ADU law is written jurisdiction by jurisdiction, on top of a state floor. We cite the section and the date, because a rule without either is not usable.
ADU regulations cover size, height, setbacks, lot coverage, parking, owner-occupancy, rental terms and fire requirements. In California, Gov. Code §§ 66310–66342 set statewide minimums that local ordinances cannot go below; everything else is local. A rule quoted without its jurisdiction and effective date cannot be relied on.
What moves it
The California floor, by section
The provisions below are the ones that most often decide a project. Current numbering after SB 477 (2024) and SB 543 (2026).
1Size
§ 66321(b)(2): no maximum below 850 sq ft, or 1,000 sq ft for more than one bedroom. § 66321(b)(3): nothing may prevent an 800 sq ft unit with four-foot side and rear setbacks.
2Height
§ 66321(b)(4): 16 ft detached; 18 ft near transit plus 2 ft for roof pitch; 25 ft or the primary limit, whichever is lower, for attached.
3Setbacks
§ 66314(d)(7): no setback required for a conversion of existing living area or an accessory structure rebuilt in the same location and dimensions.
4Parking
§ 66314(d)(10)(A): no more than one space per unit or per bedroom, whichever is less, and tandem on a driveway is allowed. § 66314(d)(11): no replacement of parking lost to a garage conversion.
5Owner-occupancy
§ 66315: local agencies may not impose an owner-occupant requirement on an ADU on a single-family lot. JADUs are treated separately.
6Rental term
§ 66323: a rental created under the by-right section must be for a term longer than 30 days.
7Fire sprinklers
§ 66314(d)(12): not required if not required for the primary residence, and an ADU does not trigger retrofit of the main house.
01
Owner-occupancy: the rule that changed
Section 66315 provides that § 66314 establishes the maximum standards a local agency may use, and that no additional standards may be imposed, "including an owner-occupant requirement" — except that the agency may require rentals be for terms of 30 days or longer.
This is worth stating plainly because a great deal of older material online still describes owner-occupancy as a requirement. It was, historically, in many jurisdictions.
Two limits on how far to take this. We looked for a sunset or expiry on that prohibition and did not find one. And it does not cover junior ADUs, which sit in a separate article with their own owner-occupancy treatment.
02
Why the recodification matters for anything you read
State ADU Law used to sit at Government Code § 65852.2. SB 477 (Stats. 2024, ch. 7), an urgency measure effective 25 March 2024, moved it into §§ 66310–66342. SB 543 (Stats. 2025, ch. 520) then renumbered the fee section from § 66324 to § 66311.5, effective 1 January 2026.
A guide that still cites § 65852.2 is citing a repealed numbering. That is a fast and reliable test of how current any ADU source is, including ours — every section on this site is cited in the current numbering, and the change log records what moved.
03
The state floor is not your local answer
Everything above is a floor. Your jurisdiction may be more permissive, and on the points the state has not occupied it may be considerably more restrictive.
That is why the locations layer exists and why a city appears in it only once its own code supplies the record. Where a city has not been recorded, we say so rather than showing you the state default with a city name on it — a floor is not an answer.
Do I have to live on the property to build an ADU?
In California, no — Gov. Code § 66315 prohibits a local agency from imposing an owner-occupant requirement for an ADU on a lot with a single-family dwelling. Junior ADUs are covered by a separate article with its own treatment. Outside California, owner-occupancy requirements remain common.
How tall can an ADU be?
In California the statutory floor is 16 feet for a detached ADU, 18 feet near transit plus two feet for a roof pitch, and 25 feet or the primary dwelling’s limit (whichever is lower) for an attached ADU — Gov. Code § 66321(b)(4). Your jurisdiction may allow more.
Can the city make me add parking?
In California it may require no more than one space per ADU or per bedroom, whichever is fewer, and tandem parking on a driveway satisfies it (§ 66314(d)(10)(A)). Several exemptions remove the requirement entirely, and parking lost to a garage conversion need not be replaced (§ 66314(d)(11)).
Can I rent my ADU short-term?
Under Gov. Code § 66323 a rental created under the by-right provisions must be for a term longer than 30 days, and § 66315 lets an agency impose the same 30-day floor generally. Short-term letting is separately regulated by many cities. See our short-term rental research.
Three short steps: the ADU you want, your home, and how to reach you. Nothing goes to a contractor unless you agree.
A straight answer: our ADU professional matching is still being built, so this is not a quote service, and we cannot tell you whether your lot qualifies. We can help you work out which questions to ask and what a thorough proposal should contain. Your planning department decides what is permitted at your address.
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