Burdensome regulations stymie backyard cottage production, UC Berkeley study finds

an image of a well-lit backyard cottage

Building new backyard cottages — called accessory dwelling units — is a critical part of fixing California’s housing crisis, says Karen Chapple, chair of UC Berkeley’s city and regional planning program. (Photo courtesy of UC Berkeley.)

Despite numerous California state legislative wins in support of Accessory Dwelling Units (ADUs) in the last three years, local regulations still limit their production, UC Berkeley researchers have found.

UC Berkeley’s Center for Community Innovation graded local ADU ordinances throughout the state on a scale of A-F on their friendliness to ADU construction. Researchers reviewed over 200 ordinances based on 16 equally weighted criteria assessing their consistency with state law and user-friendliness for homeowners. Cities received extra credit for relaxed parking requirements for ADUs and maximum size requirements for attached and detached ADUs.

“Making it easy to build ADUs is a critical piece of the comprehensive approach to housing needed to solve California’s affordability crisis,” said Karen Chapple, faculty director of the center and professor and chair of the Department of City and Regional Planning. “Delighted as we have been with California’s progress in ADU reform, we were dismayed to see that many cities are writing new ordinances that are still complex and burdensome for homeowners.”

An interactive map , released this week, accompanies a longer report describing the grading process and highlights several ADU best practices.

California ADU ordinances average C+ grade

Researchers found that with some exceptions, California’s jurisdictions are not producing very good ADU ordinances. The average and median grade for local ADU ordinances in California is C+.

Not surprisingly, grades vary across the state. California’s rural region did relatively well, with an average B- score among its jurisdictions. Many larger jurisdictions that have already boosted their ADU production received scores in the A- or B range. A case in point is Los Angeles County, with an A-, which permitted 706 ADUs in 2018, and San Francisco, with an A-, which permitted 364 ADUs.

North-South-Central differences in ADU regulatory limits

Where jurisdictions fall short is in imposing additional layers of review or entitlements, or charging extra fees ranging from impact fees for parks, to fees for utility connections and permitting fees. In general, Northern Californian jurisdictions performed worst in terms of these onerous requirements.

Jurisdictions in Southern California have instituted a number of regulatory limits that may slow ADU production. For example, the Inland Empire stands out for high minimum lot sizes, low height limits, challenging setback regulations and arduous parking requirements. Height limits are also problematic in Los Angeles County jurisdictions, and high minimum lot sizes are a barrier in neighboring Orange County jurisdictions as well. The Central Valley and more rural parts of the state have ordinances that are extremely vague, and others have overly strict setback regulations.

In 2019, the California State Legislature passed a package of ADU bills designed to address some of these regulatory barriers. Effective January 1, 2020, this legislation removes some of the common regulatory tools that localities have employed to limit the potential for ADU construction, such as minimum lot sizes, among other requirements.

San Diego and Sebastopol are bright spots

Researchers found that certain jurisdictions, like the City of San Diego and Sebastopol, have integrated certain features into their ADU programs and ordinances that help create a regulatory environment particularly friendly to ADU construction. These include relaxed parking requirements, permissive zoning and homeowner outreach and financing programs.

UC Berkeley researchers expect that the map will serve as a valuable tool for policymakers and local jurisdictions by highlighting ADU-friendly ordinance best practices. These provide important examples as cities must revise their ordinances again in the coming years to comply with new state laws. The map and website will be updated on an ongoing basis to showcase promising practices, rewarding jurisdictions who improve their ordinances with a higher grade.