San Jose has seen rapid ADU growth driven by Silicon Valley housing demand. The city follows CA state law closely and has added local incentives to encourage ADU construction.
Zoning & Size Requirements [1]
| Allowed Zones | All residential zones (R-1, R-2, R-M, R-MH) |
| Max Size (Detached) | 1,200 sq ft |
| Max Size (Attached) | 1,200 sq ft or 50% of primary dwelling |
| Max Size (JADU) | 500 sq ft |
| Max Height | 25 ft for detached |
| Max Units | 1 ADU + 1 JADU |
Setback Requirements [1]
| Rear Setback | 4 ft |
| Side Setback | 4 ft |
| Front Setback | Per underlying zone |
| Parking Required | No parking required |
| Owner Occupancy | Not required |
| Min Lot Size | No minimum |
Permit Process & Fees [2]
| Approval Process | Ministerial review |
| Review Timeline | 60 days |
| Permit Fees | $4,000-$14,000 |
| Impact Fees | Waived for units under 750 sq ft |
| Plan Check | Standard review process |
| Pre-Approved Plans | Limited pre-approved options available |
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Construction Costs [3][4]
| Average Build Cost | $180,000-$400,000 |
| Cost per Sq Ft | $250-$450 |
| Garage Conversion | $100,000-$220,000 |
| Prefab ADU (Installed) | $130,000-$300,000 |
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders.
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Rental Income Potential [5][6]
| Avg Rent (1 Bedroom) | $2,000-$2,800/mo |
| Avg Rent (2 Bedroom) | $2,500-$3,500/mo |
| Short-Term Rental | Restricted; requires transient occupancy tax registration |
| Est. Annual ROI | 5-9% annual return |
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Prefab ADUs can save 20-40% vs. traditional construction and cut build time in half.
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Recent Law Changes
What's Changed Recently
- SB 1211 in effect (2025-2026): Up to 8 detached ADUs allowed on multifamily lots statewide
- AB 1033 opt-in expanding (2026): More cities allowing separate sale of ADUs as condos
- Unpermitted ADU amnesty program extended through 2026 for retroactive permits
- New state-funded ADU grant program: Up to $40K for low-income homeowners (2026)
Tips for Building an ADU in San Jose
- Silicon Valley rents make ADUs extremely profitable despite high build costs
- Consider a prefab ADU to control costs in a high-cost labor market
- ADU rental income can significantly offset your mortgage in San Jose
- Check with the city's ADU resource center for the latest incentives
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Accessory Dwelling Units (ADUs) | City of San José Planning Department — Accessed 2026-02-24
- Preapproved ADUs | City of San José Planning Department — Accessed 2026-02-24
- HomeAdvisor — ADU Construction Cost Data Market Data — Accessed 2026-02-24
- Angi — Local ADU Contractor Costs Market Data — Accessed 2026-02-24
- Zillow Rental Manager — Market Rent Data Market Data — Accessed 2026-02-24
- HUD Fair Market Rents Government Data — Accessed 2026-02-24
- ADU Ordinance & Updates | City of San José Municipal Code — Accessed 2026-02-24
- California ADU Handbook — HCD Government Data — Accessed 2026-02-24
Frequently Asked Questions
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