California changes rules on Accessory Dwelling Units (ADUs)

Adding additional living space to your property is now easier! Build a space for grandma or supplement your mortgage with rental income.

The California  legislature  recently passed several  laws paving the way for homeowners to add ADU’s. Under these new laws, the single term ADUs describe what in the past have been referred to as second units, granny flats, etc. Historically, each of these terms may have had a different definition, depending upon what city or county the property was located in. The definition of an accessory dwelling unit is now “an attached or detached residential dwelling unit which provides complete independent living facilities for one or more persons.

Another big benefit to homeowners is an increase in property value for homes with existing (or adding) an ADU. We are seeing a trend of buyers who are interested in purchasing properties which give them the option for multi-generation/family living.


What are the details you need to know.


  • Applicants for the ADU must be the owners/occupants of the property that is subject of the request, and the ADU must be used for rentals of terms longer than thirty days.
  • The permitted size of an ADU attached to an existing dwelling has been increased to 50 percent of the existing living area (up from 30 percent), with a maximum permitted increase in the floor area of 1200 square feet. ADUs that are in detached buildings may not exceed 1200 feet of floor space.
  • ADUs must still be consistent with local zoning laws and general plans regulating the density of lot development.
  • The laws provide for approval of ADUs in existing structures provided that certain requirements are met.
  • With respect to parking, the new laws state that only one space per ADU or bedroom may be required, and the parking space requirement under certain circumstances may be met by utilizing a setback space or as a result of tandem parking.
  • ADUs that are contained within existing structures are not to be considered new residential uses for purposes of calculating connection fees or capacity charges. With respect to ADUs that are not contained within an existing structure, local government may require new or separate utility connections, but those charges are to be proportionate to the burden of the proposed ADU on the water and sewage systems.

Interested in learning more?  Contact us to talk more about what these changes mean for you as a homeowner, for a potential purchase, or to start the process on building an ADU on your existing property.

Also, check out this memorandum from the California Department of Housing and Community Development