JADU vs ADU: What's the Difference?
Short answer: a junior ADU (JADU) is a unit of up to 500 square feet carved out of the interior of a single-family home, including an attached garage. An ADU can be attached, detached, or a conversion, can be considerably larger, and can be rented without the owner living on site.
Side by side under state law
- Location: a JADU must be contained entirely within a single-family residence (an attached garage counts; a detached structure does not). An ADU can be attached, inside the home, or a detached backyard building.
- Size: a JADU is capped at 500 square feet of interior livable space. ADU size limits are set locally within state minimums; check your city.
- Bathroom and owner occupancy: a JADU may share a bathroom with the main house. If it does, owner occupancy of the JADU or main home is required; with its own bathroom, it is not. Cities cannot impose owner occupancy on ADUs.
- Parking: cities may not require parking for a JADU, even one converted from an attached garage. When a garage is converted or demolished for an ADU, replacement parking cannot be required.
- Rentals: a rented JADU must be rented for terms longer than 30 days.
- Review time: for both, the city must approve or deny a complete application within 60 days when there is an existing home on the lot.
- How many: a single-family lot can generally have one ADU and one JADU.
Sources: HCD Accessory Dwelling Unit Handbook (https://www.hcd.ca.gov/sites/default/files/docs/policy-and-research/adu-handbook-update.pdf); Government Code sections 66313, 66314, 66317, 66333, and 66334 (https://leginfo.legislature.ca.gov/faces/codes_displayText.xhtml?chapter=13&division=1.&lawCode=GOV&part=&title=7.).
Which one fits your goals?
A JADU suits a homeowner with an underused bedroom wing or attached garage who wants a modest, lower-scope unit for a relative or caregiver. Because it lives inside the house, privacy and sound separation are limited.
A detached ADU suits owners who want full independence: separate entry, separate utilities where possible, and space for a one- or two-bedroom layout. It is what Type Five designs and builds: custom, wood-framed backyard homes constructed on site.
Many lots can hold both, so the choice is not always either-or.
Not sure which unit fits your lot?
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JADU and ADU FAQs
Quick answers to common questions.
Can I have both an ADU and a JADU?
State law guarantees at least one ADU on a single-family lot, plus one JADU inside the existing house.
Does a JADU need its own kitchen?
A JADU must include an efficiency kitchen. It may share a bathroom with the main house, which triggers owner occupancy.
How long does a detached ADU take?
With Type Five, design takes about one month, permitting about two to four months after we submit plans, and construction about six months on site. Most projects take about 10 to 12 months from first design meeting to move-in.
Will an ADU raise my property taxes?
Your main house assessment stays the same under Prop 13; the assessor adds the value of the new construction separately.