Permits have shot up after California passed a landmark law in 2016 to make it easier to permit and construct accessory dwelling units (ADUs).
The Terner Center for Housing Innovation at UC Berkeley has released a new brief [pdf] that "discusses the benefits of ADUs for supply-restricted and cost-burdened regions, and examines data from California’s largest cities (and a handful of other jurisdictions) to measure how much interest in, and production of ADUs has increased in the past year."
"The results are telling: across the board cities are seeing significant increases in ADU applications, with many cities doubling, tripling, or even quadrupling their totals from 2016," according to a post announcing the new report. For instance, Los Angeles saw 90 ADU applications in 2015. In 2017, that total reached 1,980.
The policy brief includes recommendations for removing some of the remaining barriers to ADU permitting and construction in cities around the state.
Read the full story: ADU UPDATE: EARLY LESSONS AND IMPACTS OF CALIFORNIA’S STATE AND LOCAL POLICY CHANGES
ADUs account for nearly 28% of Bay Area housing permits
In Hillsborough, 56 of 58 homes permitted in 2025 were ADUs.
Report: Massachusetts zoning reform not enough to stimulate ADU production
Massachusetts cities issued over 1,200 applications for ADUs in the last year, short of the Healey administration's goal of 1,600 to 2,000 units per year.
ADUs accounted for 9% of new Maine building permits in 2025
Maine officials approved roughly 500 ADU permits last year.
Planetizen Federal Action Tracker
A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.
California plans to bury El Niño’s downpour
If the state plays its cards right, it may be able to store a billion acre-feet of El Niño’s water in aquifers.
Desperate measures: Advocates weigh draining Lake Powell to fill Colorado River
Draining the reservoir could reduce evaporation losses by a couple hundred thousand acre-feet.
How a Chicago-sized wind farm beat the odds and powered on
The project spanned five presidential administrations and a standoff with a U.S. military base.
MTA gives itself 30 days to transform pit into basketball court
The site has been under construction since 2022; the city originally estimated it would finish the court in 2024.
Non-stop party: Chicago voters weigh permanent festival grounds
A stable place for bleachers, stages and drainage may streamline the setup and teardown of large events.
FREE Course: Walkable City 1: Why Walkability?
After describing his path towards focusing on walkability as the essence of good planning, Jeff Speck marches through his five principal reasons for making more walkable places.
Reinventing Malls: Planning Alchemy—Turning Gray Fields Into Gold
The course focuses on the opportunities and imperatives that shape reinvention of mall sites.
City of Rosemead
Rutgers University, Edward J. Bloustein School of Planning and Public Policy
One Hundred Miles
Hunter College, City University of New York (CUNY)
The Architects Foundation
University of Cincinnati Online
City of Cambridge
Montrose County
The Pocatello Development Authority