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Accessory Dwelling Unit Information and Resources
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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Accessory Dwelling Unit (ADU) - Conversion of an accessory building
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Accessory Dwelling Unit (ADU) - Addition on-top of Garage
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Accessory Dwelling Unit (ADU) - Addition on-top of Garage
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Accessory Dwelling Unit (ADU) - A half-converted detached garage/pool house
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Accessory Dwelling Unit (ADU) - A half-converted detached garage/pool house
Ready to get started?
- Find your zoning district - use our interactive Property Zone Look-Up Tool (interactive GIS map) or check the Zoning Map (.pdf)
- FEMA Flood Zone Map – find out if your property is located in the FEMA flood zone.
- Heritage Tree – learn about the requirements for Heritage Tree preservation.
- ADU/JADU Development Fees - effective July 1, 2020 to June 30, 2021
- Accessory Dwelling Units - $2,734.00 (per unit/flat fee)
- Junior Accessory Dwelling Units - $1,237.00 (per unit/flat fee)
- View the Comprehensive Fee Schedule
- Download related documents:
- 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
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