Thank you for joining the Planning Commission for the Accessory Dwelling Unit Study Session on October 7, 2019.

 Front of ADU

Photo by: Second Unit Center

 What is an Accessory Dwelling Unit (ADU)?

ADUs (Accessory Dwelling Units), also known as granny flats or in-law units, provide independent living quarters for one household with full facilities for sleeping, eating, cooking, and sanitation on the same lot as the primary single-family dwelling. The ADU may be attached, detached, or located within the living areas of the primary dwelling unit on the lot.

Examples of ADUs include:

  • Detached: The ADU structure is detached from the primary dwelling unit
  • Attached: The ADU structure is attached to the primary dwelling unit
  • Converted: The ADU within the existing primary dwelling unit or the ADU was established through conversion of an accessory structure (i.e. garage or pool house)


  • ADUs can provide a source of income for homeowners
  • ADUs give homeowners the flexibility to create a home to share with family members and others, allowing seniors to age in place as they require more care
  • ADUs are a different form of housing that can help San Carlos meet its diverse housing needs
  • ADUs are a critical form of infill-development that can be affordable and offer additional housing opportunities within existing neighborhoods
  • ADUs are an affordable type of home to construct because they do not require paying for land, major new infrastructure, structured parking, or elevators. 

Reason for the ADU Update:

In response to the Bay Area’s regional housing shortages, Governor Brown signed new laws (SB 1069 and AB 2299) from 2016 to 2018 to encourage the construction of more ADUs by reducing the regulatory barriers commonly found in local zoning ordinances. To comply with the updated state policies, the City of San Carlos is undergoing a process of updating its local ADU Ordinance (currently titled Second Dwelling Unit in the City’s municipal code).

Study Session Details:

Many members of the community attended in response to extensive outreach. Staff updated the Commission on recent laws that will be going into effect as of January 1, 2020. In addition, staff presented recommendations on specific ADU policies. The Commission directed staff to work on the following items:

1) Create specific definitions and building code language for kitchens, bathrooms, and cooking facilities.

2) Prepare exhibits showing the possibilities of maximum single-family floor area with ADUs.

3) Draft a summary of existing vs. new parking requirements.

4) List the impacts of state law on properties within the Hillside Overlay District and adjacent to creeks.

5) Provide information on possible incentives (other than an increase in floor area) to encourage affordable units.

6) Meet with the Transportation and Circulation Commission for feedback.         

7) Determine if Junior ADUs have to be allowed in San Carlos.

Community Development staff is currently working on these items and will return to the Planning Commission with a draft ordinance within the next few months, which will be forwarded to the City Council for consideration in Winter/Spring 2020.

Summary of New State Requirements:

Fire Requirements
ADUs within Existing Spaces such as Primary Dwelling, Garage, Pool House, Etc.
Approval Process