Palo Alto – ADU Regulations


All properties zoned for single family or multi-family with the following zoning codes are eligible for ADUs. Check the zoning of your property.

  • R-1 (most single family homes)
  • R-2, R-E, R-M, RMD (duplexes & multi-family)
  • OS (open space) when single-family residential is a permitted land use:
  • PC (planned community when single-family residential is a permitted land use:

Number of units

Lots zoned for single family use that have an existing dwelling are permitted to add 1 ADU and 1 Jr. ADU (JADU).

Building size

Minimum size of 150 square feet and maximum of 800 square feet, assuming that the main home is built to the lot’s floor coverage limit.

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 the underlying zoning district’s setbacks, including daylight plane requirements.


Basement space can be used for an ADU in the R-1 zoning district (and subdistricts).The square footage will not be included in the calculation of floor area for the entire site, as long as the measurement from first finished floor to grade around the perimeter of the building is no more than 3 feet.


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. Attached ADUs may be required to have 6 feet setbacks from side and rear lot lines.


No additional parking is required for ADUs. Even when converting a garage or carport, replacement parking is not required.

Should you decide you want to build additional parking, covered parking provided for the ADU is included in the total floor area for the site, but not included in determining the max size for the ADU.


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, short-term rentals (e.g. Airbnb) are not permitted in Palo Alto.