Junior ADUs: a small unit inside the home you already have
A junior ADU inside your Simi Valley home: the 500 sq ft limit, efficiency kitchen, separate entrance, deed restriction and when you must live there.
A junior ADU, or JADU, is a unit of up to 500 square feet carved out of your existing house. It needs its own exterior entrance and an efficiency kitchen, and it can share a bathroom with the main house or have its own.
It is the lowest-cost way to create a rentable or family unit because you are mostly remodeling rooms you already own. It suits a spare bedroom suite at the end of a hallway, or an attached garage, which state law counts as part of the house for a JADU.
The JADU rules in one table
The rules come from Government Code sections 66313 and 66333 and HCD's 2026 handbook.
| Requirement | Rule |
|---|---|
| Size | 500 sq ft of interior livable space or less |
| Location | Entirely within the single-family home; an attached garage counts as part of the home |
| Entrance | A separate entrance from the main entrance of the house |
| Kitchen | Efficiency kitchen: cooking appliances, a prep counter and storage cabinets of reasonable size |
| Bathroom | Shared with the house or separate |
| Deed restriction | Recorded; no separate sale from the house; limits on size and attributes |
| Parking | None may be required, even when converted from an attached garage |
| Rentals | Longer than 30 days |
Owner occupancy turns on the bathroom
Under the 2025 changes HCD summarizes in its handbook, a JADU that shares bathroom facilities with the main house requires the owner to live in the house. If the JADU has its own bathroom, that owner-occupancy requirement does not apply. Section 66333 says the same.
So the bathroom decision is also a decision about your future flexibility. Adding a bathroom costs more now, but it lets you rent both the house and the JADU later without living there.
What an efficiency kitchen really requires
HCD is explicit that a city cannot be stricter than the state definition. Required counter or cabinet sizes, specific gas or electric connections and particular appliance types are not authorized, and a 220-volt circuit is not required. A cooktop or range, a sink area, a counter and cabinets sized to the room are enough.
A JADU of 500 square feet or less pays no impact fees and no school fees, and it cannot trigger a fire sprinkler requirement if the house does not already have one. That keeps the soft costs low.
Questions homeowners ask
Can I have a JADU and an ADU on the same lot?
On a single-family lot, yes. Government Code 66323(a) allows one converted ADU and one JADU within the home or an accessory structure, plus one new detached ADU, so a JADU in the house and a cottage in the yard can coexist.
Do I need a separate bathroom for a JADU?
No, but if it shares the bathroom with the house you must live in the house. With its own bathroom, the owner-occupancy requirement does not apply.
Can I sell the JADU separately?
No. The recorded deed restriction prohibits selling a JADU separately from the house.
Can I put a JADU in my attached garage?
Yes. For a JADU, state law treats an attached garage as part of the single-family home, and the City cannot require replacement parking.
Sources
Facts on this page last verified: .
- California Government Code section 66313 (ADU and JADU definitions): https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV§ionNum=66313. (2026-10-05)
- California Government Code section 66333 (JADU requirements): https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV§ionNum=66333. (2026-10-05)
- HCD ADU Handbook, updated for law in effect January 1, 2026: https://www.hcd.ca.gov/sites/default/files/docs/policy-and-research/adu-handbook-update.pdf (2026-10-05)
- Competitor's published summary: Safeway Remodel, 2026 ADU law changes in Ventura County (updated September 16, 2026): https://www.safewayremodel.com/blog/california-2026-adu-law-changes-ventura-county (2026-10-05)
Request a free estimate
Call
Monday to Saturday, 7am to 6pm
CSLB #925152 · B General Building Contractor