National Geographic News
Homes burn in the Smiley Park neighborhood of Running Springs, CA during the Slide Fire in 2007.

Scientists have learned more about how to keep homes safe from wildfires. During 2007's Slide fire, firefighters decided conditions were too dangerous to defend this home in Running Springs, California.

Photograph by Mark Thiessen, National Geographic Creative

Warren Cornwall

for National Geographic

Published July 30, 2014

When a wildfire swept through 2,000 acres in the hills north of San Diego, California, in May, it left behind a curious checkerboard of destruction. One neighborhood was reduced to ashes and twisted metal. But houses nearby suffered little more than scorched grass and singed trees.

Captain Richard Cordova of the state firefighting agency, Cal Fire, visited the scene and quickly hit on one explanation for the fire's apparent favoritism.

Many of the homes that survived had little flammable brush in the area immediately around them. But others had dry grass and shrubs within feet of the walls. "Those were the ones that unfortunately did burn down," Cordova said.

As the summer wildfire season enters full swing in the United States, with more than 700,000 acres now burning in the Pacific Northwest and California, the difference between a surviving house and a charred husk could come down to details as small as screens over attic vents, trimmed trees, or pine needles in the gutters.

In fact, in the past ten years scientists have gained a whole new understanding of factors that can help a home survive a wildfire. And it turns out that saving a house has less to do with stopping a forest fire cold or creating a nonflammable moonscape for a hundred feet in every direction. It's more about lots of minor modifications and regular maintenance.

"It's the little things," said Michele Steinberg of the National Fire Protection Association, whose Firewise program works to educate American homeowners and communities about protecting themselves from wildfires. "That's the surprising fact for folks. I'm thinking I have to chop down every tree in the forest to protect my home, but what's really going to get me is the mulch up against the house or the doggy door that isn't sealed."

As wildfires grow bigger and more intense—the product of drought, disease, climate change, and buildup of flammable material from decades of extinguishing nearly all fires—and annual federal spending on firefighting surpasses one billion dollars, the new science of fireproofing has some experts asking if federal, state, and local agencies should be steering more money toward making homes and communities fire resistant.

Jeff Brown waters the roof of his home as vegetation smolders during a wildfire, Thursday, May 15, 2014, in Escondido, Calif.
In Escondido, California, Jeff Brown sprays water on the roof of his house on May 15, 2014, to stave off nearby wildfires.
Photograph by Gregory Bull, Associated Press

Evolving Science of Fireproofing

For Steve Quarles, the new thinking on fireproofing crystallized in 2003, when he was sifting through ashes from the massive Cedar Fire in southern California. The blaze destroyed 2,200 homes, killed 15 people, and helped introduce the term "fire siege" into the local lexicon. Then a scientist at the University of California who was studying what happened to structures in wildfires, Quarles found green bushes and blooming flowers next to houses reduced to cinders. How would a fire leave such an odd pattern?

He went looking for a culprit that could set a house on fire without torching everything around it. He found it in tiny embers, or firebrands, as they are known among wildfire scientists. Blown far from a wildfire by the wind, these bits of burning debris can wreak havoc if they collect in flammable spots around a house: a gutter filled with pine needles, an unscreened vent leading into an attic, or a trash can left open against a wall.

That's different from an older belief—one still widely held by the public—that a wildfire's dramatic, towering flames march through a neighborhood, incinerating buildings in their path. Earlier scientific research into home destruction during wildfires had focused on how close a sustained fire, like a burning bush, needed to be to a home to set it ablaze.

But firebrands can shower a house that's situated a quarter mile or more from a wildfire. So they've become a central focus for Quarles, who now spends his days searching for the chinks in a house's armor as a senior scientist at the insurance industry-funded Insurance Institute for Business and Home Safety.

At a massive wind tunnel laboratory in South Carolina, he tries to set houses on fire. To figure out where firebrands cause the most problems, he builds small fires in a series of metal barrels, then lets a fan blow the firebrands onto a full-size house built inside the wind tunnel.

Carol Brown, right, is hugged by a friend as she looks at the charred remains of her home in Cuyamaca, Calif. Nov. 1, 2003.
A pair of friends stand among the charred remains of a house in Cuyamaca, California, one of 2,200 homes destroyed by the Cedar fire in 2003.
Photograph by Charlie Riedel, Associated Press

Mulch to Kindling

The experiments produced some surprising results. For one, landscaping mulch around houses turns into kindling when an ember lands there.

But the experiments also suggested that tiny modifications to a home can make a big difference. For instance, a metal cap can block embers from sneaking into the space between the roof and the fascia—the horizontal board ringing the roof's edge. Screens with gaps no bigger than one-eighth inch can stop embers from getting through vents leading to crawl spaces and attics.

Joe Stutler is putting that science to use on his home in the dry forests outside Bend, Oregon. A career firefighter with more than three decades of experience with federal wildfire-fighting agencies, he has stone pavers instead of a wooden deck, gutters designed to shed pine needles, a fire-resistant roof, and stone siding at the bottom part of the house's exterior.

Farther out, he's planted grass along the side of the house where a fire is most likely to come from, mowed the wild grasses to four inches high, and cut off the low-hanging limbs on evergreens to keep a grass fire from climbing into the treetops.

But he also knows his home's survival depends partly on what his neighbors do. If a single home catches fire, it can fling embers onto nearby houses. In dense developments, the heat of a burning house can ignite the house next door, setting off a chain reaction that overwhelms firefighters.

So Stutler, who advises his local county on wildfire policy, has rallied his neighborhood. Federal grants pay for free collection of flammable debris that homeowners rake from their yards in the spring. The grass and shrubs in vacant lots are mowed each year.

But he only has to drive to a nearby subdivision for a different picture. "Half of them have bitterbrush—what I call gasoline on a stick—growing over my head," he said. "It's just a matter of time before we have a significant fire and it burns a bunch of houses."

Watch a wildfire ember demonstration conducted by the Insurance Institute for Business and Home Safety.

Fight Fire With Fire

So far, government spending on making homes more fire resistant has lagged far behind the amount expended on fighting wildfires. In 2013 the U.S. Forest Service spent more than $1.3 billion putting out fires. It spent just $2.6 million helping communities adapt to fire, and doled out an additional $24 million to states for similar programs and for clearing fire-prone forests.

The sharp funding imbalance frustrates Jack Cohen, a Forest Service scientist and one of the leading experts on wildfires and houses. The fear of forest fires consuming homes has helped drive decades of costly efforts to squelch nearly every blaze, he said. That policy has denied forests the natural fires that helped shape the landscape for eons. One result: forests cluttered with dead or overcrowded timber thats feed huge, intense fires.

Rather than focusing so much on putting out fires, Cohen said, attention should be paid to creating communities that can pass through a fire relatively unscathed. That would mean looking at the area right around houses, and at the structures themselves. (See: "NEXT: Simulating Wildfires.")

Cohen has repeatedly been called to the scene after a wildfire destroys homes around the West, to help figure out what happened. It nearly always comes down to homes and neighborhoods that weren't built or maintained to weather a fire.

"Basically, it's time to admit that there are going to be fires that we can't deal with, and ... we need to be compatible and not controlling," he said. "This is a home ignition problem, not a wildfire problem."

Graphic: Don't Fan the Flames

Each year more Americans move into what is called the wildland-urban interface: zones where human habitation meets forests or grasslands. Many wildfires start in such places; under the right conditions, flames or embers can easily spread to nearby homes. Fortunately, there are ways to make a house in those zones less vulnerable to fire, from the choice of building materials to the landscaping decisions. More information is available at
1 Improve the Roof
Fire-resistant ceramic tiles, slate or composition shingles, and metal sheets provide better protection than wood.

2 Seal Off Openings
Put metal screens over vents and other openings to block embers.

3 Prune Branches
Flames can jump from branches hanging over the roof of the house.

4 Mow the Lawn
Keep grass short and well watered to hinder the spread of flames.

5 Pick Up Debris
Remove leaf litter and pine needles from gutters, dead limbs from around the house.

6 Lighten Landscaping
Spacing out trees and shrubs makes it harder for flames to travel and easier for firefighters to work.
Art explaining how to make a house more fire-resistant.
art: mika grondahl

Follow Warren Cornwall on Twitter.

Lawrence Crushing
Lawrence Crushing

In an effort to help combat fires, roofing components are now coming fireproof and fire retardant. According to Schulte Roofing, most homeowners want class IV fire rated roofing materials. The best kind of roof for fire is also metal. For those with cedar or wood shake roofs, there are special coatings that you should apply ever year to help prevent fires from starting from embers.

Bill Capel
Bill Capel

Pretty good introduction to fire mitigation. The best book on this topic is "The Fire Smart Home Handbook: Preparing for and Surviving the Threat of Wildfire." It covers every detail of what to do before, during, and after a forest fire. There's a lot more to it than "common sense," though that sure helps.

Robertico Henderson
Robertico Henderson

Science? what happened to common sense?. Don't have any fuel around your house and if you do, respect the fire and keeps lots of water around you. Ahhhh  the science of common sense. Fire crews need to clear around the houses during down times and send the property owners the bill. ta tahhhhh common sense.

Karma Bennett
Karma Bennett

Great article! I've been reading up on to learn about this topic. The guy who runs that site offer tips for both the dry AND the wet season---wildfire protection is a year-round activity. 

Marianne Smith
Marianne Smith

One more thing to think about. I returned to my house after a short evacuation. Stepping out onto the covered patio, I saw a blackened leaf, about 4" X 2", lying on top of a patio chair cushion. If the cushion had caught, the flames could have reached the patio cover, a wood and asphalt shingle roof attached to the house. Yikes! Added to the list of things to do when evacuating.

Kathy Holcomb
Kathy Holcomb

This is an outstanding article!  Thank you!

Debbie Henson
Debbie Henson

Excellent article! Lot's of very useful information to protect homes against fire.

Richard Halsey
Richard Halsey

This is EXCELLENT! National Geographic is really getting ahead of the curve when it comes helping the public and fire agencies understand the science in order to save homes from wildfires. Thank you!

For more on the subject, we have a list of research papers and other materials on our website that can be useful to creating fire safe communities:

Geoff eagar
Geoff eagar

IN Australia the threat of bushfires has been built into our collective consciousness such that governments of all persuasions have supported the science of effective preparation of houses and communities for bushfires.

See here:

David Jones
David Jones

I don't think that the Federal government needs to expend a lot to increase fireproofing of communities. It seems a problem best addressed by local communities, construction and real estate groups and landscaping firms. The Federal government certainly could have a useful role in disseminating information though and certainly these steps could be applied to the thousands of Federal facilities including military bases to good effect.


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