The laws that open up your lot
California has rewritten its ADU rules almost every year since 2017. These are the ones that matter now, each on its own page.
Pick what fits you
Since January 2025, California lets an existing apartment property add detached ADUs, one for every existing unit up to eight, plus conversions of garages and storage.
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SB 9 lets a single-family lot be split in two, with up to two homes on each.
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Cities must now keep a set of pre-approved ADU plans.
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A garage apartment or back unit built without permits can usually be legalized as an ADU.
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After the January 2025 fires, Los Angeles City and County set up faster rebuild permits.
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Most ADUs are paid for with home equity.
Learn moreWhat every city must allow
Your city can be more generous, never less.
California, 2026
| Rule | The floor |
|---|---|
| Detached ADU size | Cities must allow at least 800 sq ft, and their size cap can't be under 850 sq ft (1 bed) or 1,000 (2+ beds) |
| Setbacks | No more than 4 ft side and rear |
| Height (detached) | 16 ft; 18 ft near transit |
| Parking | None within half a mile of transit; none for conversions |
| Impact fees | None under 750 sq ft |
| Owner occupancy | Not required for ADUs |
| Review time | 60 days on a complete application |
Rules by city
Local rules on top of the state floor.
Which program fits your property?
Send the address. We check every program against it.