How Car Parking Can Make Earthquakes More Dangerous in San Francisco

Can you tell why this building might collapse in an earthquake? Photo: Aaron Bialick

The threat of earthquakes that could destroy the homes of thousands at any moment has always loomed over San Francisco. In a bid to to reduce that risk, the Board of Supervisors is expected next week to mandate seismic retrofits for nearly 3,000 wood-frame “soft-story” buildings with five housing units or more that are potentially in danger of collapse.

But what may be overlooked in the discussion about earthquake safety is how it ties in with city parking policy: Many of the apartment buildings with weak ground-floor structures, or “soft-story” buildings, were built that way to make room for car parking.

“These are buildings that have larger openings on the ground floor, either due to garages or storefronts,” said Patrick Otellini, San Francisco’s director of earthquake safety. Many soft-story buildings were constructed before 1978, when modern engineering standards were set, he said.

Tom Radulovich, executive director of Livable City, explained that San Francisco set minimum residential parking requirements for new buildings in 1960, but those policies didn’t account for parking’s impacts on structural integrity. “If you’ve created a soft-story with parking additions, still in most places in the city there isn’t a way to get out of that, even if it compromises the safety of your building,” he said.

Radulovich said many buildings in American cities during the 1960s and 70s were built with ground floors completely devoted to parking, leaving little structural support, though they’re less common in SF, than, say, Los Angeles. For these buildings, he used the nickname “dingbat.”

Livable City has been working to reform provisions in the planning code in recent years to allow building owners more flexibility in removing or re-configuring parking to improve a building’s structural integrity, Radulovich said. As of 2010, developers can apply for an exemption from parking requirements if they can’t be met without compromising seismic safety. And tandem parking garages, in which multiple car owners park front-to-end in such a way that they rely on one another to move their cars for access, were legalized a few years ago at Livable City’s behest. That provision allows a garage to include the required number of parking spaces while taking up less space from the ground floor.

Otellini noted that most San Franciscans may underestimate how much damage a major earthquake could do, since they may only have only experienced quakes as big as Loma Prieta in 1989, which was only “moderate” in scale. That earthquake damaged the Embarcadero and Central Freeways badly enough to require their removal, and it sunk many houses in the Marina District, which sits on landfill. “This is not a Marina District problem. This is not a Mission District problem. This is a San Francisco problem,” he said.

“These types of buildings pose a serious threat, because there’s 58,000 San Franciscans that live in these buildings,” said Otellini. “If these buildings collapse, because it’s largely a rental [population], these are people that won’t come back to San Francisco.”

For a list of the nearly 3,000 soft-story buildings potentially at risk, read more at the SF Public Press.

  • GuestCommenter

    Absolutely.

  • Anonymous

    Yep. All over the East Bay too among mid-century buildings. Made buildings death traps to store a few cars.

  • Now the question is this, is there a way to reinforce these buildings to make them more stable? Giving up some of the parking space would probably be required, so I doubt many would be in favor of such work, especially if the costs have to come out of pocket.

  • davistrain

    Here in Southern California, the Northridge Quake back in 1994 demonstrated that “soft story” buildings are bad news in a major earthquake. I don’t remember the exact casualty figures, but as I recall, there were several fatalities blamed on weak underpinnings.

    One time when I was on jury duty in downtown LA, we had a long lunch hour, so I went over to the Pacific Stock Exchange building to see the trading floor. I was rather surprised to find that the first few floors were all for car parking, and one had to take an elevator to see where the action was.

  • I lived in Sherman Oaks during the Northridge quake, in an older building. We had a few minor cracks, but the brand new building right next to mine, which had underground parking, was red tagged.

  • Gilla

    Of course there is. You add a steel moment frame about the opening. It would only take up a little space, simply the width and depth of a steel columns. Depending on the structure, you may need several of these. And of course, steel isn’t cheap. It’s expensive to do, but not prohibitively. The issue isn’t so much the Code that required the parking (though I too believe we should not design buildings with parking) but that these building were built at a time when designing for earthquakes was poorly understood. New building with soft stories are now properly engineered for the additional loads.

  • I am less worried about whether renters in these buildings come back to San Francisco than I am with whether they will be killed in the event of an earthquake far more severe than Loma Prieta or Northridge. If the quake is big enough that, say, 2/3rds of soft-story buildings collapse, that means 2000 structures. If it happens at 5 am, that means most of the 38,000 people living in these structures will be caught up in a collapsed building. These are wood buildings, so they will have lighter rubble/debris than concrete/brick ones. Say after the quake 95% of the residents are conscious, unharmed enough, and under light enough debris to get out by themselves or with the aid of neighbors. That leaves roughly 1,900 who need serious help.

    We only have so many emergency personnel and equipment available to dig people out. Plus, the first 24 hours after a quake such personnel will likely be dealing with fires. After an earthquake, there’s only about a four day window to dig people out alive. The fewer the buildings that collapse, the fewer the people there are under rubble. The fewer the people under rubble, the higher the percentage of those trapped who will be gotten to in time. The fewer buildings that collapse also the fewer the fires that will start. The fewer buildings that collapse, the faster San Francisco as a whole will rebound after the quake.

    Though I can see why these seismic retrofits will be unpopular with building owners (and will eventually raise the rents in these structures) it is definitely in the best interests of the entire city that our building stock can withstand collapse in the event of a major earthquake. I only hope the structural engineers setting policy standards have been prudent enough, and all our collective retrofits will keep San Francisco standing.

  • In Santa Monica, after the 1994 earthquake, The city council mandated that all soft-story residential buildings be reinforced. Final approval was granted by a city
    inspector. Non-compliance ranged from strict fines to demolition!

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