Guide · junior ADUs
A junior accessory dwelling unit is carved out of the walls of an existing or proposed single-family home, capped at 500 square feet. It is governed by its own statutes and differs from a standard ADU in one way that surprises most owners: you still have to live on the property.
JADU: owner-occupancy required. ADU: prohibited.
California bars a city from imposing an owner-occupant requirement on a standard ADU (Gov. Code § 66315). That bar does not extend to JADUs. If a JADU shares sanitation facilities with the house, § 66333(b) allows the requirement, and the owner may live in either the house or the JADU.
| JADU | Detached ADU | |
|---|---|---|
| Max size | 500 sq ft | 800 guaranteed, 1,200 ceiling |
| Must live on site | Yes | No |
| Where it sits | Inside the existing house | Separate building |
| Separate entrance | Required | Inherent |
| Impact fees | None at ≤500 sq ft | None at ≤750 sq ft |
| How many per lot | 1 | 1, plus the JADU |
You can build one of each on a single-family lot.
California found 159 of 164 reviewed city ADU ordinances non-compliant. Under Gov. Code § 66316 a non-compliant ordinance is void in full and state standards apply instead. Check your city →