All ADU Regulations

South San Francisco, California

South San Francisco ADU municipal building codes were updated to comply with new state laws. Click for help navigating your build to fit local regulations.

September 13, 2020
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All properties zoned for single family and multifamily use may be eligible to build ADUs.

Number of units

The number of ADUs you’re able to build depends on how your lot is zoned:

  • Lots zoned for single family use may add 1 ADU and 1 Jr. ADU (JADU)
  • Lots zoned for multi-family may add up to 2 detached ADUs and 1 ADU per 4 existing residential units within an existing structure (e.g. garage conversion)

Building size

The maximum square footage you can build depends on your ADU type:

  • JADU: up to 500 sq. ft.; when an ADU is created within an existing accessory structure, an expansion of up to 150 sq. ft. to accommodate ingress and egress is allowed
  • Attached ADU: 800 sq. ft. or 50% of the floor area of the existing home, whichever is greater; maximum allowable area is 1,000 sq. ft.
  • Detached ADU: 1,000 sq. ft.

Building height

Detached ADUs can reach a maximum height of 16 feet. Attached ADUs can reach the same height as the main structure, assuming they comply with municipal code (including daylight plane).


Minimum setbacks of 4 feet from the side and rear lot lines, as well as 6 feet from any existing structures are required for detached ADUs.


No additional parking is required for ADUs if they are within 0.5 miles of public transportation (a bus stop, train station, etc.). When converting a garage or carport, replacement parking is not required.


Owner occupancy is not a requirement for permitting an ADU from January 1, 2020 until January 1, 2025. This is a great opportunity for rental property owners to increase their yields in a cost-effective way.


While long-term rentals are permitted for ADUs, homeowners may be required to sign a deed restriction preventing short-term rentals (e.g. Airbnb for less than 30 days).


Do you have a utility easement over your property? Do you have special setbacks? Reach out to us and we’ll help you build a custom ADU to fit your unique property characteristics and local regulations!

Design and build with confidence.