Accessory Dwelling Units (ADUs)

"Accessory dwelling unit" or "ADU" means an attached or a detached residential dwelling unit, which provides complete independent living facilities for one or more persons. An ADU shall not have direct access to the primary residence. It shall include permanent provisions for living, sleeping, eating, cooking, and sanitation on the same parcel the primary dwelling unit is situated. An accessory dwelling unit also includes the following:

     1. An efficiency unit, as defined in Section 17958.1 of the Health and Safety Code; and

     2. A manufactured home, as defined in Section 18007 of the Health and Safety Code.

"Junior accessory dwelling unit" or "JADU" means a residential dwelling unit that is no more than 500 square feet in size and contained entirely within an existing single-family structure. A junior accessory dwelling unit may include separate sanitation facilities, or may share sanitation facilities with the primary dwelling unit and have direct access to the primary dwelling unit. Junior accessory dwelling units are limited to one per residential lot zoned for single-family residences with a single-family residence built, or proposed to be built, on the lot.

Interested in building an ADU? 

ADU Image

Review the following resources to learn more:

The Napa Sonoma ADU Center Standard Plans Program

The Town of Yountville is excited to partner with The Napa Sonoma ADU Center and other jurisdictions around Napa and Sonoma counties to support residents in planning for and building ADUs. The Napa Sonoma ADU Standard Plans Program provides property owners with easy access to dozens of "off the shelf" ADU plans that can be purchased at low cost, saving thousands of dollars and months of time over a custom design. Plan options include site-built and prefabricated designs of various sizes, including "pre-reviewed" plans.

Pre-Reviewed Plans

Pre-reviewed plans include prefabricated ADUs that have already been reviewed by state or federal code reviewers as well as site-built ADU plans that have been reviewed by a third-party reviewer, BPR Consulting Group, for compliance with applicable building codes. Visit the program's FAQs page for more information.

Pre-Reviewed ADU Plans in the Town of Yountville

Town staff has not reviewed any of the plans for code compliance. We will accept plans that have been reviewed and approved by BPR (or other approved third-party plan review) and will formally review them upon submittal.

Remember that even pre-reviewed plans must be submitted along with a formal application and additional information to receive a building permit. 

Why Use a Pre-Reviewed Plan

Because these plans have been developed to be code compliant, it saves the homeowner time and money in developing useable plans. The project will still need to be reviewed and approved by the Building Department for location on the lot, utility connections, fire setbacks and fire sprinklers (if required), as well as Planning Department and Public Works approval. The typical plan review for most projects is 28 days. 

First Steps

Regardless of whether you choose a pre-reviewed plan, another standard plan, or develop a custom plan, it is essential that you determine in advance the size of ADU you can build on your property and other factors that might limit or define necessary features of your ADU. You can do this by contacting The Napa Sonoma ADU Center and/or by making an appointment with our Planning and Building Department.

You are welcome to call the Planning and Building Department to speak to a planner about your ADU project. You can reach us at 707-944-8851.