ADU Rules: Bonsall vs San Marcos
How do adu rules rules compare between Bonsall, CA and San Marcos, CA?
Bonsall and San Marcos have similar restriction levels.
Bonsall, 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 Bonsall rules →San Marcos, CA
San Diego County
San Marcos allows one ADU plus one JADU per single-family lot per SMMC Chapter 20.410.060. One-bedroom ADUs up to 850 sq ft, two-bedroom up to 1,000 sq ft. ADUs generally cannot be in the front yard. A soils report is required over 500 sq ft.
View full San Marcos rules →Key Facts Comparison
| Fact | Bonsall | San Marcos |
|---|---|---|
| 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 | - |
| 1 BR Max | - | 850 sq ft |
| 2+ BR Max | - | 1,000 sq ft |
| Front Yard | - | Generally prohibited |
| Soils Report | - | Required over 500 sq ft |
Highlighted rows indicate differences between cities.
Bonsall 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 Marcos FAQ
Can I build an ADU on my property in San Marcos?
San Marcos allows one ADU plus one JADU per single-family lot per SMMC Chapter 20.410.060. One-bedroom ADUs up to 850 sq ft, two-bedroom up to 1,000 sq ft. ADUs generally cannot be in the front yard. A soils report is required over 500 sq ft.
What are the size limits for an accessory dwelling unit in San Marcos?
1 BR Max: 850 sq ft. 2+ BR Max: 1,000 sq ft. Front Yard: Generally prohibited. Soils Report: Required over 500 sq ft.
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