Accessory Dwelling Unit (ADU) & Junior Accessory Dwelling Unit (JADU)

The City of San Mateo has developed materials consistent with the most recent State Law changes (SB 13, AB 68 and AB 881) pertaining to Accessory Dwelling Units and Junior Accessory Dwelling Units.
This legislation is effective as of January 1, 2020. 

This page summarizes key Planning, Building, Fire, and Public Works requirements.

Note: The requirements summarized below are not inclusive. If you have specific questions for your project, please contact the appropriate department. 

What is an Accessory Dwelling Unit (ADU)?

An Accessory Dwelling Unit, also known as a granny or in-law unit, is a smaller living unit. An ADU is an attached or detached residential dwelling unit which provides independent living facilities for one or more persons.  The ADU unit is located on the same property as the primary residence, is accessory to the primary residential building and is required to be smaller than the primary residence.  

An ADU is required to provide permanent provisions for living, sleeping, eating, cooking facilities, and sanitation, as well as, meet other requirements as stipulated by applicable life and safety code requirements from the Building Division, Fire and Public Works Departments. 

What is an Junior Accessory Dwelling Unit (JADU)?

A Junior Accessory Dwelling Unit (JADU) is an additional, independent living unit created through the conversion of an existing legally permitted bedroom in a single-family dwelling.

Note: An Accessory Dwelling Unit is different from an Accessory Building.  An Accessory Building, or structure, includes garden sheds, tool sheds, workshops, and garden sheds. SMMC: Chapter 27.70
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Can I add an ADU/JADU to my property?

Ready to get started?

  1. Find your zoning district - use our interactive Property Zone Look-Up Tool (interactive GIS map) or check the Zoning Map (.pdf)
  2. FEMA Flood Zone Map – find out if your property is located in the FEMA flood zone.
  3. Heritage Tree – learn about the requirements for Heritage Tree preservation.
  4. ADU/JADU Development Fees - effective July 1, 2020 to June 30, 2021
  5. Download related documents:
  6. Additional Resources:

ALSO SEE: Accessory Dwelling Unit (ADU) & Junior Accessory Dwelling Unit (JADU) Ordinance Update

Contact Us 

Building, Fire, Planning, & Public Works
Code Consultation Counter Hours:

Monday - Friday, 9:30 am - 11:30 am

Planning Counter Closed Every Tuesday from 9:00 am - 12:30 pm

Planning Division
Phone: (650) 522-7212

Building Division
Phone: (650) 522-7172

Public Works Department
Phone: (650) 522-7301

San Mateo Consolidated Fire
Phone: (650) 522-7940