In an effort to boost the availability of affordable housing in one of the world’s most expensive cities, San Francisco this week joined the growing list of American cities scaling back or eliminating single-family zoning rules that have been a cornerstone of urban planning for decades. 

The Golden City passed legislation Wednesday that ends single-family zoning.  Before the legislation passed, approximately 40 percent of the city’s land area was zoned for single-family houses, meaning only one family could live on each parcel of land.

In a six-to-four vote, the Board of Supervisors approved legislation that will allow all homes currently zoned for single-family residences to become fourplexes. Corner units will now be able to house up to six families.

The median rent for a one-bedroom apartment in San Francisco — the second most expensive real estate market in the country after New York City — is now $2,900 a month, and the overall median rent stands at $3,000 a month, an 11.1 percent increase from last year. The cost of a home there has increased 12.3 percent since this time last year.

The change in zoning laws is intended to reduce restrictions on development, incentivize the construction of denser housing, and increase the overall housing supply in San Francisco.

The move is the latest in a wave of legislative efforts sweeping across the country as states and cities try to bring down the cost of housing, which S&P Global estimates has increased 20 percent in the last 12 months.

Oregon passed a similar law that allows for the conversion of single-family homes into dwellings with as many as four apartments, and New York is considering a law that would limit the ability of  municipalities to impose certain zoning requirements.

Minneapolis recently passed a law that rezoned single-family housing areas to accommodate up to four families per building, though it has yet to be enacted due to procedural hiccups.

In Atlanta, the neighborhood of Buckhead is pushing to secede from the city and form its own municipality. Maintaining its single-family zoning rules has been cited as a key reason for the effort.

The push to rezone is not only happening in large cities. In Montana, a libertarian think tank, the Frontier institute, has proposed a plan to revamp the state’s zoning laws in the name of economic opportunity, fiscal responsibility, and relief from bureaucracy. 

Some, however, are worried that rezoning neighborhoods won’t be enough to incentivize development, a sentiment shared by the San Francisco Planning Commission president, Rich Hillis.

“I’m just nervous that the changes they’re making are either not going far enough, or they’re putting requirements in place that will result in too few units being produced,” he told the San Francisco Chronicle.

A senior research fellow of Harvard’s Joint Center for Housing Studies, Alexander von Hoffman, agrees, writing that “it will take more than simply removing single-family zoning to increase the supply of housing enough to bring prices down.

“To unleash residential development will require peeling back layers of regulations that have accrued over the decades,” Mr. von Hoffman said.

Among the measures Mr. von Hoffman has proposed are reducing minimum lot sizes, relaxing strict construction laws, and rolling back “some” environmental standards.

Even President Obama appears to be on board with the efforts, arguing that “some very well-intentioned laws and regulations at the local level — often generated from the left and from my own party — sometimes are inhibiting the creation of affordable housing.”

According to a professor of planning and law at Cornell University, Sara Bronin, the push for zoning changes are a necessary first step in incentivizing new affordable housing development, and one with growing bipartisan support.

“Zoning is the biggest constraint on the supply of new housing,” she said. “Without changing the zoning no amount of new housing can be built — no new programs can succeed without changing the zoning.”