San Diego ADU Setback Rules 2026
Everything you need to know about building setbacks for ADUs in San Diego
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San Diego has adopted progressive ADU regulations that align with California state law (SB 9, AB 68, AB 2097). Setback requirements for ADUs are significantly reduced compared to primary structures, making it easier to add density on existing residential lots. This guide covers the current rules as of 2026.
Key Facts at a Glance
Min Side Setback (Detached ADU)
4 ft
Min Rear Setback (Detached ADU)
4 ft
Front Setback
Per underlying zone (typically 15 ft)
Max ADU Size (Detached)
1,200 sq ft
Max Height (Detached ADU)
16 ft (or 18 ft with roof pitch)
Garage Conversion Setback
Exempt
Standard ADU Setbacks
For detached ADUs in San Diego, the minimum setback is 4 feet from both the side and rear property lines. This applies to structures up to 16 feet in height. Front setbacks follow the underlying zone requirements (typically 15 feet in RS zones). Under state law, local jurisdictions cannot impose setbacks greater than 4 feet for detached ADUs that are 800 sq ft or less and 16 feet or less in height.
Attached ADU Setbacks
Attached ADUs (converted from existing space or additions to the primary dwelling) must comply with the setback requirements of the primary structure — typically 15 ft front, 4-5 ft side, and 13 ft rear in RS-1-7 zones. However, if converting existing legally-permitted space (e.g., a garage), no additional setbacks are required regardless of current setback compliance.
Garage Conversion Exemptions
Converting an existing garage to an ADU does not require setback compliance, even if the garage is built to the property line (0 ft setback). This exemption applies to any legally-built structure being converted. Replacement parking is not required for garage conversions within a Transit Priority Area or within ½ mile of a high-quality transit corridor.
Coastal Overlay Zone Considerations
Properties within San Diego's Coastal Overlay Zone may be subject to additional setback requirements under the Local Coastal Program. However, the California Coastal Commission has issued guidance that ADU construction should generally be approved consistent with state ADU law. Consult with the Development Services Department for specific parcels.
Frequently Asked Questions
Can I build an ADU with a 4-foot setback from the rear property line?
Yes. Under both California state law and San Diego municipal code, detached ADUs up to 16 feet in height require only a 4-foot rear and side setback.
Do setback rules apply if I convert my garage to an ADU?
No. Converting existing legally-built space is exempt from setback requirements, even if the structure is at the property line.
Are ADU setbacks different in the Coastal Zone?
Potentially. The Coastal Overlay Zone may impose additional requirements, but the Coastal Commission generally supports state ADU law compliance. Check your specific parcel.
Citations & References
- SDMC §141.0302 – Accessory Dwelling Unit Regulations
- California Government Code §65852.2(a)(1)(D)
- SDMC §131.0461 – RS Zone Development Regulations
- California AB 68 (2019) – ADU Reform
- San Diego Development Services Information Bulletin 531
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