Quick Answer: A Junior ADU (JADU) is a unit of up to 500 sq ft created within the existing walls of a single-family home, with its own private entrance and at least an efficiency kitchen. A standard ADU (Accessory Dwelling Unit) can be up to 1,200 sq ft and can be built as a completely new structure (detached) or an addition to the existing home. Key differences: JADUs require owner-occupancy of either unit; ADUs do not (as of 2020). JADUs have no setback requirements; ADUs must be at least 4 feet from side and rear property lines.
JADU vs ADU Comparison — California 2025
Helpful Resources:
| Feature | JADU (Junior ADU) | ADU (Standard ADU) |
|---|---|---|
| Maximum size | 500 sq ft | 1,200 sq ft (detached); 50% of main home (attached) |
| Location | Within existing home footprint only | Can be new structure, addition, or conversion |
| Kitchen requirement | Efficiency kitchen (not full) allowed | Full kitchen required |
| Bathroom requirement | Can share bathroom with main house | Private bathroom required |
| Separate entrance | Required — separate exterior door | Required |
| Setback from property line | None (uses existing structure footprint) | 4 feet from side and rear lot lines minimum |
| Owner-occupancy required? | Yes — owner must live in JADU or main house | No — California eliminated this requirement in 2020 |
| Permits and fees | Lower — no impact fees allowed by California law | Impact fees may apply for units over 750 sq ft |
| Cost to build | $40,000 – $120,000 | $90,000 – $500,000+ depending on type and size |
| Rental income potential | $1,800 – $2,800/month | $2,500 – $5,000+/month |
When Should I Build a JADU vs an ADU?
- Build a JADU when: You have existing interior space you want to convert (e.g., a large room with exterior access, an attached garage), you don’t have room in the backyard for a new structure, or your lot constraints (setbacks, lot coverage limits) prevent a detached ADU. JADUs are also faster to permit and build since no new foundation is required
- Build a standard ADU when: You have backyard space, you want maximum rental income (larger unit = higher rent), you want complete privacy from tenants, or you want the maximum property value increase. A detached ADU adds more value ($200,000–$400,000) than a JADU ($80,000–$150,000) in most Bay Area markets
Quartz Construction builds both JADUs and standard ADUs throughout San Jose and the Bay Area. Call for a free ADU/JADU feasibility consultation: (650) 749-7436. Learn about ADU construction. CSLB #1003436.
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"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."
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"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."
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