Quick Answer: An ADU (Accessory Dwelling Unit) is a fully independent living unit with its own kitchen and bathroom, up to 1,200 sq ft. A JADU (Junior ADU) is carved out of existing home space, capped at 500 sq ft, and requires an efficiency kitchen — not a full kitchen. ADUs can be detached; JADUs must be within the primary dwelling.
ADU vs JADU in California: Key Differences
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California’s ADU laws allow homeowners to add rental units and housing for family members. Two types of units are available — ADUs and JADUs — and understanding the difference helps you choose the right approach for your San Jose property.
Comparison Table: ADU vs JADU
| Feature | ADU | JADU |
|---|---|---|
| Maximum size | 1,200 sq ft (detached); 50% of primary home | 500 sq ft |
| Location | Detached, attached, or converted (garage/basement) | Within the primary dwelling only |
| Kitchen requirement | Full kitchen with range and sink required | Efficiency kitchen (no range required) with sink and refrigerator |
| Bathroom | Must have its own full bathroom | May share bathroom with primary dwelling (interior door allowed) |
| Entrance | Separate exterior entrance required | Separate exterior entrance required |
| Owner occupancy | Required in some cities (check local rules) | Owner must occupy either the primary home or JADU |
| Rental allowed? | Yes — no short-term rentals (in most CA cities) | Yes — with owner-occupancy requirement |
| Typical cost | $90,000–$350,000+ | $40,000–$120,000 |
| Rental income potential | $2,200–$5,000/month | $1,500–$2,800/month (smaller unit) |
Can You Build Both an ADU and a JADU?
Yes! California law (AB 68) allows a single-family property to have both a JADU (within the primary home) AND one detached ADU simultaneously. This means you could theoretically have 3 units on a single-family lot: the primary home, a JADU carved out of part of the home, and a detached ADU in the backyard. This is a powerful income-generating strategy for San Jose homeowners.
Which Is Right for You?
- Choose ADU if you want maximum rental income, a fully independent unit for a family member, or you have space for a detached structure
- Choose JADU if your lot is small, you want to minimize construction cost, you’re converting unused interior space (unused bedroom, bonus room), or you want a lower-cost start with maximum flexibility
Quartz Construction builds both ADUs and JADUs throughout San Jose and the Bay Area. Learn more about ADU construction. CSLB #1003436 | BBB A+ | 4.9⭐. Call (650) 749-7436 for a free feasibility consultation.
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What Our Bay Area Clients Say
4.9 ★ average rating across Google, Yelp, and Houzz from 150+ Bay Area homeowners.
"Quartz Construction did an amazing job on our kitchen remodel. The team was professional, on time, and the results exceeded our expectations. Highly recommend to any Bay Area homeowner!"
— Michael T. |
"We hired them for a bathroom remodel in our San Jose home. From permitting to final walkthrough, everything was handled perfectly. The tile work is stunning. 5 stars without hesitation."
— Sarah L. |
"Just finished our ADU garage conversion. The project came in on budget and on schedule — rare in the Bay Area! The rental income already started. Could not be happier with Quartz Construction."
— David R. |
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