Accessory Dwelling Units

Accessory Dwelling Unit Types:

• Detached ADU shall mean an ADU that is constructed either to expand the footprint of the existing single-family residence or accessory structure, or to be a new accessory structure on the parcel.

• Attached ADU shall mean an Accessory Dwelling Unit that is constructed and contained within the existing space of the single-family residence or accessory structure and has an independent exterior access from the existing residence.

• Junior ADU shall mean an Attached Accessory Dwelling Unit that does not exceed 500 square feet, includes an efficiency kitchen, and may either share a bathroom (toilet, sink, and tub and/or shower) with the principal residence or have its own bathroom. The principal residence or the JADU must be occupied by the owner of the residence.

Capacity Charges:

Capacity charges are required for detached ADU that are 500 square feet or larger. Capacity charges are not required for attached ADU or junior ADU. For capacity charges for detached ADU, refer to NapaSan Code Section 5.02.030. Section 5 of NapaSan Code can be found here. Payment of capacity charges is required prior to issuance of a building permit.

Development Fees:

Development fees are required for ADU and include plan check fees and inspection fees. Development fee information can be found here

Plan Submittal:

Submit a set of plans directly to Napa Sanitation District at the Administrative Office located at 1515 Soscol Ferry Road.

Sewer Service Charges:

Additional sewer service charges (assessed annually) apply to parcels with ADU. Sewer service charge information can be found here.