Accessory Dwelling Unit Information and Resources 

San Mateo's ADU Ordinance (Zoning Code Chapter 27.19) establishes the development standards and requirements for ADUs and JADUs, and is aligned with all applicable State laws. The approval process for a compliant ADU or JADU is ministerial, with only a building permit and related permits required. A planning application with public notification is not required.  

What is an Accessory Dwelling Unit?


An Accessory Dwelling Unit (ADU) is accessory to a primary residence and has complete independent living facilities for one or more persons. An ADU can be attached or detached from the primary dwelling unit, or converted from existing floor area. It is required to provide permanent provisions for living, sleeping, eating, cooking facilities, and sanitation, and 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?


A Junior Accessory Dwelling Unit (JADU) is an additional, independent living unit created through conversion of existing floor area in a single-family residential dwelling unit.

Note: An Accessory Dwelling Unit is different from an Accessory Building.  An Accessory Building includes garden sheds, tool sheds, workshops, and garden sheds, per 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 Trees – learn about the requirements for Heritage Tree preservation.
  4. ADU/JADU Permit Fees 
    • Accessory Dwelling Unit (new) - $2,671.39 (per unit/flat fee)
    • Accessory Dwelling Unit (remodel) - $1,916.15 (per unit/flat fee) 
    • Junior Accessory Dwelling Unit - $1,371.72 (per unit/flat fee)
    • View the Comprehensive Fee Schedule
  5. ADU/JADU Standards and Requirements:
  6. Additional Resources:

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
Email: planning@cityofsanmateo.org

Building Division
Phone: (650) 522-7172
Email: building.info@cityofsanmateo.org

Public Works Department
Phone: (650) 522-7301
Email: publicworks@cityofsanmateo.org

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