How homes catch fire

When a wildfire comes close, the wind throws burning bits of bark, twigs and leaves ahead of it. These embers can fly a long way and land on and around your home. If one lands on something dry, it can start a small fire, and that small fire can grow until it reaches your house.

Researchers at the Insurance Institute for Business & Home Safety (IBHS) found that embers cause up to 90 percent of the times a home catches fire in a wildfire. That is why the most important question is: where around my home could an ember land and catch fire?

1. Gutters full of leaves and pine needles. Gutters that are not cleaned out each year fill up with dry leaves and needles. An ember lands in them, they catch fire, and the flames sit right against the edge of your roof. Clean them out, and consider metal gutter covers.
2. Open attic and crawlspace vents. Vents let air in, and embers too. Once inside the attic, an ember can land on dust, insulation or stored boxes. Cover vents with metal mesh with openings no bigger than 1/8 inch.
3. A wood fence that touches the house. A wood fence is a line of fuel that leads straight to your wall. If it catches fire, it keeps burning against the house for a long time, long enough to set the siding and eaves on fire. Make the last 5 feet of fence next to the house metal or another material that won't burn.
4. Firewood stacked against the house. Firewood catches fire easily, burns very hot and for a long time, and is hard to put out: water runs off the outside while the inside of the pile keeps burning. A woodpile against the wall is like a campfire next to your house. Keep firewood at least 30 feet away; Washington DNR advises 100 feet for homes in the forest.
5. Bark mulch and bushes like juniper against the walls. Bark mulch catches embers easily, and some bushes, like juniper, catch fire easily too. Use gravel, rock or pavers in the first 5 feet instead.
6. Doormats, cushions, trash cans and other things by the door. Anything that burns, sitting next to the house, is a place for an ember to start a fire. Move them inside or away when fire is near.
7. Leaves and stored items under the deck. Leaves blow under decks and pile up where no one sees them. Embers end up in the same corners. Clear under decks and porches, and don't store anything that burns under them.

The other two ways a home catches fire

• Heat. A big fire nearby, like a burning shed, a car, a woodpile or thick bushes, can heat a wall or window until it catches fire or breaks, even without touching it.
• Flames touching the home. If plants, a fence or a deck lead right up to the house, the fire can simply burn its way there.

Spacing things out, and keeping the first 5 feet clear, protects against all three. See the three zones around your home.

Sources

• Embers cause up to 90 percent of home ignitions: IBHS, damage analysis of the 2017 and 2018 wildfires.
• Fencing within 5 feet of the home made of material that won't burn, including where it attaches; the first 5 feet and the area under decks kept clear of anything that burns: IBHS Wildfire Prepared Home, research.
• Gutters, 1/8 inch metal mesh on vents, metal gates within 5 feet, rock or pavers in the first 5 feet, removing bark mulch and junipers, clearing under decks: Oregon State Fire Marshal, Oregon Defensible Space.
• Firewood at least 30 feet from the house: Minnesota DNR Firewise guide (PDF); 100 feet for homes in the forest: Washington DNR (PDF).