State law guarantees you can build at least an 800 square foot ADU with 4 foot side and rear setbacks. A detached ADU can be 16 feet tall, or 18 feet near major transit plus 2 feet to match the roof pitch. An attached ADU can reach 25 feet or the zone's height limit, whichever is lower.
California's ADU law, now in Government Code sections 66310 to 66342, sets a floor that every city must allow. Los Angeles applies those rules alongside its own ADU ordinance, so the numbers below are the starting point for almost every lot in the city.
Rules at a glance
| Rule | Limit | Code |
|---|---|---|
| Size the city must allow | At least 850 sq ft of interior livable space, or 1,000 sq ft with more than one bedroom | Gov. Code 66321(b)(2) |
| Guaranteed ADU | 800 sq ft with 4 ft side and rear setbacks | Gov. Code 66321(b)(3) |
| Height, detached | 16 ft; 18 ft within 1/2 mile of major transit, plus 2 ft to match the roof pitch | Gov. Code 66321(b)(4)(A), (B) |
| Height, attached | 25 ft or the zone limit, whichever is lower | Gov. Code 66321(b)(4)(D) |
| Side and rear setbacks | 4 ft; none for an ADU inside existing space | Gov. Code 66314(d)(7), 66321(b)(3) |
| Impact fees | None at 750 sq ft or less | Gov. Code 66311.5(c) |
How many units fit on a single-family lot
On a single-family lot, state law allows one ADU created inside existing space and one JADU, plus one new detached ADU of up to 800 square feet. A JADU is a junior unit of up to 500 square feet built inside the walls of the house, including an attached garage.
When an ADU is created inside existing space, such as a garage, no new setback is required for that space. Converting an existing accessory structure may add up to 150 square feet, limited to what is needed for entry and exit.
Parking
A city can require at most one parking space per ADU, and none at all in many cases, including when the ADU is:
- within a half mile walk of public transit
- in a historic district
- part of the house or an existing accessory building
- within one block of a car share vehicle
When a garage or carport is converted or torn down for an ADU, the city cannot require you to replace that parking.
Fees
An ADU of 750 square feet or less pays no impact fees. Larger units can be charged in proportion to the size of the main house. LADBS's ADU bulletin starts proportional fees at 750 square feet, so if you want to avoid impact fees entirely, keep the unit just under 750. School fees apply only to units of 500 square feet or more.
Occupancy, sprinklers, and solar
Owner occupancy: a city cannot require you to live on the property to build or rent an ADU. A JADU that shares a bathroom with the house is the exception: the owner must live in either the house or the JADU.
Fire sprinklers: an ADU does not need sprinklers if the main house is not required to have them, and adding an ADU cannot trigger sprinklers in the house.
Solar: under the 2025 Energy Code, a newly built detached ADU needs solar panels. An ADU that shares a wall with the house counts as an addition and does not. One joined only by a breezeway counts as new construction and does.
LA's two routes
In the City of Los Angeles you can permit an ADU under state law or under the city's own ordinance, LAMC 12.22 A.33. The state route is capped at 800 square feet with the strongest protections; the city route can reach 1,200 square feet detached with more conditions. We compare them in State ADU vs. LA Ordinance ADU, and cover timing in how long LA ADU permits take.
Look up your address on ZIMAS, the City of Los Angeles's free online parcel map. It shows your lot's zone and height district, and whether it sits in a specific plan, a historic district (HPOZ), or another overlay. Those details decide which of the rules above apply to your property.
Common questions
How big can an ADU be in Los Angeles?
State law guarantees at least 800 square feet with 4 foot side and rear setbacks, and a city's maximum cannot be lower than 850 square feet, or 1,000 square feet with more than one bedroom. Under LA's own ordinance, a detached ADU can reach 1,200 square feet unless other zoning limits cap it lower.
How tall can a detached ADU be?
16 feet in most cases. Within a half mile of a major transit stop or high-quality transit corridor it can be 18 feet, plus 2 feet if the roof pitch matches the main house.
Do I have to live on the property?
Not for an ADU. State law bars owner-occupancy requirements for ADUs. A JADU that shares a bathroom with the house requires the owner to live on site.
HCD ADU Handbook (March 2026) | Gov. Code 66321 | LA City Planning ZA Memo 143 | CEC 2025 ADU guide
Rules change and every lot is different. This guide is general information, not advice for your property; confirm the rules for your lot before you design or build.