What is an ADU?
An Accessory Dwelling Unit is a fully independent small home on your property. It has its own kitchen, bathroom, and entrance, and can be detached, attached, or a garage conversion. Maximum size under state law is 1,200 sq ft (or larger by local ordinance).
What is a JADU?
A Junior Accessory Dwelling Unit is a smaller unit that lives inside the existing footprint of your main house. By state law:
- Maximum 500 sq ft
- Must be created from existing space inside the main house
- May have an efficiency kitchen (not necessarily a full kitchen)
- May share a bathroom with the main house
- Owner must live on the property (either in the main house or the JADU)
Side-by-side comparison
| Feature | ADU | JADU |
|---|---|---|
| Maximum size | 1,200 sq ft | 500 sq ft |
| Location | Detached, attached, or garage conversion | Inside the main house only |
| Kitchen | Full kitchen required | Efficiency kitchen allowed |
| Bathroom | Own bathroom required | Can share with main house |
| Owner occupancy required | Varies | Yes, always |
| Sellable separately | Sometimes (AB 1033) | No |
| Typical timeline | 4-9 months | 2-4 months |
When a JADU makes sense
- You have a spare bedroom or office that can be converted.
- Your budget is tight.
- You want to house a family member, not maximize rental income.
- You want the fastest path to a permitted accessory unit.
Once you have identified eligible space, our junior ADU floor-plan checklist helps you sketch the kitchen, bath, and separate entry before you commission drawings.
When an ADU makes sense
- You want maximum rental income.
- You want a separate, fully private unit.
- You may want to sell the unit separately someday.
- You want the unit to be detached or have its own outdoor space.
You can often build both
Many California cities allow one ADU plus one JADU on the same single-family lot. Combined, that gives you the main house, a JADU inside it, and a detached ADU in the back — three legal dwellings on one parcel.
Related reading
Frequently asked questions
Can I rent out a JADU on Airbnb? Most California cities prohibit short-term JADU rentals. Long-term (30+ day) rentals are allowed.
Do JADUs require their own utility meters? No. JADUs typically share utilities with the main house.
Does a JADU count as an ADU for SB 9 purposes? No. SB 9, ADU law, and JADU law are separate frameworks that sometimes stack.