ADU Building, Zoning, and Design Regulations for Sonoma, CA

With recent updates to California’s ADU laws, Sonoma is a great place to build an ADU and allows you to add significant value to your property. Before you start building, make sure you understand Sonoma’s special use regulations for accessory dwelling units.


Sonoma ADU Zoning Requirements

Zoning Regulations:

  • An ADU may be detached and on the same legal lot as a primary residence, attached to an existing primary residence or an existing/proposed accessory structure, or converted from a portion of the existing living area of the primary residence or existing accessory structure.
  • One (1) ADU is permitted on a lot that contains an existing or proposed single-family dwelling.
  • A lot that contains an existing multifamily dwelling may contain: Two (2) ADUs, detached from the multifamily structure, or up to 25% of the existing units in the multifamily dwelling, but at lease 1 converted from existing non-livable space in a multifamily structure.
  • One (1) ADU shall be permitted on a lot that contains a proposed multifamily dwelling.

Setback Requirements for ADUs in Sonoma, CA

In Sonoma, ADUs shall be located subject to the following setbacks, and in conformance with any easements and building envelopes:

  • Front setbacks as established by the base zoning district.
  • Side and rear setbacks should be a minimum of 4 feet.
  • No setback shall be required for an ADU converted from existing space within the primary residence or an accessory structure, or for an ADU constructed in the same location and to the same dimensions as an existing accessory structure.

Maximum Size for ADUs in Sonoma

Maximum Area

  • Detached ADUs: The maximum floor area shall be 1,200 square feet for detached accessory dwelling units.
  • Attached ADUs: An attached accessory dwelling unit is allowed a maximum floor area of 1,200 square feet.
  • Conversion ADUs: The maximum size of an ADU conversion shall be the dimensions of the structure plus an addition of no more than one hundred fifty (150) square feet to accommodate ingress and egress. An expansion greater than one hundred fifty (150) square feet may be permitted up to a maximum unit size of one thousand two hundred (1,200) square feet.

Maximum Height

  •  ADUs shall be limited to the height limit for accessory structures established by base zoning district, except that the maximum allowed height shall not be less than sixteen feet (16′).

Sonoma ADU Rentals

Sonoma County allows ADUs to be used for rental purposes and as a source of passive income, however, accessory dwelling units and junior accessory dwelling units may only be rented in increments of 30 days or more. Neither an ADU nor a JADU can be rented for periods of less than 30 days.


Parking Requirements for ADUs in Vallejo

One (1) parking space is required for accessory dwelling units in Sonoma. The parking space may be located in an existing driveway as tandem parking.

No parking is required if any of the following apply:

  • The property is located on a lot zoned HD (Historic District) Combining Zone
  • The property is within 0.5 miles of a transit stop
  • The ADU is part of the existing or proposed primary residence or within an existing accessory structure
  • When on-street parking permits are required but not offered to the occupant of an ADU
  • The property is within one block of a car-share vehicle.
  • The ADU is a studio unit

For an internal conversion ADU or for a JADU, additional parking is not required. Replacement parking for existing dwelling unit(s) is not required when a garage, carport, or covered parking structure is physically replaced by an ADU.

View All Sonoma ADU Regulations

Custom ADU Builder in Sonoma

Backyard Unlimited has helped our Sonoma County neighbors increase their liveable space and property values by adding accessory dwelling units to their properties.

Over the years, we have worked throughout the greater Sonoma area, installing ADUs and backyard structures in Santa Rosa, Vallejo, Petaluma, and Napa.
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