With a pen stroke, Gov. Gavin Newsom has set the stage for potentially massive changes to how housing is built in Silicon Valley.

Newsom signed into law Senate Bills 9 and 10 on Thursday. SB 9 allows for the development of up to four dwelling units on single-family lots throughout California, while SB 10 allows local governments to streamline multi-family housing projects of up to 10 units near transit and urban cores.

Proponents of the legislation are thrilled by the prospect of being able to build more densely in San Jose, which they say will create more affordable housing and undo the legacy of racial segregation caused by single-family zoning.

“We’re extremely excited,” said Cory Wolbach, community engagement senior associate with SV@Home and the group’s Action Fund, which supported both bills. “If multiple homes can share the same plot of land, each home will be less expensive… it doesn’t mean it will be cheap, but it’s an incremental step toward affordability.”

Long-term implications

The cost of living is a growing concern in San Jose, where home prices remain out of reach for many residents. City leaders are considering a proposal similar to the state bills called Opportunity Housing that would allow up to four units on lots currently zoned for single-family homes.

The San Jose City Council is expected to consider exploring Opportunity Housing next month, but it’s unclear how officials will factor in the state’s latest rules.

“SB 9 is important legislation intended to facilitate the development of much-needed housing throughout our state,” Jeff Scott, spokesperson for the city housing department, told San José Spotlight. “We are currently reviewing the legislation to fully understand it’s long-term implications for the housing stock in San Jose.”

Wolbach said it’s hard to tell how much housing the state bills will produce in San Jose and the surrounding area. He stressed that cities and local communities will have to figure out how to put these bills to best use.

“The details of implementation are really up to the city,” Wolbach told San José Spotlight. “It leaves a lot of room for cities throughout Santa Clara County to figure out what works best for them, acknowledging the era of exclusionary, one unit per parcel zoning is moving toward the rearview mirror, finally.”

A doorway to unpredictable development?

Opponents of the two bills claim they will lead to rampant and unpredictable development in San Jose’s residential neighborhoods.

“For anyone who owns a home, the lot next door to them could change,” said Planning Commissioner Pierluigi Oliverio. “You don’t know if that’s going to be next week, next month, or next year, but that potential is going to change the street they bought on.”

He told San José Spotlight there will be a host of other issues as previously zoned single-family neighborhoods have to deal with the influx of development: loss of parking, loss of tree canopy, loss of privacy, added noise and strains on utilities that weren’t designed for multiple families living on the same lot.

“San Jose has never been one to not build housing — we’ve always done it, and we’ve got to plan to build a ton more housing in a smart manner,” Oliverio said, noting that San Jose’s current general plan projects growing the population by 40 percent by 2040.

Doubling down on high-density housing near transit would maximize the creation of affordable units and be better for the environment, he said. But the state laws disrupt that, which he claims is a massive mistake.

“This, unfortunately, will forever hurt the good will of everyday residents who will no longer trust government when it comes to land use,” Oliverio said.

Voters may get their say

There’s a chance the laws will be yanked in the 2022 election. A group called Californians for Community Planning is working to put a measure on next year’s ballot that would amend the state constitution to make zoning and land-use local affairs.

Ilya Gurin, a Mountain View resident and member of South Bay YIMBY, said the state laws are overhyped.

“In many cases, it won’t actually be economically feasible or justified to redevelop existing houses,” Gurin told San José Spotlight.

Instead of residential neighborhoods seeing the mass creation of fourplexes, Gurin anticipates most redevelopment will consist of homeowners creating duplexes or accessory dwelling units to accommodate multi-generational families.

He also said the creation of more housing will help reduce economic segregation in the South Bay.

“Desegregating housing and mixing up neighborhoods is very important to create opportunity for people who need it,” he said.

Contact Eli Wolfe at eli@sanjosespotlight.com or @EliWolfe4 on Twitter.

This story originally appeared in San Jose Spotlight.