Sometimes called granny flats, in-law units, second units, casitas, or backyard cottages, Accessory Dwelling Units (ADUs) share several distinguishing features: they are 250 to 1,200 square feet and must have a kitchen or kitchenette, bathroom and sleeping area.
ADUs are, by nature, affordable, helping seniors age in place, creating affordable rental units quickly, and benefitting homeowners who need additional income to make ends meet.

The state of California identified ADUs as a promising solution to our growing housing crisis and, over the last three years, the State has been updating laws to make it easier and less expensive for homeowners to build ADUs—all leading to an increase in the number being built.

Locally, after the 2017 fire, the city of Santa Rosa’s planning department moved quickly to reduce permitting fees, making it easier for people to build ADUs and leading to a dramatic increase in ADU development. In just four years, the number of homeowners building ADUs in Santa Rosa jumped from 7 per year to 197, with 80 added on to plans for properties destroyed in the fire.

Growth of ADU's in Santa Rosa

All nine Sonoma County cities agree that accessory dwelling units are an excellent supply-side solution to our housing crisis. Still, the mix of local regulations has been confusing to many homeowners looking to build an ADU—something local planners would like to change.

To help solve this, we partnered with Napa Valley Community Foundation (NVCF) to encourage a regional approach to ADU development. We started by convening local planning departments to help foster cross-collaboration and find areas where planners could learn from one another. We also worked to create new, easy to navigate tools for homeowners who wanted to learn more about building an ADU on their property.

The website was the first step—offering a one-stop portal for homeowners to look up local regulations, view floor plans, and estimate costs.

In 2020, we are excited to announce that our partnership with NVCF will grow, with the opening of the ADU Napa Sonoma Center, which will offer both virtual and in-person services to help homeowners design, build, and lease ADUs throughout Napa and Sonoma Counties.

screenshots of website

To learn more about building an ADU, visit

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