What Is an ADU
ADU stands for accessory dwelling unit: a second, self-contained home on a lot that already has a house. It has its own kitchen, its own bathroom, and its own entrance. A converted garage is one of the most common ways to get one in San Diego County, because the foundation, walls, and roof already exist.
California ADU law was renumbered by SB 477 in March 2024. The sections cited here are the current ones, Gov. Code 66310 to 66342. Local overlays still apply to your parcel, so confirm your specifics with your city building department or San Diego County before finalising plans.
What the rules actually say
- A full ADU is self-contained: its own kitchen, bathroom, and entry, whether attached to the house or detached from it
- A junior ADU (JADU) is the smaller version. State law defines it as "no more than 500 square feet of interior livable space" and "contained entirely within a single-family residence" (Gov. Code 66313(d))
- An attached garage counts as part of the residence for JADU purposes, so it can become a JADU. A detached garage cannot, and takes the full-ADU path instead (Gov. Code 66333(d))
- Converting existing space to an ADU is ministerial, meaning staff-level approval without a hearing or discretionary review (Gov. Code 66323)
- The law was renumbered on 2024-03-25 by SB 477. Current sections are Gov. Code 66310 to 66342; anything citing 65852.2 or 65852.22 is out of date
Common questions
What does ADU stand for, and what does ADU mean?
ADU stands for accessory dwelling unit. The ADU meaning in plain terms is a second, independent home on a lot that already has a house: its own kitchen, its own bathroom, its own way in. It is the term California code uses. Granny flat, casita, in-law unit, and backyard cottage are the everyday names for the same thing, and an ADU home is just a house with one of these on the lot.
Is an ADU the same as ADU housing you hear about in the news?
Yes. ADU housing is the policy shorthand for exactly this: adding a small second unit to an existing single-family lot rather than building on new land. California has spent several legislative sessions making it easier, which is why converting a garage is now a ministerial permit rather than a discretionary hearing.
Is a converted garage legally an ADU?
It is once it is permitted as one. State law specifically covers converting existing space: a local agency must ministerially approve an ADU created within the existing space of a single-family dwelling or an accessory structure, which includes an attached or detached garage (Gov. Code 66323).
What is the difference between an ADU and a JADU?
Size and location. A JADU is capped at 500 square feet of interior livable space and has to sit entirely within the single-family residence, which includes an attached garage (Gov. Code 66313(d), 66333(d)). A full ADU has no such containment requirement and can be detached. A detached garage cannot be a JADU for that reason.
Can I rent out an ADU?
Generally yes for long-term rental, and the rules differ between ADUs and JADUs. For a JADU, state law requires owner-occupancy only where the JADU shares sanitation facilities with the main house, and not where it has its own (Gov. Code 66333(b)). Short-term rental rules are local and often stricter. Confirm both with your city before planning around rental income.
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