Understanding San Diego's New ADU Regulations

On June 16, 2025, the San Diego City Council approved considerable changes to the city's ADU program that will significantly impact some property owners. If you're considering building ADUs, here are just a few key things to know about the new regulations. 

Major Changes: What's New vs. What Was 

Attached, Detached, or Conversions?

• Single Family Lots = one ADU is allowed within the main dwelling unit or accessory structure and one attached or detached ADU is allowed
• Existing Multiple Dwelling Units = non-livable space can be converted into ADUs, up to 25% of the existing multiple dwelling units or minimum of 1, and 8 detached ADUs are allowed
• Proposed Multiple Dwelling Units = 2 ADUs are allowed, must be detached

Previously, both livable and non-livable space in multiple dwelling unit structures could be converted, new ADUs could be attached to the structure, and more than 2 new ADUs would only be possible with the designation of some units as affordable housing. 

Unit Caps for Single Dwelling Unit Lots – Perhaps the Biggest Change

• Properties under 6,000 sq ft: 4 total ADUs/JADUs maximum
• Properties 6,000-6,999 sq ft: 5 maximum
• Properties 7,000-7,999 sq ft: 6 maximum
• Properties 8,000+ sq ft: 7 maximum

Previously, there were no caps within Transit Priority Areas—property owners could build unlimited bonus ADUs by providing affordable units.  

New Fire Safety Requirements

• 4-foot minimum setbacks required for ADUs in High and Very High Fire Hazard Severity Zones
• Automatic fire sprinkler systems are required for all affordable and bonus ADUs
• Fire Code Official can require greater setbacks when necessary
• Within the High and Very High Fire Hazard Severity Zones, lots must front on public streets, which have 2 evacuation routes (cul-de-sacs and neighborhoods with one entrance road will not comply)

Previously, zero-foot setbacks were allowed, and sprinklers were only required if the primary dwelling had them. 

Parking Requirements

• One parking space required per affordable and bonus ADU located outside Transit Priority Areas
• Must be provided on-site in hardscape areas

Previously, generally no parking was required for ADUs/JADUs. 

Zone Exclusions

• ADU Home Density Bonus Program is now prohibited in RS-1-1 through RS-1-4 and RS-1-8 through RS-1-11 zones
• Exception: Properties in High/Highest CTCAC Opportunity Areas remain eligible

Previously, the program was available in all zones allowing residential uses.  

Development Scale Controls

• Floor Area Ratio calculations are capped at 8,000 sq ft for single-family lots
• $10,000 per ADU per month penalty for violating affordable housing deed restrictions
• Community Enhancement Fees are required for affordable and bonus ADUs 

New Opportunity: ADU Condominiums 

The regulations implement state Assembly Bill 1033, allowing ADUs to be sold as separate condominium units. Requirements include compliance with subdivision laws, lienholder consent, and a 30-day priority offering to owner-occupants. Rent-restricted affordable units cannot be sold during their deed restriction period. 

 When Do These Changes Take Effect?  

The ordinance requires Airport Land Use Commission review and a 30-day waiting period after final passage. Expected timeline: August 2025 for most areas, with Coastal Zone implementation potentially delayed until 2026. Projects with applications deemed complete before the effective date can proceed under current regulations. 

Implications for Property Owners

These regulations rebalance San Diego's ADU program, maintaining housing opportunities while addressing community concerns. Your property could be impacted positively or negatively by these changes. There are many other details within these changes that impact the design of an ADU project or a multiple ADU development. I am happy to discuss and evaluate how these regulations will impact you. 

Alex Miller

Licensed Architect

(858) 692-2529

alex@ama-arch.com  

This analysis is based on Ordinance O-2025-136 as approved by the San Diego City Council on June 16, 2025. Regulations may be subject to modification during the approval process. Always consult with qualified professionals and verify current regulations before beginning any development project.