How Tall Can an ADU Be?

Height limits decide whether your ADU can have a second story, a loft, or a tall ceiling — and California sets protective floors that cities must allow.

The baseline: 16 feet

Cities must allow a detached ADU of at least 16 feet in height. That's enough for a comfortable single-story unit with standard ceilings and a pitched roof. No city can force you below this for a qualifying ADU.

18 feet near transit or multifamily

If your property is within half a mile of major public transit, or the ADU sits on a lot with an existing multistory multifamily building, the minimum the city must allow rises to 18 feet — and you can generally add 2 more feet to match the roof pitch of the main house. Those extra feet make lofts and more generous rooflines possible.

Attached ADUs can go higher

For an ADU attached to the main house, cities must allow up to 25 feet or the height limit of the underlying zone, whichever is lower. That's genuine two-story territory. This is why some homeowners who want a second story choose an attached design.

Can a detached ADU be two stories?

Yes — but usually only if your local rules allow more than the state minimums. Many cities do permit taller detached ADUs (some allow 25+ feet), especially outside sensitive zones. The state numbers are floors, not ceilings: your city can always be more generous.

One more consideration before you dream vertical: overhead power lines. A second story can put your roof inside required clearance distances from utility lines — a real constraint we cover in the next lesson.