Updated October 6, 2026
A JADU is a unit of no more than 500 square feet of interior livable space, built entirely inside the walls of a single-family house. California law defines it in Government Code section 66333, and it may include its own bathroom or share one with the main house.
If you own an apartment building, the useful fact is the one most JADU pages bury: a JADU cannot be built on a multifamily lot. California's Department of Housing and Community Development (HCD) says so in its ADU Handbook (March 2026): JADUs may only be built on a site with a proposed or existing single-family dwelling.
Four features separate it from a regular ADU:
One detail surprises people: an attached garage counts as part of the single-family residence for JADU purposes. A garage conversion into a JADU is legal. A garage that is detached from the house is not eligible.
The statute ties a JADU to a single-family dwelling, and the line is sharp. HCD's handbook treats two attached units on one lot, a duplex, as multifamily, so there is no JADU. A half-plex, two homes on separate lots that share a wall, is different. It can have one JADU in areas zoned single-family.
So the real question for an owner of a four-unit or forty-unit building is not "can I add a JADU?" It is "which ADU can I add?" State law answers that one in your favor:
Those are the 66323 categories in HCD's handbook. Your city or county may be more generous than the state minimum, never stingier. Confirm what your local permitting agency allows before you count a unit into a pro forma.
Some multifamily owners also hold a few single-family houses, and that is where JADU rules bite.
Owner-occupancy. If the JADU shares a bathroom with the main house, the owner must live in either the main house or the JADU. If it has its own bathroom, no owner-occupancy requirement applies. A regular ADU carries no owner-occupancy requirement at all, so the bathroom decides which rulebook you are under.
Rental term. A JADU cannot be a short-term rental. If you rent it, the term must be longer than 30 days.
HCD adds that a JADU cannot trigger a fire sprinkler requirement if the main house has none, and a local agency cannot require parking for one, even when it replaces an attached garage.
A JADU is part of the house, not a separate asset, and it carries conditions that travel with the property: the shared-bathroom owner-occupancy rule and the 30-day rental floor. A buyer of a house with a JADU inherits both. Confirm with your city that the unit was permitted. For an unpermitted one, ask your attorney what your options are before you list.
For an apartment building, what a buyer cares about is your ADU capacity, not a JADU. See what an open ADU permit does to a sale and whether adding an ADU raises a building's value. If the lot is single-family, SB 9 is the other tool, covered in SB 9 lot splits explained.
A JADU is the one kind of accessory unit state law will not let you build on an apartment lot, and the one apartment owners ask about anyway. The unit you can build is the one HCD calls a 66323 unit, and it is bigger.
What is a JADU?
A junior accessory dwelling unit: a unit of no more than 500 square feet of interior livable space, contained entirely within a single-family residence. It needs an efficiency kitchen, and it may share a bathroom with the main house or have its own.
What does JADU stand for?
Junior Accessory Dwelling Unit. It is "junior" because state law caps it at 500 square feet and requires it to sit inside the existing house, where a regular ADU can be larger, attached, or detached. The term is defined in California Government Code section 66333.
What is a JADU in real estate terms?
A conversion unit carved out of an existing house, usually a bedroom, a garage or a section of one, that works as a small separate apartment. For a seller, it adds rentable space to a single-family property. For multifamily buildings it is not available.
What is the difference between a JADU and an ADU?
A JADU is capped at 500 square feet and must be inside the house. An ADU can be detached, attached or converted and can be much larger. A JADU may share a bathroom with the house. An ADU needs complete independent living facilities. An ADU carries no owner-occupancy requirement. A JADU does when it shares a bathroom.
Can I build a JADU on an apartment building lot?
No. HCD's ADU Handbook says JADUs may only be built on a site with a single-family dwelling. Multifamily owners can add conversion ADUs and detached ADUs under Government Code section 66323 instead.
Does a JADU have to be owner-occupied?
It depends on the bathroom. If the JADU shares sanitation facilities with the main house, the owner must live in the main house or in the JADU. If the JADU has its own bathroom, owner-occupancy is not required.
Can I rent a JADU as a short-term rental?
No. A JADU cannot be a short-term rental. If you rent it, the term must be longer than 30 days.
Does a JADU need its own parking spot?
No. A local agency cannot require parking as a condition of permitting a JADU, even when an attached garage is being converted.
Can I have a JADU and an ADU on the same lot?
On a single-family lot, yes. State law lets one converted ADU, one JADU and one new detached ADU combine. Only one JADU is allowed per lot.
What does "JADU là gì" mean?
It is Vietnamese for "what is a JADU?" The answer is the same: a unit of up to 500 square feet built inside a single-family house, defined by California Government Code section 66333.
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