Can We Design California Houses So They Don’t Burn?

Can We Design California Houses So They Don’t Burn?

26 November 2018

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USA – Some survivors of California’s Camp Fire realized it was time to evacuate because they heard propane tanks exploding nearby. A wildfire arriving in town sounds different than it does in the forest—and behaves differently too.

California’s recent string of wildfires is the result of an environment changing in ways that are beyond our immediate control, and expected to continue. But when a fire arrives in a place like Paradise, a town of 26,000 now all but reduced to ash, it takes on a new character. “It was an urban conflagration,” Jonathan Pangburn, part of the California Department of Forestry and Fire Protection’s incident management team, told the LA Times. “It was structure-to-structure-to-structure ignition that carried the fire through this community.” Paradise was leveled. But just above, the needles on the big ponderosa pines didn’t even burn.

Nearly 16,000 structures have been destroyed in the Camp Fire, the deadliest and most destructive fire in the history of California. (The next nine worst blazes in the state together destroyed 20,500 structures.) The devastation is in part a story of how climate change–induced “boom and bust” cycles of rainfall and drought have made firetraps of California forests. But it’s also a story about the way we build.

Despite its image of self-reliance and individualism, the American West is the most urban region of the United States. The hinterlands are sparsely populated; the metropolitan areas are huge. In the 2010 census, California reported the highest share of urbanized residents of any state. (The top 10 also includes Arizona, Nevada, and Utah.)

But more and more Westerners are trying to live with nature. In California, the number of housing units in the wildland-urban interface, or WUI, has crept up from 3.3 million in 1990 to 4.4 million in 2010. Comparatively speaking, it’s not a high number—a far greater share of Americans live in nature in Connecticut or North Carolina. But this is the West, and the wildlands here burn. With an estimated 11 million Californians living in nature, retreat is unthinkable. The state will have to build its way out.

Nothing new about that. The American city is the box score of a tennis match between fire and architecture. It’s no surprise that the best maps of cities of the late 19th century were made by Sanborn, the fire insurance company. A few decades earlier, Chicago homebuilders began using a technique called “balloon-frame construction,” replacing cumbersome erections of beams and joists with rapidly built skeletons of precut lumber and nails. The balloon-frame house revolutionized construction, making it so much faster and easier that Chicago could grow from 30,000 people in 1850 to 300,000 in 1870—and set the stage for the Great Fire of 1871, in which flames devoured the new builds. The innovation in fireproofing that occurred as a response is what made the skyscraper possible.

But even fireproof high-rises could burn, as New York discovered during the 1911 Triangle Shirtwaist Factory fire, when 146 workers died in a sweatshop on the top floors of a 10-story Greenwich Village building. Thanks to the new construction standards, the fire did only superficial damage to the building, which still stands today. But the tragedy prompted a national revolution in building codes; in New York, lawmakers required the enclosed, fireproof stairways that would enshrine the stairs’ hidden, subservient place in the modern high-rise.

The fall of the urban fire is at least partially attributable to the fact that Americans have far fewer open flames at home and at work now than they did then. Still, one sign of the success of those regulations is that only two U.S. high-rise fires have surpassed the toll of the Shirtwaist Factory fire: the Oklahoma City bombing and the Sept. 11 attacks on the World Trade Center. Those, in turn, have made their mark on the city; the quip is that no architect has had more influence on the 21st-century American city than Osama Bin Laden.

No such catastrophe has made its mark on the homes of the wildland-urban interface—yet. Climate change aside, the modern history of wildfires in the West is sometimes framed as a story of historic mismanagement—of forests that weren’t allowed to burn or, more recently, of pine needles that weren’t raked. But Jim Webster, who runs a mitigation program for vulnerable houses in Boulder County, Colorado, says the focus should be on the way we build: “If you want to talk policy, our main response is suppression, our second is forest management, our third is hardening homes. We think that’s the most important, but it receives the least attention. We have the technology to build homes with very low ignition potential. They’re a little more expensive to build in the beginning, but they don’t ignite in the long term.”

The question of cost looms large. In California’s WUI there are mansions in Malibu, ranch homes in Sonoma, and trailers in the foothills of the Sierra Nevada. Wealthy homeowners invest in new, synthetic materials to fireproof their homes; poorer survivors wonder whether it’s worth rebuilding at all. It is hard to generalize about the massive, at-risk population: In some Western states (Colorado, Nevada), WUI homes are more valuable than the average; in others (Arizona, Oregon), they are worth less.

California has, since 1991, enforced a strict building code for new structures in the WUI, with an eye toward clearing out the “home ignition zone” where a wildfire becomes a structure fire. Wood siding is not forbidden, but it has to be flanked with noncombustible gypsum board. Wood shingle roofs are banned. Air vents, which take in floating embers that can ignite homes from the inside, must be tightly screened.

But even this WUI code hasn’t kept California houses from burning. There are several reasons for that. For one thing, many, many structures predate the code and retrofitting presents a formidable financial obstacle. Homeowners or tenants may fail to keep the property in shipshape, stacking firewood against the house, letting bushes grow, or leaving the garage door open. After disasters, getting people housed often takes priority over building strictly to code—and contractors and insurance companies are striving for the cheapest possible build.

Fireproof architecture also has its limits. “Concrete is not going to burn,” noted David Wilson, a Bay Area architect who has worked in the WUI. “But the window gaskets will melt. The windows will melt. Your plumbing and electrical will melt.”

It’s not all about architecture. The biggest development of the past few decades may be the emphasis on “defensible space”—clearing the land around the house and the property like a moat. “Religious” brush clearance has been a saving grace of Pepperdine University, in Malibu, which survived the recent Woolsey Fire intact.

But there is no way to maintain effective defensible space in communities where each house is 20 feet from the next, and your house is only as strong as the one next door. In a state with some of the highest land values in the country, not everyone can have a Pepperdine-style grassy meadow around their home. Some architects think the long-term solution lies in more intelligent land use: building denser, protected settlements in the WUI with huge, public firebreaks—like medieval towns. This would also make firefighting a more concentrated and efficient pursuit. The requisite rearrangements of property ownership make such an idea nearly as far-fetched and challenging as managed retreat. (On the East Coast, beach towns can barely build dunes without yearslong struggles that end in eminent domain.)

If there’s a new fireproof architecture, it might look like the Glen Ellen Retreat, a home the architect Brandon Jorgensen is designing for a volunteer firefighter in Sonoma County, where last year’s Northern California wildfires killed 44 and burned 245,000 acres north of San Francisco Bay. The house has the air of a slightly militarized modernist villa. “We’ve designed the house to have a fire burn over and around it,” Jorgensen told me. There are no vents for embers to creep in and burn the house from the inside. Mechanized fire shutters are tied to infrared sensors. “It essentially could survive four hours of nonstop assault.”

A year from now, Jorgensen hopes to stage a fireproof house tour with other architects who are trying out new designs and materials in the area. Even putting the cost aside, though, it is hard to envision projects like this as blueprints for a statewide, vernacular fireproof architecture. One fortress, among the more than 4 million houses in the WUI, might outlast a fire—only to end up the equivalent of the famous Mexico Beach house that survived Hurricane Michael. Triumphant, and alone in the ruins.

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