San Diego ADU Code Review 2025

By Sean Canning

At Ten Seventy Architecture, we stay closely informed about San Diego's evolving accessory dwelling unit (ADU) regulations. Since their introduction in 2020, I've seen these regulations change dramatically, and understanding these updates is essential for property owners, developers, and architects. As the principal architect at Ten Seventy Architecture, I've designed and permitted over 50 ADUs, gaining substantial expertise in this area. Here's a comprehensive overview of the latest municipal code updates from February 2025, along with practical insights I've gathered through my experience.

Understanding ADUs and JADUs

Accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) give homeowners flexible options to add extra living spaces. ADUs are independent units complete with kitchens and bathrooms, while JADUs are smaller (up to 500 square feet), located within or attached to a primary residence, and typically require owner occupancy.

ADU Permitting Basics

ADUs and JADUs can be built in any San Diego zone permitting residential use. Single-family zones allow one ADU and one JADU per property, while multifamily zones typically permit two detached or attached ADUs plus additional conversions from spaces like garages or basements.

Importantly, these units must be rented out for at least 31 consecutive days, effectively eliminating the possibility of short-term rentals like Airbnb.

Setback and Size Requirements

Setback requirements depend on the height of your ADU:

  • Single-story ADUs under 16 feet require no side or rear setbacks.
  • ADUs taller than 16 feet or two-story ADUs require at least a four-foot setback from property lines.

The size limitations range from a minimum of 150 square feet to a maximum of 1,200 square feet. Notably, one ADU up to 800 square feet is always allowed, even if your property has reached the maximum floor area ratio (FAR), offering significant flexibility.

Floor Area Ratio (FAR) and Density

ADUs and JADUs don’t affect your property’s density limits but do count toward the total FAR. Thus, while you may exceed the usual limit on units, you can't exceed the lot’s FAR unless utilizing the special provision permitting one 800 square foot ADU beyond the FAR.

Existing Structures and Conversions

San Diego’s regulations greatly favor converting existing structures:

  • Existing structures can maintain current setbacks if converted into an ADU.
  • There’s no limit to ADUs created from non-habitable spaces.

However, adding more than 150 square feet for entrances negates these benefits, so careful planning is essential.

Parking Requirements

Generally, no additional parking is required for ADUs or JADUs, removing a significant barrier to construction. Exceptions exist for specific beach or parking impact zones outside transit priority areas, where one off-street parking space might be necessary.

Development Fees and Impact Costs

San Diego provides notable fee incentives for ADUs:

  • The first two ADUs have no development impact fees.
  • Additional ADUs under 750 square feet remain fee-exempt, while larger ADUs incur prorated impact fees.

Despite these incentives, developing ADUs remains costly due to land prices, construction materials, and labor.

Affordable Housing and Accessibility Bonuses

San Diego’s ADU Bonus Program currently allows unlimited ADUs in sustainable development areas, matched one-to-one with affordable units. However, this incentive is under review by the city council, potentially facing substantial changes or repeal.

Additionally, an accessibility bonus allows an extra ADU if you include units compliant with ADA standards. Eliminating or reducing this bonus could unintentionally reduce accessible housing options.

Junior Accessory Dwelling Units (JADUs)

JADUs have stricter limitations:

  • Owner occupancy is required.
  • Size ranges from 150 to 500 square feet.
  • Must be within or attached to the primary dwelling.

Due to these constraints, I typically recommend traditional ADUs over JADUs unless owner occupancy is not an issue.

Practical Advice from Ten Seventy Architecture

Based on extensive experience, here are several recommendations for successful ADU projects:

  • Provide off-street parking whenever possible to significantly boost rental value.
  • Be cautious about driveway configurations; losing driveway access can result in substantial additional costs.
  • Detached ADUs generally offer better privacy and rental potential.
  • Converting existing structures, especially garages, typically provides the most cost-effective path due to favorable setbacks and regulations.

Conclusion

San Diego’s ADU regulations, while complex, present excellent opportunities for maximizing property value, addressing housing shortages, and achieving financial goals. Stay informed about ongoing changes and carefully plan your ADU developments to fully leverage current incentives.

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