County of Napa - Napa Sonoma ADU Center

Thinking about an ADU? Schedule your personal consultation

Home > Local Rules > County of Napa

Local ADU Rules

County of Napa

Last Updated August 26, 2024

ADU Contact:

Affordable ADU Program, Forgivable ADU Loans: https://www.countyofnapa.org/3424/Affordable-ADU-Program-Forgivable-Loan-O
Trevor Hawkes, trevor.hawkes@countyofnapa.org
Jennifer Palmer, jenifer.palmer@napacounty.org

Standards	Details
Zones allowed	All residential districts, AW – Agricultural Watershed Only JADUs allowed in AP – Agricultural Preserve Farmworker units allowed in all residential and agricultural districts
Lot Restrictions
Minimum Lot Size	Legal lot of record (there is no minimum lot size requirement to construct an ADU)
Min/Max ADU Size	No Minimum Maximum of 1,200 square feet Maximum 500 square feet for JADU
ADU Building Height	16 feet, or up to the height limit of the underlying zoning with approval of an administrative permit.
Setbacks	Detached: 4 feet side and rear, front setback is the same as the underlying zoning. Attached: the same as the underlying zoning.
Parking Requirements	Each ADU shall have one parking space. parking requirements shall be waived if the ADU is located: within one-half (1/2) mile walking distance of a public transit stop; in a designated historic district; in part of a principal dwelling unit or an existing accessory structure; in an area requiring on-street parking permits but the permits are not offered to the ADU occupant; or within one block of a car-sharing pickup/drop-off location.
Owner Occupancy	For JADUs, the property owner shall reside in either the principal dwelling unit or the JADU.
Sample fees from recent permits	Chart of sample ADU fees available on the Napa County ADU webpage: https://www.countyofnapa.org/2750/Accessory-Dwelling-Units-ADUs Entitlement: No Building: Fee based on project valuation Impact Fees: School Water: Most projects on private well Sewer: Most projects on private septic School: Napa, St. Helena *Fees are specific to each project and will vary. Fees change regularly. These are provided as examples only.
Other requirements	Deed restriction – cannot be sold separately Water and sewage requirements
Process	Approved through building permit. Disclaimer: standards and process may vary. Consultation with the contact is recommended before starting any project.
Exceptions	Road and access requirements approved by engineering and fire Appeal to Board of Supervisors

Wondering what you can build?

Make sure you check out our Learning the Rules page for more step-by-step details