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Junior ADUs (JADUs)

Last updated November 3, 2026

A junior ADU, or JADU, is a unit of no more than 500 square feet of interior living space built entirely within a single-family home. Under Government Code section 66313 it needs an efficiency kitchen and its own exterior entrance, and it may share a bathroom with the main home.

What Defines A JADU

Under Government Code section 66313, a JADU is no more than 500 square feet of interior living space and sits entirely within a single-family residence. It may have its own bathroom or share one with the main home. It must include an efficiency kitchen, which the handbook describes as a cooking facility with appliances, a food preparation counter, and storage cabinets, and it must have its own exterior entrance. If it has no separate bathroom, it must also have an interior door into the main living area. For JADU purposes, an attached garage counts as part of the house (HCD ADU Handbook (March 2026)).

Rules That Matter

• One per lot. A city must allow one JADU per lot with a single-family home, and it can be combined with a converted ADU and a new detached ADU.
• Owner occupancy. If the JADU shares a bathroom with the main home, the owner must live in either the JADU or the remaining part of the house. If it has its own bathroom, owner occupancy is not required (Government Code section 66333).
• Rentals. A JADU cannot be used as a short-term rental. If rented, the term must be longer than 30 days.
• Parking. A city cannot require parking for a JADU, even if a garage is converted.
• Fire sprinklers. A JADU cannot trigger a sprinkler requirement for the house, and none is required for the JADU if the house has none.
• Fees. A JADU of 500 square feet or less is exempt from local impact fees.
• Utilities. A JADU created from existing space cannot be required to have a separate utility connection.

These points come from the HCD ADU Handbook (March 2026), which also gives the statute citations.

What A JADU Costs

We have not found a reliable published cost range for JADUs, so we are not quoting one. Cost depends on whether you add a bathroom, how much plumbing and electrical work is needed, and how the entrance is built. For context, the Terner Center's Terner Center statewide ADU owner survey reports a median of $150,000 for all ADU types, which includes far larger projects. Ask for written estimates and compare. See ADU Cost In California.

JADU Or Full ADU?

• JADU: inside the house, up to 500 square feet, shared walls and often a shared bathroom, owner occupancy in some cases.
• ADU: larger, can be attached or detached, no owner occupancy requirement, usually higher cost.

Lenders And Resale

A JADU with its own entrance and kitchen area changes how the home is used and insured. Talk to your lender, your insurance agent, and the county assessor before you build. They can tell you how a second unit affects your loan, your policy, and your property tax bill.

Related guides: California ADU Rules, Rental Rules And Income, ADU Financing.