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

With recent updates to California’s ADU laws, Napa 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 Napa’s special use regulations for accessory dwelling units.


Napa ADU Zoning Requirements

Zoning Regulations:

  • The lot for a proposed ADU must be zoned for single-family use and must contain an existing single-family residence.
  • Only one ADU/JADU is allowed per lot.
  • Not allowed on lots zoned for duplex or multi-family lots.

Setback Requirements for ADUs in Napa

  • Detached ADU Setbacks: The ADU is required to provide a minimum setback of 3 feet from the property line and the primary residence.
  • Attached ADU Setbacks: The ADU shall follow the required setbacks for the zoning district in which is it located.
  • Conversion ADU Setbacks: Setbacks must be sufficient for fire safety to prevent the spread of fire.

Maximum Size

Maximum Area:

  • A new ADU is limited to a floor area not to exceed 50% of the floor area of the primary residence up to a maximum of 1200 square feet.

Maximum Height:

  • The Accessory Dwelling Unit shall comply with the height requirements for the applicable zoning district.
  • The ADU shall be limited to 15’. Building heights greater than 15’, without going over maximum height for the zoning district in which the ADU is located,  may be granted with the approval of an administrative permit.

Napa ADU Facility and Utility Requirements

Facility Requirements: An ADU shall provide a separate bathroom and a separate kitchen from the primary residence.

Utility Requirements: New or separate utility connections may be required, but connection fees or capacity charges shall be proportional to the impact of the ADU on the sewer or water systems. Contact the following entities for additional information related to utility connections:

  • Water – City of Napa Utilities Department: (707) 257-9521
  • Sewer – Napa Sanitation District: (707) 258-6000
  • Gas and Electricity – PG & E: 9707) 257-5918

Parking Requirements for ADUs in Napa

One (1) parking space per bedroom is required to be provided on-site.

No additional parking is required if:

  • The property is located in a historic preservation district
  • The property is within 0.5 miles of a transit stop
  • 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.

For an internal conversion ADU or for a JADU, additional parking is not required.

View All Napa ADU Regulations

Custom ADU Builder in Napa

Backyard Unlimited has helped our Napa 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 Napa Valley area, installing ADUs and backyard structures in Vallejo, Petaluma, Santa Rosa, and Sonoma.
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