What is an ADU?
An accessory dwelling unit is a second home on the same lot as a house or apartment building: its own kitchen, bathroom and front door. Also called a granny flat, casita, backyard home or in-law unit.
The kinds
The garage becomes a home. No new setbacks, no replacement parking, and usually the least costly full-size unit.
Learn more
Up to 500 sq ft carved out of the house you have. The smallest budget and the simplest permit.
Learn more
A new wing that shares a wall with the house and has its own front door. Good for narrow lots.
Learn more
Its own building in the back yard. The most privacy of any type.
Learn more
Keep the parking and the yard, add a home upstairs.
Learn moreHow many can you build?
California, 2026
| Property | What's allowed |
|---|---|
| Single-family lot | An ADU plus a JADU; often a conversion, a detached ADU and a JADU together |
| Duplex to fourplex | One detached ADU per unit, plus at least 1 conversion |
| 5+ units | Up to 8 detached ADUs, plus conversions up to 25% of units |
| Single-family, split | SB 9: two lots, up to 2 homes each |
What it's for
A second rent check from land you already own.
Parents close by, or grown kids with their own door.
A second home on the lot adds to what the property is worth.
ADU basics
Is a guest house an ADU?
Only if it has a kitchen and is permitted as an ADU. A guest house without a kitchen usually can't be rented long-term.
Can I sell an ADU separately?
Generally no. AB 1033 allows ADU condos only where a city has opted in; an SB 9 split is the usual path to selling.
How long does it take?
From about 4 to 20 months, first call to move-in. A junior ADU is the quickest, a second story the longest.
When the rules change, you'll know
A short email when ADU law changes in Southern California, plus new projects and plans. A couple of times a month at most. Unsubscribe anytime.
What could your lot hold?
Send the address. Free.