Junior ADU (JADU) rules in California and San Diego

What is a junior ADU?

California law defines a junior accessory dwelling unit as a unit of no more than 500 square feet of interior livable space contained entirely within a single-family residence. It can have its own bathroom or share the one in the house. Since January 1, 2026, the limit is measured as interior livable space: rooms meant for living, sleeping, eating, cooking or sanitation.

The difference from a regular ADU is where it sits and how much it needs. A standard ADU must have complete independent living facilities, including its own kitchen and bathroom, and can be detached, attached or converted from another building. A JADU is always inside the main house, and the state only asks for an efficiency kitchen. If you're still sorting out the terms, start with what an ADU is and the four types.

Typical JADUs are a spare bedroom suite with an outside door, the back end of a larger house, or part of an attached garage. Space in an attached garage counts as part of the house for this purpose. If you want to convert the whole garage and it's bigger than 500 square feet, a regular garage conversion ADU is usually the better fit.

Junior ADU requirements

Government Code section 66333 sets the conditions every city's JADU rules must include:

Source: Gov. Code § 66333 and the size definition in § 66313. On a single-family lot, a JADU can sit alongside one ADU inside the house or an existing accessory building and one new detached ADU. Cities must approve that combinationministerially. See California ADU laws for how the three units fit together.

The permit itself is ministerial: no hearing, no discretionary review. The city has 15 business days to say whether your application is complete and, where there's an existing house on the lot, 60 days to approve or deny it. A denial has to list what's wrong and how to fix it. The city also can't deny a JADU because of an older zoning nonconformity, code violation or unpermitted structure elsewhere on the property, as long as it isn't a health and safety threat and the JADU work doesn't affect it.

Efficiency kitchen requirements

The statute defines an efficiency kitchen by three things. It must include:

• a cooking facility with appliances,
• a food preparation counter, and
• storage cabinets of reasonable size for the size of the unit.

That's the whole state definition. It doesn't list particular appliances, so ask your city what it accepts for the cooking facility before you finalize the plans. Many owners plan a compact range or cooktop, a small fridge and a sink, which is also what makes the space rentable.

Planning a JADU

Choosing the space

The cheapest JADUs reuse what the house already has: a bedroom suite on an outside wall, close to existing plumbing, where a new door can open to the yard or side path. Every foot of new drain line and every wall you move adds cost. A suite that already has its own bathroom is the easiest case, because it avoids both the interior-door requirement and, under state law, the owner-occupancy rule.

Junior ADU in an attached garage

An attached garage counts as part of the house, so part or all of it can become a JADU, as long as the unit stays at 500 square feet or less. A city can't require you to add parking for a JADU. If the space you want to convert is larger than 500 square feet, make it a regular ADU instead. State law guarantees an ADU inside the existing house, and the City of San Diego sets no maximum size for ADUs converted from existing space. That route needs a full kitchen and its own bathroom, and no city can require you to live on site.

Shared bathroom or its own?

Source for the legal rows: Gov. Code § 66333. In the City of San Diego, check the owner-occupancy row with Development Services first (see below).

Owner occupancy and renting

AB 1154 changed the owner-occupancy rule on January 1, 2026. Before, every JADU required the owner to live on the property. Now the requirement applies only when the JADU shares sanitation facilities with the house.

Source: Gov. Code § 66333 as amended by AB 1154. Regular ADUs are different: no city may require owner occupancyfor an ADU at all.

Can I rent a junior ADU?

Yes. Rentals must be for more than 30 days, so a JADU can't be a nightly or weekly vacation rental. You can't sell it on its own: the recorded deed restriction ties it to the house. For what a small unit rents for, see our guide to ADU rental income in San Diego.

Junior ADUs in San Diego

The City of San Diego allows JADUs of 150 to 500 square feet and requires rentals of at least 31 consecutive days. Its Information Bulletin 400 covers both ADUs and JADUs and is the city's plain-language summary.

The permit process is the same as for an ADU. See the ADU permit process in San Diego for the steps and timeline.

Fees, parking and fire rules

The state keeps a JADU cheap to permit:

• Impact fees: none for a JADU of 500 square feet or less.
• School fees: none for a unit of 500 square feet or less.
• Utilities: a JADU isn't a new or separate unit for water, sewer or power service, including connection fees. A utility can only charge what it charges every single-family home.
• Permit and inspection fees: the city can charge to cover its costs of issuing the permit and inspecting the work.
• Parking: a city can't require any additional parking for a JADU.
• Fire protection: a JADU isn't a new or separate dwelling unit for fire or life-safety rules. A city can only apply fire rules that apply to every single-family home in the zone, with or without a JADU.

That last point matters for cost. An attached ADU is treated as a second dwelling, which can mean a fire-rated separation from the house. A JADU, by statute, isn't. On energy rules, the California Energy Commission says JADUs may be subject to the Energy Code depending on the scope of work.

Junior ADU cost

Lars Remodel, a San Diego design-build firm, publishes a planning range of $120,000 to $200,000+ for a JADU as of October 2026. For comparison, it lists $150,000–$225,000+ for a garage conversion ADU, $200,000–$350,000+ for an attached ADU and $250,000–$450,000+ for a detached ADU.

The same source names the main JADU cost drivers: the efficiency kitchen and required separation, plus privacy, egress, shared systems and the existing layout. Moving plumbing to reach a new kitchen or bathroom is where budgets grow. These ranges are one builder's experience, not quotes. For the full breakdown, see what an ADU costs in San Diego or try the ADU cost calculator.

JADU vs ADU

Sources: Gov. Code §§ 66313, 66314, 66315, 66321, 66322, 66323, 66333, 66334, 66342 and 66311.5; Lars Remodel. A JADU wins on cost and permit simplicity if you have a spare room with an outside wall. An ADU wins on size, privacy and flexibility, since it can be rented with no one living on site. When you're ready for bids, compare verified ADU builders in San Diego, check a contractor's license, and read how to hire an ADU contractor before you sign.

Common questions