A junior accessory dwelling unit (JADU) is a small, independent living space of up to 500 square feet created inside an existing single-family home, or inside its attached garage. In the Bay Area, where adding a full backyard ADU is not always practical, a JADU is often the simplest way to create space for a family member, a caregiver or a tenant. Here is how California law defines a JADU and how it differs from a regular ADU.
What counts as a JADU in California
- Size: no more than 500 square feet.
- Location: within the walls of a single-family home, which can include an attached garage.
- Entrance: its own exterior entrance, separate from the main entrance of the house.
- Kitchen: at least an efficiency kitchen, meaning a cooking appliance, a food preparation counter and storage.
- Bathroom: a JADU can have its own bathroom or share one with the main house.
JADU vs. ADU
| JADU | ADU | |
|---|---|---|
| Maximum size | 500 sq ft | At least 800 sq ft guaranteed; many Bay Area cities allow 1,000 to 1,200 sq ft |
| Where it can go | Inside the house or an attached garage | Detached, attached, or a conversion of a garage or other space |
| Kitchen | Efficiency kitchen at minimum | Full kitchen |
| Bathroom | Own or shared with the house | Its own |
| Owner occupancy | Can apply, especially when the bathroom is shared | Cannot be required |
| Parking | None required | Often none required, depending on location and type |
A single-family lot can usually have both: for example, a detached ADU in the backyard plus a JADU inside the house. Some cities, such as Los Altos, allow two JADUs.
Owner occupancy and deed restrictions
JADUs have traditionally required the owner to live on the property and a recorded deed restriction. State law has narrowed this in recent years, and owner occupancy now generally applies when the JADU shares a bathroom with the main house. Local ordinances do not always reflect the latest state law, so we confirm your city’s current requirements before design.
Why homeowners choose a JADU
- It reuses space you already have, such as a bedroom suite or part of an attached garage, instead of building a new structure.
- Cities generally cannot require a separate utility connection or charge impact fees for a JADU.
- Fire sprinklers are generally not required in a JADU if they are not required in the main house.
- It can be rented for terms longer than 30 days, subject to your city’s rules.
Is a JADU right for your home?
A JADU works best when part of the house already has, or can easily get, an exterior door, and when plumbing for a kitchenette and bath is nearby. If you need more than 500 square feet or a fully separate home, a garage conversion or a backyard ADU may fit better.
Axiom Renovation (CA Lic. #1105006) designs, permits and builds JADUs and ADUs across the Bay Area. See the rules for your city in our Bay Area ADU guide, or book a free site assessment.
