Accessory Dwelling Units (ADU)

On June 10, 2020, the City Council adopted a new ADU Ordinance, which went into effect on July 10, 2020.  The Code was amended to comply with new State laws intended to encourage the construction of ADUs by reducing regulatory barriers commonly found in local zoning ordinances, thereby making it easier for property owners to add an ADU and create new affordable housing units in the Town.


An ADU is an attached or detached residential dwelling unit that provides complete independent living facilities for one or more persons and is located on a lot with an existing primary residence.  ADUs are also referred to as second units or granny units.


Generally, an ADU falls into one of the following categories:

  • Detached

    • The unit is separate from the primary residence as either a newly constructed detached accessory structure or as the conversion of an existing detached accessory structure (i.e. detached garage).
  • Attached

    • The unit is attached to the primary residence as an integrated addition with an independent entrance.
  • Junior Accessory Dwelling Unit (JADU)

    • A unit that is up to 500 square feet in size and is contained entirely within an existing single-family structure. A JADU must have an efficiency kitchen and a separate exterior entrance, and may include separate sanitation facilities, or may share sanitation facilities with the primary residence.
  • Conversion of Existing Space

    • Floor area within the primary residence that is converted into an independent living unit.

Exceptions & Special Cases

  • Most ADU’s can be approved ministerially, without discretionary review or a hearing.
  • ADUs that are not larger than 800 square feet and compliant with general requirements may be constructed with only a building permit.
  • A manufactured home may be approved as an ADU.

Town Resources

Other ADU Resources


For additional information or assistance, please contact the Colma Planning Department at (650) 757-8888 or

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