ADU comparisons
JADU vs ADU: size, kitchen, bathroom and the rules
By the HyreADU research desk. Last checked .
The short answer
JADU vs ADU is a California distinction. A junior ADU is no more than 500 square feet, sits inside a single-family house, needs its own entrance and an efficiency kitchen, and may share the house’s bathroom.
A full ADU has complete living facilities, can be attached, detached or a conversion, and can be much larger. A lot can have one of each.
| Factor | Junior ADU (JADU) | ADU |
|---|---|---|
| Where it sits | Within the walls of a single-family house | Detached, attached, or inside an existing structure |
| Size | No more than 500 sq ft | Set locally, but a city may not cap it below 850 sq ft (§ 66321(b)(2)) |
| Kitchen | Efficiency kitchen | Full kitchen |
| Bathroom | May share the main house bathroom | Its own |
| Separate entrance | Required | Required |
| Permit decision | 60 days (Gov. Code § 66335) | 60 days (Gov. Code § 66317) |
When a JADU wins
A JADU wins when there is a spare bedroom or a large primary suite that can be closed off with its own door.
Because it stays inside the house, it usually avoids new foundations and long utility runs.
Impact fees do not apply to a JADU of 500 square feet or less under Gov. Code § 66311.5.
A JADU also suits a household that wants a semi-private space for a relative who will share the bathroom. Read the junior ADU definition for the exact rules.
When a full ADU wins
A full ADU wins when you want a home that works on its own: its own bathroom, a full kitchen, and room for a tenant or family member to live independently.
It is also the only option if the space you want to use is outside the house, such as a garage or the rear yard.
Because a full ADU is larger and complete, it is usually the better rental unit. See ADU rental income for how to estimate rent without guesswork.
The owner-occupancy difference
The JADU article has its own rules on who must live on the lot, separate from the full ADU rules in Gov. Code § 66315. California law generally bars owner-occupancy rules for full ADUs. For JADUs, read your city’s ordinance and Gov. Code § 66333 before you plan to rent both units.
A mistake to avoid
The mistake to avoid is planning a JADU that cannot pass the size test. The 500 square foot limit counts the JADU’s own floor area inside the house, so a large primary suite plus a hallway can exceed it. Measure the space you plan to close off and confirm the measurement method with your city.
What to do next: check your lot with the ADU feasibility checker, read the questions to ask an ADU builder, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.
Get ADU optionsQuestions
Can I have a JADU and an ADU on the same lot?
Yes, in California a lot with a single-family house can have one JADU plus one ADU, subject to the state rules.
Does a JADU need its own bathroom?
No. A JADU may share the main house bathroom. It must have its own entrance and an efficiency kitchen.
Can a garage become a JADU?
A JADU must sit within the single-family house. An attached garage can qualify in some cases; a detached garage is converted to a full ADU instead. Confirm with your city.
Is a JADU outside California?
The term is a California legal category. Other states use their own terms and rules.
Sources
- Gov. Code § 66313 (ADU and junior ADU definitions). Checked October 7, 2026.
- Gov. Code § 66333 (junior ADU ordinances). Checked October 7, 2026.
- Gov. Code § 66335 (junior ADU permit decision). Checked September 5, 2026.
- Gov. Code § 66317 (ministerial review, completeness and the 60-day decision). Checked September 5, 2026.
- Gov. Code § 66311.5 (ADU impact fees, connection fees and capacity charges). Checked September 5, 2026.
- Gov. Code § 66315 (no extra standards; rentals of 30 days or longer). Checked September 5, 2026.
HyreADU is a publisher. It does not design, permit or build ADUs, has no partner builders, and gives no legal, tax, lending or engineering advice.
Rules vary by state and city; California rules are labeled as such. Spotted an error? Tell us through our corrections page. Licensed professionals can also contribute as named sources.