• Napa Valley Marketplace Magazine

Accessory Dwelling Unit - Building Solutions, One Home at a Time

By Linda Bausch



The availability of new or existing homes on the market locally, for sale or rent, has been at a disadvantage for many years. In the Valley, when homes do go on the market, the prices are exorbitant and out of reach for many, while available land for creating new, affordable living opportunities is also negligible. This situation has more recently been negatively impacted by other major events, unforeseen and tragic. Of course, I am talking about the recent scourge of wildfires (again). In my research for this article, I was reminded of the many thousands of homes and other buildings that were destroyed, the results compounding an already drastic situation. Thankfully some rebuilding has taken place but nowhere near what we need to flesh out the local housing needs, prior to or since.


This is of great concern for many; young residents who have grown-up and are ready to move on from the family home being priced out before the can make a phone query to qualify for a loan; the hospitality employee or farmworker who lives thirty miles away and would like to reduce the commute; an elderly relative needs a bit more support, and is well enough to be in their own space, but can’t afford the options currently available, or they just want to be close to someone who cares.

Let’s focus on positive housing solutions being made in small, impactful ways, one dwelling at a time.


A California law passed in 2020 required cities to relax approvals and regulations imposed on such construction known as Accessory Dwelling Units (ADUs). An ADU is generally known as Granny or In-Law Unit. They are situated in backyards or on properties of pre-existing homes. Some may even be additions.

There are some restrictions to this type of build—an example—Unincorporated County—the Ag Preserve is a no-go as far as this option goes; if water restrictions are in effect in a certain area, or a property operates on a septic-system, unless you can accommodate the additional usage with your existing system, or you are able to afford an upgrade, building an ADU will not be allowed. That still leaves many other homes in the running to be considered for an ADU permit. (There may be exceptions for allowing Junior ADUs within the Ag Preserve and water deficient zones.) Permits are required by law to be processed within a sixty-day time frame.

There are many variables to such projects and planning is of the utmost importance.

On the Napa Sonoma ADU Center website [NapaSonomADU.org] you will find tools and resources to support local homeowners with building ADUs, an on-demand ADU webinar library, as well as, an Upcoming ADU Webinars Calendar.


Some Key ADU topics you will find helpful:


Garage Conversion ADUs

Napa Sonoma ADU developed a helpful handout on garage conversions in partnership with the Casita Coalition and others—plus a very helpful webinar is recorded.


Cost of ADUs

Check out their ADU Calculator—which will walk you through the cost and also the return on your investment over time. They also recommend you check out the ADU Workbook for the chapter on Budgeting & Finance, starting on page 33.


Financing ADUs

Watch their on-demand webinar, How to Finance Your ADU (for Napa & Sonoma County Homeowners), as well as, their recent webinar with Redwood Credit Union on their NEW ADU construction loan. Plus, see CalHFA’s new $40K predevelopment grant for ADUs. And look up the local finance experts available on our Vendor Registry. In addition, check out the comprehensive overview of ADU financing from the state-wide Casita Coalition.

Property Value Implications of ADUs

Your ADU will likely add to your home’s value, though the exact amount is difficult to predict because there are few comparable homes to give definitive rules. A very rough rule of thumb is that your new construction ADU will add 100 times the monthly rental value to your home.


Junior ADUs

JADUs will impact the assessed value less than a traditional ADU (or potentially not at all). Since JADUs are a relatively new form of housing, there is currently little data on them.


Taxes and ADUs

To learn more about how an ADU will impact your taxes, read their blog post on the subject. For more individualized or detailed information about your ADU project and taxes, they recommend that you reach out to your local tax assessor and/or a tax professional. Contact information for your county assessor’s office is in the blog post.


Purchasing New Property

Maximizing ADU build potential. See their blog posts on the website.


Also available is a Vendor Registry where reputable contractors/designers may be found. In June, a Napa/Sonoma Standard Plans Program will have a soft launch on the website.


Napa Sonoma ADU Center suggests working with contractors who are reasonably priced for our region and the current market, which means they’ll be honest and up-front with you about the real costs they are seeing in real time for materials and set a contract with you that is realistic regarding fluctuations occurring in the market over time.


Renee Schomp Shared A Few Comments From Satisfied Homeowners:

“[Napa Sonoma ADU Center] provider references, from designer to builders, are solid gold! I don’t think I would even have gotten started without it.”


“The report [from Napa Sonoma ADU] is very helpful. If anything, the biggest thing for us was identifying a space. We didn’t realize feasibility was over the garage and seeing the numbers broken down was great.”

“We received some very valuable feedback [from Napa Sonoma ADU] and we DEFINITELY intend to proceed.”


“Real, local people who really do answer your questions!”

From Carl Strauss: (pre-Jan 2020, did not receive Napa Sonoma ADU help but rather informed the plans for our pilot program). “Chasing warmer weather and better wine, Carl moved to Yountville. He is a walker and a local shopper and over time began making friends with the restaurant owners and staff near his home. But he noticed a problem, every year too many people moved away. People who worked at the stores, no matter how hard they tried, could not afford to live nearby. But Carl had a solution. He built an ADU not only for additional income, but specifically to support employees at nearby Yountville restaurants, from sous chefs to bussers. And it worked! Within weeks of completing his unit it was rented. It’s small, 300 square feet, but has everything someone needs. It is also beautiful with cathedral ceilings and a little patio. The ADU fits in well with his yard, and matches the design of the main house. Best of all, it is a 5-minute commute by foot through the beautiful streets of Yountville to the businesses Carl loves the most.”


In Conclusion:

With much appreciated assistance from Julia DeNatale, Vice President of Community Impact with Napa Valley Community Foundation and Renee Schomp, Director, Napa Sonoma ADU Center, I have been able to compile some information for our readers. (Napa Sonoma ADU Center is a nonprofit fiscally-sponsored project of Napa Valley Community Foundation, with support from Community Foundation Sonoma County and some of our local jurisdictions.)

Whether you are a Do-It-Yourselfer or looking for the ‘perfect’ contractor fit, the information on this subject is mountainous. Developing an ADU involves three basic steps: 1) Design your project; 2) Submit and obtain a building permit; and 3) Build your project. Learn more about the development process here: Your Pathway to a Completed ADU and Building Plan Review Process web page.


An ADU is... generally known as “Granny or In-Law Unit” They are situated in the backyards or on properties of pre-existing homes.


For More Information NapaSonomAADU.org | CityofNapa.org | CountyofNapa.org

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