Accessory Dwelling Units (ADUs)
ADUs are an inexpensive way to create smaller, more affordable rental housing units that may provide revenue streams for you, while increasing the availability of rental housing in the county.
Accessory Dwelling Units (ADUs) are known by many names like granny units, in-law units, second units, and backyard cottages. An ADU is a small dwelling unit that may be established in addition to single-family or multifamily dwellings in residential, mixed-use, or agricultural zones. An ADU may be detached, attached to the primary dwelling or other accessory structure, or located within a main dwelling and may involve new construction or conversion of an existing structure (such as a detached garage or other accessory structure, or a portion of a dwelling).
Changes in State law related to accessory dwelling units took effect January 1, 2020
The Building Division is responsible for managing the construction permitting process. This process includes general public information, plan submittal, plan review, permit issuance, inspection and document retention. The Building Division is also charged with the task of assuring that all additional approvals required by both inside and outside entities are obtained prior to the issuance of both a building permit and receiving final inspection approval.
The following is provided to help you understand and navigate Napa County’s building permit process. A process flowchart (PDF) is available for your review and use. The flowchart illustrates the involvement of other County Departments, and state and local agencies that may assist us in our review process depending on scope of your project. If you need assistance or need clarification regarding the permitting process, please feel free to contact us.
Once you have prepared all required documents, you must submit those documents at the Building and Development Division counter. At the time of submittal, you should be prepared to provide the following:
- Location of the project (street number and name) and Assessor’s Parcel Number (APN)
- Legal owner’s name, mailing address and daytime telephone number
- Contractor’s name, license number, Workman’s Compensation policy number
- Description/Narrative of your project
- Cost of all the proposed work - (labor and materials)
- Soils Report (if required),
- Payment of any required submittal fees
Note: The property owner, an authorized (i.e., in writing) agent, or licensed contractors are the only individuals who can legally sign the application and submit for the building permit.
For building a new residence, a submittal checklist (PDF) is available to assist you in determining what kinds of documentation will be required. If you are altering an existing residential structure, we have a submittal checklist (PDF) to help you too. Commercial projects have their own unique requirements. Please consult the commercial construction checklist (PDF) prior to submitting your plans.
Building Permit Applications
Quick Permits is an accelerated building permit process for minor projects that qualify as "Quick Permits." Not all permit types qualify. The types of projects that would qualify would be agricultural buildings, carports, decks, garages, gazebos, retaining walls and other various small projects. Each scope of work is subject to review and may or may not qualify. All completed applications for the Quick Permit program will be plan reviewed and you will receive comments on the plans within 7 to 10 business days. See if your project qualifies by reviewing the Quick Permit Overview (PDF).
The Building and Development Division offers over-the-counter permits, which can be issued same day during regular business hours. Over-the-counter permits include the following permit types:
- Water Heater (tank-less not included)
- Minor Electrical and Plumbing
- Furnace Change-out
- Electrical service upgrades
- Agricultural electrical service
The Division also offers a same-day review for smaller projects. Same-Day Permit review is Monday through Thursday, from 8 to 10 a.m. only. Depending on the volume of traffic, expect to spend one to two hours at the Permit Center having your project reviewed. Before coming in to the office check to see if your project qualifies as a Same-Day Permit.