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Sonoma County Updated Accessory Dwelling Unit Ordinance

The trend of ADU development doesn’t appear to be slowing anytime soon with the number of Sonoma County ADU applications increasing significantly from 2016 to 2020. Over 600 ADU applications were applied for and 200 were issued. In 2020, 1 in 3 housing units permitted were ADUs. A pace that will help meet the area’s projected housing needs over the coming decade. The recent update to the Regional Housing Need Allocation (RHNA) set housing goals for Sonoma County 3,881 new homes in rural Sonoma alone. 

Although ADU development in the County is growing, it’s uneven with Santa Rosa having the fewest ADU applications and District 1 (southeast Sonoma County) having the most applications.  The updates couldn’t come soon enough with Sonoma County’s District 1 population projected to increase by nearly 100,000 in the next two years. To meet the demand of workforce housing alone Sonoma County will need nearly 60,000 additional homes, many of which will need to fall into the affordable category given the area’s median income

Seaside California ADU 1 Bedroom

To comply with state law, and meet the growing demand for affordable housing, Sonoma County is updating the County Accessory Dwelling Unit Ordinance. Staff recently recommended that the Board of Supervisors adopt the proposed ordinance at the September 14, 2021 Board of Supervisors meeting. Although the County has been implementing state law since its passage in 2020, the adoption of the ordinance will allow for County staff to further help homeowners building ADUs. The goal of the ordinance update was to bring the County ordinance into compliance with state law. 

Sonoma County planning staff Katrina Braehmer presented the updates to the Board at the September meeting. Changes to the zoning code include the removal of the prohibition of ADUs on contracted land, although ADUs are not allowed on properties subject to the Williamson Act which limits activities to farming in exchange for a reduced tax liability. Conversions of legally established spaces need not comply with side and rear setbacks although new construction is subject to front yard setbacks. ADUs are also now allowed for multifamily structures so long as they meet state standards.

The bureaucratic process is streamlined as well; ADU projects will no longer require zoning or use permits to help streamline the process and approve projects within the 60 day timeline. The most significant change is the removal of the minimum lot size requirements and discretionary review but applicants must still prove adequate water and sanitation for the proposed home. 

The ordinance update was funded by a Housing and Urban Development early action planning grant. In addition to the ordinance update, the grant will also fund a number of Sonoma County projects including the establishment of objective design standards. No public comments were submitted during the public hearing for the ordinance amendment, the Board of Supervisors unanimously adopted the update. The State is also providing some economic incentives in the form of loans for ADU construction and grants of up to $25,000 to make living in Sonoma County more accessible.