Ask a contractor how tall your ADU can be and you'll usually hear the same number: 16 feet. It's the number that circulates at lumber yards and in Facebook groups, and it comes from state law. But it's not the whole story — because 16 feet is what every city must allow, not what your city does allow. We went and counted.
We compared the ADU rules of 483 California cities, and the short version is this: the state guarantees a detached ADU of at least 16 feet in height with side and rear setbacks of no more than 4 feet (§ 66321, § 66314) — and 87 cities in our count allow taller than that floor, 59 cities require zero parking spaces, and a handful allow units bigger than the state's own maximum framework.
The floor is not the ceiling
California's ADU statutes work in one direction: they limit what a city may require, not what a homeowner may build. A city ordinance that tried to cap detached ADUs below 16 feet, or demand a 10-foot side setback, is preempted — the state floor wins. The 2025 California ADU Handbook puts it plainly: a city may not impose a height limit less than 16 feet for a detached ADU on a lot with a home.
a setback of no more than four feet from the side and rear lot lines shall be required
Nothing stops a city from being more generous. The question nobody had answered with data is: how many actually are?
What 483 city ordinances actually say
| Standard | State floor | What cities do |
|---|---|---|
| Detached ADU height | 16 ft minimum allowance (§ 66321) | Of 204 cities recording a height: 116 sit at 16 ft; 87 allow more |
| Side/rear setbacks | City may require at most 4 ft (§ 66314) | 4 ft is the near-universal local standard |
| Parking | At most 1 space per unit or bedroom (Handbook) | Of 288 cities recording parking: 229 require 1 space; 59 require zero |
| Detached ADU size | Framework up to 1,200 sq ft (Handbook) | 168 cities adopt the 1,200 cap; 5 allow more |
Height: 43% of cities that set a number go above the floor
Of the 204 cities whose profile records a numeric one-story height standard, 116 sit exactly at the 16-foot state floor — and 87, or 43%, allow more. The distribution: 18 ft in 36 cities; 20 ft in 12; 24 ft in 4; 25 ft in 23; 28 ft in 1; 30 ft in 2; 35 ft in 4; and 17 ft in 5.
The most generous group is worth naming. Four cities record a 35-foot allowance: La Habra Heights, Corcoran, La Habra, and Colton. Fresno and Villa Park allow 30 feet, Mountain View 28, and a group of 23 cities — including Beverly Hills and San Luis Obispo — allow 25 feet. In most of these, the taller allowance rides on the underlying zoning district's normal standards, so the practical ceiling on your lot depends on your district.
Parking: 59 cities ask for nothing at all
State law already caps what a city may require at one space per unit or bedroom, whichever is less, and statutory exemptions — transit proximity among them — can zero it out (Handbook: parking). But 59 of the 288 cities recording a parking standard — 20% — have gone further and set the requirement to zero outright, for every ADU, no exemption analysis needed. The other 229 require the single space the state permits.
Size: five cities beat the state's own number
The state framework for a detached ADU runs up to 1,200 square feet, and that number has become the default local cap — 168 cities adopt it exactly. Five go beyond it: Hidden Hills, Menifee, and Woodside allow 1,500 square feet, and Beverly Hills and Fresno allow 1,400.
The rules are moving fast
Of the 399 ordinances in our dataset that carry an adoption or amendment date, 279 — 70% — were adopted or amended in 2023 or later. The state legislature has amended ADU law nearly every session, and cities have been revising to keep up. Whatever you learned about your city's ADU rules more than a year or two ago deserves a re-check.
How we counted
GoCodebook maintains structured ADU rule profiles for 483 California cities, compiled from each city's adopted ordinance and municipal code; 446 of the 483 — 92% — carry a verified ordinance citation. For each standard, we counted the cities whose profile records a local number for it. Where a profile records no local deviation on a standard, state defaults govern that city and it is excluded from that standard's denominator — which is why each statistic states its own base (204 cities for height, 288 for parking). Six height values recorded as zero were treated as data artifacts and excluded. Forty-two cities — 9% of the 483 — record no local deviation on any standard at all. Counts were computed on 2026-08-25; ordinances change, so treat any single city's number as a pointer to its current ordinance, not a substitute for it.
Every city named above links to its rules page, which cites the ordinance section each number comes from.