A junior accessory dwelling unit (JADU) is a unit of no more than 500 square feet created entirely within the walls of an existing or proposed single-family home, including an attached garage. It needs its own entrance and an efficiency kitchen (a sink, a cooking appliance, and food prep counter space) but can share a bathroom with the main house.
JADU versus ADU
| JADU | ADU | |
|---|---|---|
| Max size | 500 sq ft | 800 sq ft state exempt; 1,000 to 1,200 local |
| Location | Inside the existing single-family home or attached garage | Detached, attached, or converted |
| Kitchen | Efficiency kitchen | Full kitchen |
| Bathroom | Own or shared | Own |
| Owner-occupancy | Only if bathroom is shared (from 2026) | None |
| Separate utility connection | Not required | Often required for detached |
| Impact fees | Exempt | Exempt under 750 sq ft |
The two-ADU rule
JADUs matter because they stack. A single-family lot can have one JADU and one detached ADU at the same time, which turns a house into three rentable units without a lot split. Read the two-ADU rule guide for the full combination.
AB 1154 and owner-occupancy in 2026
Until the end of 2025, every JADU required the owner to live in either the JADU or the main house, recorded as a deed restriction. AB 1154, effective January 1, 2026, limits that requirement to JADUs that share sanitation facilities with the primary dwelling. Give the JADU its own bathroom and the owner-occupancy requirement disappears, which makes JADUs usable by investors and in rental portfolios.
Cost and rent
Because a JADU reuses existing walls, roof, and foundation, it is the cheapest unit you can add: typically $60,000 to $140,000 for a bedroom-and-bath conversion with an efficiency kitchen. A 450 square foot studio JADU in Los Angeles County rents for roughly $1,600 to $2,100 in 2026.
How Parcy treats JADUs
When you run a single-family address, Parcy offers a JADU as a converted-space unit alongside the detached ADU, prices the conversion, and shows the combined rent and return on cost. Get the app.
Frequently asked questions
What is the maximum size of a JADU?
500 square feet, within the existing or proposed single-family home or attached garage.
Can a JADU share a bathroom with the main house?
Yes. From 2026 under AB 1154, sharing a bathroom is the only case that still triggers an owner-occupancy requirement.
Can I have a JADU and an ADU on the same lot?
Yes. A single-family lot may have one JADU and one detached ADU.
Informational only. Not legal, architectural, or investment advice. Confirm current rules with your local planning department.