This California law was supposed to end single-family zoning. Three years later, it’s ‘just symbolic’

By Christian Leonard, Data Reporter Feb 21, 2025
https://www.sfchronicle.com/realestate/article/california-sb9-housing-duplexes-20175585.php

California Senate Bill 9 aimed to allow homeowners to more easily create duplexes, like this one in Oakland. But three years later, few have been built. Gabrielle Lurie/The Chronicle

When it went into effect in 2022, Senate Bill 9 was hailed as one of the biggest — and most controversial — housing laws in years. Observers called it the end of single-family zoning in California, with the law essentially legalizing duplexes in large swaths of the state’s suburbs. Combined with its lot split provision, SB9 let homeowners turn one home into as many as four.

But three years later, California’s suburbs largely look the same as they did before SB9 — prompting legislators, including state Sen. Scott Wiener, to take a swing at tweaking it.

San Francisco has received just 32 construction applications under SB9. San Jose has gotten 37, and Oakland has received only five. For comparison, San Francisco received more than 460 applications for accessory dwelling units, aka ADUs, in 2022 and 2023 alone, according to data from the state department of Housing and Community Development.

Those cities are among those where SB9 projects are most financially viable, according to a 2023 analysis from the UC Berkeley Terner Center for Housing Innovation. The study, based on a small sample of California cities, said at the time that SB 9’s impact was “limited.” Things haven’t changed much since then, experts say.

“This is just symbolic at this point,” Chris Elmendorf, a property law professor at UC Davis, recalled thinking of SB9 when it was signed. “This isn’t going to do anything, or it’s going to do very little.”

Applications submitted for SB 9 projects, by type of application

Among selected Bay Area cities, 2022-24

A table showing that for every city, the number of construction applications was less than 40, and the number of lot splits was less than 45.

Data includes withdrawn applications. Oakland’s data do not include figures for 2024.
Table: Christian Leonard / The Chronicle Source: Planning departments

The UC Berkeley Terner Center for Housing Innovation estimated in 2021 that SB9 would make roughly 700,000 new homes financially worth building. David Garcia, who co-authored the report, said that was a conservative estimate — one SB9 has come nowhere near.

Wiener, whose district includes San Francisco, launched a major attempt at strengthening SB9 this week, introducing a bill that would address some of the most common issues housing researchers have raised with the law. SB677, introduced Friday morning, would prohibit cities from requiring homeowners to live on the property for at least three years after they get approval for a lot split — a restriction some housing advocates said is SB9’s greatest flaw. It would also prevent homeowners associations, which experts say have effectively banned SB9 projects in many parts of California, from restricting such proposals in their neighborhoods. SB677 would also make Wiener’s landmark housing streamlining law, SB423, stricter on cities.

“SB9 was a huge, huge step for the state of California,” Wiener said. “And now we want to make the law as good as it can be.”

One of the selling points of SB9 was that it would be fast. It requires cities to approve duplexes and lot splits in single-family neighborhoods ministerially, meaning they aren’t subject to the often-lengthy hearings that delay other housing projects.

But there were problems from the start, researchers said. The law requires lots to be split roughly in half, but since many homes are located in the middle of the property, meeting that requirement would mean cutting the house in half. The owner-occupancy requirement, which property law professor Elmendorf called a “poison pill,” was designed to keep investors from flipping lots. But the high costs and complexity of the SB9 process often make it more trouble than it’s worth, especially as many cities added extra restrictions on duplexes after the law’s passage.

“If you don’t know what you’re getting into, it becomes your full-time job,” said Gloria Riechers, who co-owns Riechers Engineering, an engineering firm that specializes in SB9 lot splits.

SB450, by then-state Sen. Toni Atkins, who authored SB9, strengthened the law in 2024. Among other things, it requires cities to respond to SB9 applications within 60 days and restricts their ability to set special limits on proposed duplexes.

Garcia, the Terner Center researcher, called SB450 “a step in the right direction.” But he added more reforms are needed before SB9 projects have a chance of taking off.
“Just because a (project) works on paper, doesn’t mean it works in practice,” Garcia said. “And we’re kind of seeing that now.”
Even if Wiener’s SB677 passes, it’s unclear how many more projects would start. Some homeowners are simply uninterested in adding another unit to their property, and those who are have other, often faster options — most notably ADUs.

But ADUs may themselves point the way to eventually making SB9 successful, housing experts said. After all, the first California law promoting ADUs wasn’t passed until 1982, where it sat largely unused for decades, Elmendorf said. It’s taken about a decade of legislation for ADUs to become a reliable source of new housing, explained Noerena Limon, CEO of housing advocacy organization the Casita Coalition. It may very well take years for SB9 to bear similar fruit.

“If you don’t remove all the barriers, you don’t get (homes built),” Limon said.

Reach Christian Leonard: Christian.Leonard@sfchronicle.com
Christian Leonard is a data reporter for the San Francisco Chronicle. He joined the Chronicle in 2022 as a Hearst Developer Fellow. He previously worked as a senior staff writer at the Outlook News Group, a collection of community newspapers in Los Angeles County. He is a graduate of Biola University, from which he received a bachelor’s degree in journalism and integrated media, and interned at NBC Los Angeles.