Module 5 · Lesson 4
California ADU Height Rules
The three height tiers every California city must allow for ADUs — and how transit proximity and attachment change your ceiling.
You met these numbers in Module 2; here they are as the legal rules, in one tidy list.
The three tiers cities must allow:
- 16 feet — every detached ADU, everywhere. The universal floor.
- 18 feet — detached ADUs within half a mile of major transit, or on lots that already have a multistory multifamily building. Plus 2 bonus feet where needed to match the main house's roof pitch.
- 25 feet (or the zone's limit, whichever is lower) — attached ADUs. The law won't let the cap drop below two usable stories for attached units.
Remember the direction: these are minimums cities must allow, not limits. Plenty of cities allow taller detached ADUs — that's local generosity on top of the state floor, and it's what makes most two-story detached projects possible.
A measuring note: height is measured to the roof, and cities measure slightly differently (peak vs. midpoint of a pitched roof). When your design is within a foot or two of a limit, that measurement method matters — a detail your designer handles, but worth knowing exists.
Key takeaways
- Three state tiers: 16 ft everywhere, 18 ft near transit/multifamily (+2 for roof match), 25 ft attached.
- These are floors cities must allow — many cities permit more.
- Two-story detached ADUs rely on local allowances above the state floor.
- Near a limit, how the city measures roof height matters.