Accessory Dwelling Units

Accessory Dwelling Unit

Accessory dwelling units (ADUs) are also known as second units, granny units, in-law suites, or carriage houses. Within Cotati, nearly every residential property is eligible to construct an ADU.

ADUs can come in many shapes and sizes but an ADU is always a self-contained home that is smaller than the main house and legally part of the same property. There are many different types of ADUs, but they generally fall into one of the following categories: interior or garage conversions; detached stand-alone ADUs, ADUs attached to the primary residence, and ADUs constructed above garages.

ADU Types

  • Detached: free-standing structure, such as a backyard cottage
  • Attached: shares at least one wall with the primary home
  • Interior Conversion: built from existing converted space (e.g, attic or a basement
  • Garage Apartment: converted former garage space
  • Above Garage: unit built above garage 

In addition to an ADU, nearly every single-family residential property is also eligible to construct a Junior ADU (JADU).  JADUs generally follow these guidelines:

  • Located within the walls of an existing or proposed single-family residence
  • Maximum size 500 square feet
  • Separate exterior entrance
  • Efficiency kitchen: sink, cooking appliance, counter surface and storage
  • May share a bathroom with primary residence

Need help to plan and build your ADU? Check out these resources:
To support ADU and JADU development, the City of Cotati has partnered the Napa Sonoma ADU Center to provide resources to homeowners considering construction of an ADU or JADU. Explore their website to find useful resources such as different floor plans, an ADU Handbook, helpful webinars, an ADU calculator, and stories from people that have built their ADU.  

Homes for Sonoma is a nonprofit developer creating quality workforce housing options that support a safe and sustainable community. Founded to create affordable housing options in the immediate aftermath of the 2017 fires, the organization has since expanded its mission to find efficient, scalable solutions to address the housing crisis in Sonoma County and throughout California with an emphasis on accessory dwelling units (ADUs).



Learn from your neighbors.

  • Contact Info
  • Community DevelopmentJP Harries 
  • Address201 West Sierra Ave., Cotati 
  • Telephone707-665-3634 
  • Email