an ADU, section 66331 requires the local agency, on the owner's request, to delay enforcement of building standards for units built before January 1, 2020, or built later in a jurisdiction whose ADU ordinance was noncompliant at the time but has since been brought into compliance, subject to Health and Safety Code section 17980.12. That section lets the owner request that "enforcement of the violation be delayed for five years on the basis that correcting the violation is not necessary to protect health and safety," and says the agency "shall grant" the request if it agrees correcting the violation isn't necessary to protect health and safety. This is a delay, not a permit, and the program has a sunset date, so it's best used as time to legalize the unit properly.
Legalizing matters beyond code enforcement: an unpermitted unit can complicate a sale, as our ADU value guide explains, and lenders generally won't count its rent, as covered in our ADU financing guide. If you're legalizing an existing unit, the confidential pre-application inspection is a good first step. Medici Construction Group is one licensed option for that inspection and for the work that follows, holding California A, B and C-10 licenses under CSLB #1114433.
Before you apply: a short checklist
- Get your city's ADU submittal checklist and submit everything on it.
- Note the date you submitted and the date of the completeness notice.
- Count 60 days from the date the application was complete.
- Ask for a delay only in writing, and only if you need one, since it pauses the clock.
- Keep every correction letter; a denial should list everything that needs fixing.
- If the application is denied, ask how and by when to appeal.
For what the ADU itself will cost, including fees, see our ADU construction cost guide. For the full sequence from lot check to final inspection, see how to build an ADU.
Frequently asked questions
Do you need a permit to build an ADU?
Yes. An ADU or junior ADU needs a building permit. In California, the application is reviewed ministerially, without discretionary review or a hearing.
How long does it take to get an ADU permit in California?
By statute, the city has 15 business days to decide whether your application is complete and, on a lot with an existing home, 60 days from a completed application to approve or deny it. Correction rounds before the application is complete add time.
What happens if the city doesn't respond in 60 days?
Government Code section 66317 says that if the local agency hasn't approved or denied the completed application within 60 days, the application shall be deemed approved. The clock pauses if you request a delay.
Can the city deny an ADU permit?
Yes, if the application doesn't meet the ADU ordinance and state standards. The denial must include a written list of the items that are defective or deficient and how to remedy them.
Can I appeal an ADU permit denial?
Yes. Since January 1, 2026, cities must provide a written appeal to the governing body or planning commission, with a final written decision within 60 business days. Each agency sets its own filing procedure.
Can I get a permit for an existing unpermitted ADU?
Often, yes. For units built before January 1, 2020, state law bars denial just for building-standard or ADU-rule violations, unless correcting the violation is necessary under the state's substandard-building standards.
Do I have to live on the property to get an ADU permit?
No. Government Code section 66315 bars cities from imposing an owner-occupant requirement on ADUs, though a city may require rentals of 30 days or longer.
What do I need to submit for an ADU permit?
Your city's ADU checklist lists what it requires. If anything is missing, the city has to tell you in writing within 15 business days.
