Creating defensible space — Home hardening can save a structure from wildfire
BUFFALO — During a large wildfire event, it is often not a wall of flames but wind-driven embers that destroy houses and other infrastructure.
Matt Weakland, fire management officer for the Bighorn National Forest’s Powder River Ranger District, recalls working on the Marshall fire that destroyed more than 1,000 homes and killed two people south of Boulder, Colo. in December 2021. To him, that situation – the most destructive fire in Colorado history to date – was a lesson that in the arid Mountain West, most towns and properties are at risk.
“It was a grass fire that started quickly and spread in intense conditions and actually transitioned into the community. Then the homes and structures became the fuel that carried that fire,” Weakland said. “I would argue that every homeowner should consider construction materials and what they have around their home, because you never know what could come.”
So while wildland fire and land managers prepare for a potentially active fire season by staffing engines and crews and completing fuels-reduction projects, experts suggest that property owners make their own preparations too.
Most people think of defensible space as a necessity only on properties surrounded by dense forests, but the 2024 fire season proved that acreage in the sagebrush steppe and grasslands are also at risk.
During the House Draw fire that burned 175,000 acres, no primary structures were lost, but the fire did prompt evacuations throughout the county.
For Joel Thomas, wildfire prevention specialist with Bighorn and Shoshone national forests, data compiled by the insurance industry illustrates how home-hardening measures can protect primary structures in a wildland fire.
The space between within 5 feet of a structure is the most important area to consider in terms of defensible space in a wildfire event, according to Thomas and other local fire managers. A home and the space closest to it should have a roof and gutters cleared of dead leaves, debris and pine needles that could catch embers, according to the National Fire Protection Association. Flammable materials – plants, leaves and needles, firewood piles and anything else that can burn, should be moved away from the walls and nothing flammable should sit underneath decks or porches.
A study from the National Association of Insurance Commissioners shows that reducing vegetation in that zone nearly doubles a property’s wildfire survival rate.
Jacob McCarthy, Wyoming State Forestry District 5 forester, said that homeowners should consider that direct flame contact is not the only – or even the most common – way that structures are damaged in a wildfire.
“In most cases, it’s ember penetration into the structure that gets the structure involved,” he said.
The potential for ember ignitions during a wildfire event means that it is important to clean gutters and be mindful of where firewood is stacked, McCarthy and Thomas said.
“You see in the movies that it’s a big wall of fire that is destroying communities, and that’s just not the case,” Thomas said. “Stacks of firewood, you want to keep it nice and dry, but once an ember gets in there, it’s just a campfire waiting to happen.”
Other home-hardening measures to mitigate damage from ember wash include installing an 8-inch wire mesh behind vents to keep embers out.
“It’s more than just pine needles. I’ve seen pine cones get thrown a mile,” Thomas said. “It just depends on the intensity of the fire, and it just goes back to that zero to 5-foot ignition zone right onto your house. Even if you’re in the middle of town, you’re still susceptible to ember wash.”
Keeping grass green and mowed as much as possible is an important mitigation strategy in the 100-foot radius of a structure, Weakland said.
In the zone between 5 and 30 feet from a home, vegetation should be clear from underneath large stationary propane tanks and other fuel sources. Lawns should be maintained and vegetation should be removed from underneath trees so fire cannot reach the crowns. Tree canopies should also be at least 10 feet away from a house, and trees should be spaced so flames can’t jump from tree to tree. To interrupt a wildfire path and to keep flames closer to the ground, 30 to 100 feet from structures, there should be no heavy accumulations of ground litter and debris, and dead plant and tree material should be removed.
Ensuring that firefighters are able to access a home in a remote area is also an important consideration.
Weakland suggested that homeowners ensure that their roads and any bridges are in good, drivable condition, that there is a space to turn around near the structure and that there is enough clearance for large fire apparatus, at least 12 feet wide and 15 feet high.
“Firefighters are taught that in order to be at a structure when that flame front hits, there needs to be a safety zone,” he said. “Homeowners can set their homes up for success by creating those safety zone conditions at their home.”
Homeowners who make structural modifications to a home see a 40% improvement in a home’s survival rate, according to a study by the National Association of Insurance Commissioners.
Single-pane windows, which are common in older homes, can shatter if faced with high heat, Thomas said. Composite decking material may look nice, but it melts quickly and becomes flammable, Weakland said. The most fire resistant roofing materials include metal, clay, asphalt, concrete and tiles. Wood shingles are not recommended.
Addressing both vegetation and structural issues can result in a 75% risk reduction in a wildfire situation, Thomas said.
On the flip side, homes with heavy vegetation between zero and 10 feet from a home have a 115% higher wildfire claim frequency and a 272% higher loss ratio than homes with defensible space.
Properties within the wildland-urban interface, the area where houses and undeveloped wildlands meet, are considered to be at the highest risk of wildland fire. At this point, there is no strict definition of the wildland-urban interface, or WUI.
Weakland said that for the local Forest Service office, any place where human development – a cabin, home or communication site, for example – interacts with the wild land is the WUI. When Thomas talks with homeowners, he describes it not as a geographic location but as “a set of conditions that can exist in many communities.”
“Anybody who lives in this part of the country is basically there,” he said.
Weakland said that the Forest Service, for its part, has focused on fuels reduction around structures on the Bighorn National Forest.
“It does take everybody working together to honestly protect homes in a wildfire situation,” he said. “And the more pre-work that we do, both in the vegetation and the home, the more likely those homes are to survive a wildfire event.”
Consulting with the experts
The National Fire Protection Association on its website breaks defensible space into three zones and is considered the most comprehensive source on defensible space and home hardening for wildfire mitigation. More information is available on the organization’s Firewise program website, nfpa.org.
The U.S. Forest Service and Wyoming State Forestry are agency resources for homeowners when it comes to defensible space and home hardening.
Joel Thomas, wildfire prevention specialist with Bighorn and Shoshone national forests, said that Forest Service personnel are available to assess properties close to national forest boundaries.
Jacob McCarthy, Wyoming State Forestry District 5 forester, works with private landowners to determine best wildfire mitigation practices. Contact Wyoming State Forestry at 684-2752.
This story was published on April 9, 2026.