What Is a Junior ADU (JADU)?
A Junior Accessory Dwelling Unit (JADU) is a small residential unit created within the existing footprint of a single-family home. JADUs are capped at 500 square feet and must include a cooking facility (can be an efficiency kitchen — sink, counter, small appliance outlet, and a place for a portable cooking device).
JADUs are the fastest, cheapest, and easiest type of ADU to build in California.
JADU Rules in California (2026)
- Maximum size: 500 square feet.
- Location: Must be within the existing or proposed footprint of the primary residence (including attached garages).
- Entrance: Must have a separate exterior entrance from the main dwelling.
- Kitchen: An efficiency kitchen is required (can be minimal — no full stove required).
- Bathroom: Can share a bathroom with the primary residence OR have a separate one.
- Owner occupancy: The homeowner must live in either the main house or the JADU (unlike regular ADUs, JADUs do require owner-occupancy).
- Parking: No additional parking required.
- Deed restriction: A deed restriction is recorded stating the property cannot be sold separately from the primary residence.
JADU vs. Regular ADU
| Feature | JADU | ADU |
|---|---|---|
| Max size | 500 sq ft | 1,200 sq ft |
| Location | Within existing home | Attached or detached |
| Cost | $50K – $100K | $150K – $450K |
| Owner occupancy | Required | Not required (post-2020) |
| Can have both? | Yes — California allows one ADU + one JADU on single-family lots | |
Best Use Cases for a JADU
- Converting a spare bedroom + adding kitchenette: Minimal construction, maximum return.
- Attached garage conversion: Reframe the garage space into a studio apartment within the home's footprint.
- Aging parent suite: Keep family close with an independent-but-connected living space. Read our aging-in-place guide.
- Supplemental income on a budget: $50K–$100K investment generating $1,200–$2,000/month.
JADU Cost Breakdown
- Efficiency kitchen installation: $8,000 – $15,000
- Bathroom (new or upgrade): $10,000 – $25,000
- Separate entrance: $3,000 – $8,000
- Insulation / soundproofing / fire separation: $5,000 – $12,000
- Permits and plans: $1,000 – $4,000
- Finishes: $10,000 – $25,000
Interested in a JADU? Get matched with contractors experienced in JADU conversions.
📘 Want the complete guide?
Download our free 34-page Stress-Free Guide to Building an ADU in California — updated for 2026.
Get the Free Guide →
Download our free 34-page Stress-Free Guide to Building an ADU in California — updated for 2026.
Get the Free Guide →