San Bernardino County is very ADU-friendly with no parking requirements and a 60-day approval mandate. Both County and City paths available. Favorable zoning in most residential areas with low restrictions.
Zoning & Size Requirements [1]
| Allowed Zones | Most residential zones (R-1, R-2, R-3, multifamily) |
| Max Size (Detached) | 1200 sq ft; reduces to 800 sq ft if lot coverage exceeded |
| Max Size (Attached) | 1200 sq ft or 50% of primary dwelling, whichever is less |
| Max Size (JADU) | 500 sq ft |
| Max Height | 16 ft minimum; up to 25 ft with exceptions |
| Max Units | 1 ADU + 1 JADU per single-family lot; 2 ADUs on multifamily |
Setback Requirements [1]
| Rear Setback | 4 ft minimum (detached new construction) |
| Side Setback | 4 ft minimum (interior side, detached new construction) |
| Front Setback | Base zone compliance |
| Parking Required | No additional parking required (conversions/existing exempt) |
| Owner Occupancy | Not required under state law |
| Min Lot Size | No specific state minimum |
Permit Process & Fees [2]
| Approval Process | County ADU Handout provides detailed requirements. Submit to San Bernardino County Land Use Services. |
| Review Timeline | 60 days mandatory for approval/denial of complete applications with existing dwelling |
| Permit Fees | $3,000-$12,000 estimated (varies by jurisdiction within County) |
| Impact Fees | Waived under 750 sq ft (SB 13); proportional for larger units |
| Plan Check | Included in permit timeline; County must respond within 60 days |
| Pre-Approved Plans | County has standard ADU plans available |
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Construction Costs
| Average Build Cost | $160,000-$280,000 |
| Cost per Sq Ft | $200-$260 |
| Garage Conversion | $75,000-$140,000 |
| Prefab ADU (Installed) | $80,000-$150,000 |
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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
| Avg Rent (1 Bedroom) | $1,300-$1,700 |
| Avg Rent (2 Bedroom) | $1,700-$2,100 |
| Short-Term Rental | Subject to city/county ordinances; verify before planning |
| Est. Annual ROI | 7-10 year payback |
Explore Prefab ADU Options
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 13 impact fee waivers for <750 sq ft units
- County mandates 60-day approval timeline
- ADU Handout (updated) clarifies regulations
- CALHFA $40,000 ADU grant funds available for County residents
Tips for Building an ADU in San Bernardino
- County is very supportive of ADU development
- 60-day approval timeline is legally mandated
- Check if property qualifies for CALHFA $40,000 grant
- No parking requirements reduce construction costs
- Contact County Land Use Services for specific property questions
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- San Bernardino Planning Department — ADU Information Planning Department — Accessed 2026-03-15
- San Bernardino Building Department — Permit Information building_dept — Accessed 2026-03-15
Frequently Asked Questions
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