Much of San Francisco's built form has been shaped by policies and zoning laws which restrict the scale, density and heights of new development in order to protect the city's enviable natural surroundings. Yet the burgeoning housing crisis may force the city to take another look at these policies. 

Downtown San Francisco, image by Jack Landau

Downtown San Francisco is not unlike the downtowns of other large American cities. It is populated by skyscraping office, hotel and condominium towers with no shortage of shopping, dining and entertainment options at ground level. Outside of the core, the urban fabric of the city changes dramatically. Soaring highrises are replaced with two- and three-storey buildings that comprise the quirky and eclectic neighbourhoods for which San Francisco is known. The idea of developing these neighbourhoods with shiny new midrises, or something even taller, is a worry among many who want to preserve their unique character. 

Current zoning regulations limit the height of buildings to only 40 feet in the vast majority of the city. Those regulations arose partially from the desire to shield public parks from shadows and maintain the impressive views that the city's steep hills offer. 'Sunset zoning' prescribes that buildings cannot cast shadows on parks or squares for more than an hour during the day. That puts strict limits on the ability of developers to build high towers. The map below by San Francisco housing advocate Mike Schiraldi shows the situation; everything in yellow is restricted to 40 feet and lower. 

San Francisco zoning height map, image by Mike Schiraldi

While this arrangement might have been sufficient in the past, San Francisco's growing population is putting stress on housing needs. The success of local tech giants, from Twitter to Apple, has translated to high wages for its employees, who can pay a premium to live in one of the country's most vibrant cities. This increased demand and a lack of overall housing supply have left San Francisco with the highest rent prices in the United States. 

There's only so much room for San Francisco to grow. Since it's situated on a peninsula, the city's geography places physical constraints on where building can occur. Urban planners recognize that sprawl has negative effects on quality of life, which San Franciscans hold dear. That leaves little choice for a city which is expected to hit a population of one million in 15 years. 

This lowrise character is common throughout San Francisco, image by Jack Landau

While the housing supply issue has been gaining more attention in local media, in some ways, zoning is becoming even more restrictive. In 2014, residents voted in favour of Proposition B, which requires developments to seek approval directly from voters for all projects exceeding the current height limits, ranging from 40 to 90 feet, along a 7.5 mile stretch of San Francisco waterfront. 

There have, however, been signs of upzoning. The Transit Center District Plan has paved the way for the Transbay Transit Center and a host of new towers. Several development sites, including 181 Fremont, 350 Mission Street and the Salesforce Tower, all saw their maximum heights raised:

The former and now approved height limits, image courtesy of the San Francisco Planning Department

The 2008 Market and Octavia Area Plan raised some of the allowable heights in that neighbourhood to 400 feet. Planning Director John Rahaim has put forth the idea of raising those limits once again in an effort to build more affordable housing. 

San Francisco's Inclusionary Affordable Housing Program mandates that developers seeking to build 10 or more residential units pay an Affordable Housing Fee or make arrangements for low- and moderate-income housing within their project or a development off-site. An increase in development activity would then lead to an increase in affordable housing. 

Shaded areas where the bonus density program would apply, image courtesy of the San Francisco Planning Department

San Francisco's Planning Department has also proposed legislation that would give new developments in some areas an extra two storeys or relaxation on other zoning regulations in exchange for more affordable housing. The density bonus would allow affordable housing projects to reach three storeys beyond the current maximum. If approved, it would send a clear signal to residents, and those hoping to become residents soon, that planners and politicians are serious about addressing the housing gap. 

Other American cities, including Washington D.C. where the city skyline is fairly flat, are feeling the pinch as well. They are facing the same questions and difficult decisions as San Francisco. But San Francisco can lead the way by showing that preservation of the city's impressive lowrise architecture can coexist with a mandate for increased density.