Accessory Dwelling Units (ADUs) are a popular way for San Diego homeowners to add value, create rental income, or provide flexible living space. However, local regulations can be complex. Below is a comprehensive overview of the current rules and requirements for building an ADU in the City of San Diego.
Key ADU Rules
- Maximum Size: Up to 1,200 square feet for both attached and detached ADUs.
- Setbacks: Side and rear setbacks can be as little as 0 feet for ADUs up to 16 feet tall; 4 feet is recommended and required for two-story units or those exceeding 16 feet in height.
- Building Separation: Minimum of 6 feet between detached structures on the same lot.
- Stories: Two-story ADUs are allowed, subject to height and setback requirements.
- Height Limits: Detached ADUs can be at least 16 feet tall; maximum height is determined by the underlying residential zoning, typically between 24 and 30 feet.
How Many ADUs Can You Build in San Diego?
Single-Family Lots:
- One detached or attached ADU (up to 1,200 sq ft)
- One Junior ADU (JADU), created from existing space within the main home, up to 500 sq ft
- Additional affordable and bonus ADUs may be allowed, especially in transit priority areas, subject to zoning and lot coverage requirements.
Multi-Family Properties:
- Up to two detached ADUs, even if only one house exists on the lot
- For properties with multiple existing units, as many detached ADUs as there are existing units, up to a maximum of eight (effective January 2025, per new state law)
- Unlimited conversion of non-livable spaces (e.g., storage rooms, garages) into ADUs, in addition to the above
Types of ADUs Allowed
- Detached: Separate structure from the main home
- Attached: Shares at least one wall with the main home
- Conversion: Transforming existing non-livable space (garage, basement, storage) into an ADU
- Junior ADU (JADU): Up to 500 sq ft, created from existing space within the main home, with its own entrance and efficiency kitchen
Size, Height, and Setback Requirements
- Maximum Size: Both attached and detached ADUs may be up to 1,200 sq ft, regardless of the size of the main home7.
- Height: Detached ADUs can be at least 16 feet tall; taller structures are allowed if they comply with underlying zoning (typically up to 24–30 feet).
- Setbacks:
- 0 feet side/rear for ADUs up to 16 feet tall
- 4 feet side/rear for two-story or taller ADUs, or if the lot abuts another residential property
- Street-side setbacks follow the underlying zoning
- Minimum 6 feet separation between detached structures on the same lot.
- Fire Safety: If building within 5 feet of a property line, fire-rated construction is required, which may increase costs.
Special Zoning Considerations
- Coastal Zone: ADUs in the coastal overlay zone require a coastal development permit and must comply with additional regulations to protect coastal resources.
- Transit Priority Areas: Bonus and affordable ADUs may be allowed, and parking requirements are further relaxed.
- Historic Districts & High Fire Zones: Additional restrictions may apply; consult with city planning for specifics.
Parking Requirements
- General Rule: No parking is required for ADUs outside the Coastal Overlay Zone.
- Coastal Overlay Zone: Parking may be required unless the ADU is under 500 sq ft, in a historic district, or meets other specific exemptions.
- Replacement Parking: Not required if a garage or carport is converted to an ADU, except in certain coastal areas.
- Location: If required, parking may be tandem or within setbacks.
Permitting Process
- Digital Plan Submission: San Diego accepts electronic applications for ADU permits.
- Plan Check: The city reviews plans for compliance with zoning, building, and safety codes. Plan check fees typically range from $1,500–$2,500, and the first review may take up to 60 days.
- Corrections & Resubmittal: Any required changes are addressed and plans resubmitted; subsequent reviews usually take about 30 days.
- Permit Issuance: Once approved, additional fees are paid and the building permit is issued.
- Inspections: Routine inspections occur throughout construction to ensure compliance before final sign-off.
Additional Requirements
- Landscaping: For properties with two or more ADUs/JADUs, two trees must be planted per 5,000 sq ft of lot area (minimum one tree per property), following city guidelines.
- Exterior Design: While there are no strict requirements, it’s recommended that ADUs match the primary home’s exterior materials and color palette.
- Guest Quarters: Allowed in addition to ADUs and JADUs, but cannot be rented or sold separately and may not have full kitchens.
Frequently Asked Questions
Can you build an ADU in the front yard?
Yes, as long as it meets front setback requirements or, if not possible elsewhere, state law allows at least an 800 sq ft ADU even if it encroaches into the front setback.
Are two-story ADUs allowed?
Yes, two-story ADUs are permitted, but must comply with height and setback rules. Stairs must generally be at least 5 feet from the property line.
Is a soils report required?
No, soils reports are not required for ADUs in San Diego7.
Are roof decks allowed on ADUs?
Yes, as long as they comply with height and setback requirements. Railings and staircases above 42 inches are included in height calculations.
San Diego offers flexible options for building ADUs, with generous size limits, relaxed parking requirements, and the ability to add multiple units in some cases. However, each property is unique, and regulations can change. For the most accurate guidance and to ensure your project runs smoothly, consult with a local ADU builder familiar with the latest city and state requirements.
Ready to explore your ADU options? Contact our team for a consultation and let us guide you through every step of the process.
References:
https://www.sandiegocounty.gov/content/dam/sdc/pds/bldg/adu_info/COSD_ADU_Handbook.pdf
https://www.sandiego.gov/planning/work/housing/toolkit/accessory-dwelling-units