An analysis by the Bay Area Council Economic Institute using data from the California Department of Housing and Community Development (HCD) shows Accessory Dwelling Units (ADUs) accounted for 13.4 percent of all housing permit types in the Bay Area in 2020, a significant jump from 3.2 percent in 2016. In Marin and Napa, the Bay Area counties permitting the lowest amount of housing, ADUs are the majority of permits, making up 49.4 percent of all housing permits in Marin County and 40.3 percent in Napa County.
Since the Bay Area Council partnered with Senator Bob Wieckowski to pass the first significant Accessory Dwelling Unit (ADU) reform legislation in 2016 (SB 1069), ADU permits have soared across the state. With other housing permits remaining stagnant or falling, ADUs represent a bright spot in California’s housing crisis. The Council continues to advocate for reforms to expand access to ADUs, including most recently sponsoring legislation by Assemblymember Phil Ting (AB 561) making it easier for homeowners to finance ADU construction. For questions or to engage in the Council’s housing policy work, please contact Senior Policy Manager, Kelli Fallon. For questions on this data visualization, please contact Research Manager, Abby Raisz.