ADU Rules: Bostonia vs San Diego
How do adu rules rules compare between Bostonia, CA and San Diego, CA?
Bostonia has fewer restrictions than San Diego.
Bostonia, CA
San Diego County
Bostonia is an unincorporated CDP in San Diego County (adjacent to El Cajon) governed by the San Diego County Zoning Ordinance §6156 (Accessory Dwelling Units and Junior Accessory Dwelling Units), not a city ordinance. The County allows one ADU plus one JADU on single-family lots; non-conforming multifamily complexes may have up to two detached ADUs OR conversion ADUs created within the existing complex.
View full Bostonia 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 | Bostonia | San Diego |
|---|---|---|
| Governing Code | San Diego Co. Zoning Ord. §6156 | - |
| Max Attached ADU | 1,200 sq ft (50% rule applies) | - |
| Max Detached ADU | 1,200 sq ft | 1,200 sq ft |
| Max JADU | 500 sq ft | - |
| Side/Rear Setback | 4 ft minimum + fire setbacks | - |
| 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.
Bostonia FAQ
Who regulates ADUs in Bostonia?
Bostonia is unincorporated San Diego County, so the San Diego County Department of Planning & Development Services regulates ADUs under Zoning Ordinance §6156, not the City of El Cajon.
How big can my Bostonia ADU be?
Under §6156, detached ADUs may be up to 1,200 sq ft and attached ADUs up to 50% of the primary dwelling capped at 1,200 sq ft (at least 800 sq ft must always be allowed). JADUs are capped at 500 sq ft within the existing single-family dwelling.
Can a Bostonia multifamily complex add ADUs?
Yes, but only one approach per property: up to two detached ADUs OR conversion ADUs created within the existing multifamily complex, not both, per §6156.
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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