ADU Rules: Fallbrook vs San Diego
How do adu rules rules compare between Fallbrook, CA and San Diego, CA?
Fallbrook and San Diego have similar restriction levels.
Fallbrook, CA
San Diego County
San Diego County allows Accessory Dwelling Units (ADUs) on residential properties in unincorporated areas per state law and the County ADU Handbook. Detached ADUs up to 1,200 sq ft. Must maintain 4-foot side/rear setbacks. ADUs up to 800 sq ft are exempt from lot coverage limits.
View full Fallbrook rules →San Diego, CA
San Diego County
San Diego permits ADUs under SDMC Chapter 14, Article 1, Division 3, consistent with California ADU law (Government Code 65852.2). Single-family lots may have one ADU, one JADU, and one converted ADU. No owner-occupancy requirement. Permit timeline typically 3-5 months. SB 1211 (2024) allows up to 8 ADUs.
View full San Diego rules →Key Facts Comparison
| Fact | Fallbrook | San Diego |
|---|---|---|
| Max Size (Detached) | 1,200 sq ft | - |
| Side/Rear Setback | 4 feet minimum | - |
| Lot Coverage Exempt | ADUs up to 800 sq ft | - |
| Height (at property line) | 16 ft max, else 4 ft setback | - |
| Separation | 6 ft from other structures | - |
| Max Detached ADU | - | 1,200 sq ft |
| JADU Size | - | 150-500 sq ft |
| Rear/Side Setback | - | 4 feet |
| Parking | - | Not required |
| SB 1211 (2025) | - | Up to 8 ADUs |
Highlighted rows indicate differences between cities.
Fallbrook FAQ
Can I build an ADU in unincorporated San Diego County?
Yes. State law requires the County to allow ADUs on residential properties. Detached ADUs up to 1,200 sq ft are permitted with a building permit from County PDS.
What are the setback requirements for an ADU?
Both attached and detached ADUs must maintain at least 4-foot side and rear setbacks. Detached ADUs 16 feet tall or less may be at the property line. Front setbacks follow the underlying zone.
Does an ADU count toward lot coverage?
ADUs up to 800 sq ft are exempt from lot coverage requirements, meaning you can build one even if your lot is at the maximum allowed coverage.
San Diego FAQ
How many ADUs can I build in San Diego?
On a single-family lot: one ADU, one JADU, and one converted ADU. SB 1211 (effective January 2025) expands this to up to 8 ADUs on qualifying lots.
Do I need to live on the property to build an ADU?
No owner-occupancy requirement for ADUs under California state law. JADUs require owner-occupancy of either the primary unit or the JADU.
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