ADU rules in Bostonia, CA — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
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.
San Diego County Zoning Ordinance §6156.x implements California Government Code §65852.2 with ministerial review without a public hearing. Attached ADUs are limited to 50% of the primary single-family dwelling's floor area up to 1,200 sq ft (with at least 800 sq ft allowed regardless of the 50% rule); detached ADUs may be up to 1,200 sq ft. JADUs are capped at 500 sq ft within the walls of the primary single-family dwelling. All newly constructed ADUs must meet a 4-foot minimum side and rear setback (plus any required fire setbacks); front and exterior side yard setbacks follow the underlying zone. One parking space is required per ADU, may be located in tandem in an existing driveway, and is waived where the property is within a half-mile of transit or another state exemption applies. On non-conforming multifamily complexes, owners may add up to two detached ADUs OR conversion ADUs in existing space — but not both — per §6156.
Unpermitted ADUs in unincorporated Bostonia are violations of the San Diego County Zoning Ordinance and Building Code, enforced by San Diego County Code Compliance with stop-work orders, daily-accruing fines, and required after-the-fact permitting or removal. Failing to record the JADU owner-occupancy deed restriction blocks final inspection.
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Side-by-side rule comparisons with other cities in San Diego County.
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