People build accessory dwelling units for good reasons: a parent nearby with their own front door, an adult child with somewhere to land, rental income, or simply more usable value on a lot that will not get any bigger. Before any of that, though, there is a definitional question worth settling first, because it decides which set of rules your project is reviewed under.
RDD Solutions is a residential design and drafting firm in Carmel. We draw permit-ready plans for homeowners and general contractors across Monterey County. We do not build and we are not an architecture firm. This page answers one question and answers it plainly: what counts as an ADU, what counts as a JADU, and what does not count as either.
The Definition
An accessory dwelling unit is an attached or detached residential unit, on a lot with a primary residence, that provides complete independent living facilities for one or more people (Gov. Code §66313(a)). Complete independent living facilities means permanent provisions for all five of the following:
- Living space
- Sleeping space
- Eating space
- Cooking facilities
- Sanitation, meaning a bathroom
All five, permanently. That is the whole test. Square footage, roof pitch, whether it is attached or detached, whether it sits over the garage or at the back of the lot: none of that changes whether the space is an ADU. The four facilities do.
What a JADU Is, and How It Is Different
A junior accessory dwelling unit is a smaller, more constrained thing (§66313(d)). A JADU:
- is no more than 500 square feet,
- is contained entirely within a single-family residence, and
- may share sanitation with the primary residence rather than having its own.
That last point is the practical difference. A converted bedroom with a small kitchen and its own entrance, still using the main house’s bathroom, can be a JADU. It cannot be an ADU, because it does not have complete independent living facilities of its own.
The classification then follows you. No owner-occupancy requirement may be imposed on an ADU (§66315), and that protection is permanent. A JADU is not treated the same way: where it shares sanitation with the primary residence, owner-occupancy may be required, and JADU rentals must exceed 30 days (§66333). If the plan is to rent, decide which one you are building before anything is drawn.
What Does Not Qualify as an ADU
This is where most of the confusion sits, and where people are most often surprised.
- A guest suite without independent living facilities. A bedroom and a bathroom over the garage, with no cooking facilities, is not an ADU. It is a room. That is not a lesser thing, but it is reviewed as an addition, not under ADU law.
- A bedroom addition. Adding a bedroom and a bath to the back of the house is an addition, full stop, however self-contained it feels once the door is closed.
- A converted room that shares the primary entrance. Independence is not only about plumbing. A space entered through the main house’s living room is not functioning as a separate dwelling, and it will not be treated as one.
- A studio, office, workshop or pool house. Detached, conditioned and beautifully finished, and still not a dwelling unit if it has no sleeping and cooking provisions.
- An RV, trailer or park model. A vehicle is not a dwelling unit, whatever it is parked on.
The reverse trap is more expensive. If you build what you are calling a guest suite and it happens to include a kitchen, a bathroom, sleeping space and its own entrance, you have built an ADU. Calling it something else on the plans does not change what it is, and a unit built as an unpermitted second dwelling is a problem that surfaces at sale, at refinance, or the first time anyone pulls a permit on the property.
The Citation Problem: ADU Law Was Renumbered
One housekeeping point, because it will affect what you find when you go looking. California ADU law used to sit at Government Code §65852.2. It was renumbered into §§66310–66342 effective March 25, 2024.
The substance largely carried over. The citations did not. A page, a checklist or a printed handout still citing 65852.2 as live law has not been updated since that change, which is a fair prompt to check how current the rest of it is. This is not a small housekeeping detail when the document you are relying on is a local ordinance summary or a contractor’s ADU explainer from a few years ago.
Why the Classification Matters
Once a project qualifies as an ADU, it is reviewed under a different and considerably more favorable set of rules than an ordinary addition: approval is ministerial, there are statutory clocks on the agency, parking requirements are sharply limited, and there is a protected size and setback category for a detached new unit. If a project does not qualify, none of that applies and it is reviewed as an addition under your local ordinance.
That is the whole reason to settle the definition first. How that approval process actually runs, what the plan set has to carry, and how the coastal zone changes the picture on this coastline are covered in ADU plans in California and on our ADU design page rather than here. One point worth carrying with you: state ADU law applies in the coastal zone but does not lessen the Coastal Act, so a coastal development permit can still be required for a parcel in Carmel, Pacific Grove, Pebble Beach or the coastal edges of Monterey. Ministerial approval is not a coastal exemption.
Local jurisdictions can also impose standards the state does not, and in Monterey County the zoning and resource setting of the parcel drives which process you are in. Confirm your own parcel with the planning department rather than assuming from any general article, this one included.
Requirements and timelines described here were researched in September 2026 and are typical rather than guaranteed. Verify current requirements with the building department for your jurisdiction.
If It Is Not an ADU, It Is an Addition
Plenty of good projects are not ADUs and should not be. If you want the space attached, conditioned and part of the main house, without the separate-dwelling classification and the separate utility, occupancy and rental consequences that come with it, then what you want is a home addition. Where a guest suite sits on that line is worth settling in the first conversation, not at plan check.
Frequently Asked Questions
What qualifies as an ADU in California?
An attached or detached residential unit on a lot with a primary residence that provides complete independent living facilities for one or more people, meaning permanent provisions for living, sleeping, eating, cooking and sanitation (Gov. Code §66313(a)). If all four are present and permanent, it is an ADU. If any one of them is missing, it is not.
What is the difference between an ADU and a JADU?
A JADU is no more than 500 square feet, sits entirely within a single-family residence, and may share sanitation with the main house (§66313(d)). An ADU has complete independent living facilities of its own and may be attached or detached. The occupancy rules differ too: no owner-occupancy requirement may be imposed on an ADU (§66315), while a JADU sharing sanitation may carry one, and JADU rentals must exceed 30 days (§66333).
Does a guest suite count as an ADU?
Not on its own. A bedroom and bathroom with no cooking facilities is a guest suite, reviewed as an addition. Add permanent cooking facilities and an independent entrance and you have built a dwelling unit, which is reviewed under ADU law whatever the drawings call it.
Does a converted room with its own entrance count?
It depends on what is inside it. A converted room needs permanent provisions for living, sleeping, eating, cooking and sanitation to be an ADU. A converted room with a kitchenette that still shares the main house’s bathroom and is entered through the primary residence is closer to a JADU, and a room that shares the primary entrance is generally not functioning as a separate dwelling at all.
Why do some sources cite Government Code 65852.2?
Because the law moved. ADU provisions were renumbered out of §65852.2 into §§66310–66342 effective March 25, 2024. The substance largely carried forward, but any document still citing the old section has not been updated since then, and that is worth knowing before you rely on the rest of it.
Find Out What You Are Actually Building
Tell us what the space needs to do and where the property is, and we will tell you whether it lands as an ADU, a JADU or an addition, and what the plan set has to carry either way. Get started with RDD Solutions.