Published: July 10, 2019
The County of Sonoma is partnering with local cities and the County of Napa to develop a regional
Accessory Dwelling Unit Calculator to encourage our constituents to build accessory dwelling units (ADUs). This online tool helps individuals estimate the costs, returns, and benefits associated with building an ADU.
The Sonoma/Napa calculator is based on San Mateo County's Second Unit Calculator, and was developed by Baird + Driskell Community Planning with funding from ABAG/MTC, the California Department of Housing and Community Development, Community Foundation Sonoma County, and Napa Valley Community Foundation.
Find out more about Accessory Dwelling Units and whether your property meets the requirements to add a new ADU. If your property does meet the requirements for an ADU, enter your specific information into
the calculator to get an estimate of what it would cost.
Try the Sonoma/Napa Accessory Dwelling Unit Calculator (Note: Calculator works in Firefox and Chrome)