Building with Wildfire Resilience in Mind

This guest blog appears courtesy of LGA Studios

There’s so much to think about when building your home, but structural stability is one of the most critical considerations. Fortunately, this is also an area of continuous advancement in the building industry, the result of lessons sometimes learned the hard way through natural disasters, whether they be fires, flooding, wind, or earthquakes. In our Rocky Mountain region, the most common trial has been wildfires. 

Given the hot, dry summers and occasional gusty high winds—capable of carrying embers for miles in the right conditions—many states including Colorado and California remain in constant danger of home-threatening wildfires. 

Because the annual threat of wildfires isn’t going away anytime soon, it’s worth it to look at ways to mitigate risks and to rebuild smarter, making use of hard-fought knowledge and new technology.

In this blog, we take a look at how our local Colorado Springs community has been learning and improving our city’s code following a series of devastating wildfires.

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In 2002, the Hayman Fire destroyed 133 homes outside of Colorado Springs, rapidly covering 19 miles in just one day out of a three week burn period. After that fire, the city banned wood-shake roofs for all new homes and re-roofs, a major step forward in making home construction more resilient. But dense vegetation can be a major concern as well, particularly underbrush and trees with low limbs that aren’t pruned back, and with the amount of flying embers a fire can produce, limiting or regularly clearing dense, dry vegetation can provide critical defensible space and prevent fires from spreading to engulf blocks of homes.

The Waldo Canyon fire in 2012 ravaged 346 Colorado Springs homes in mere hours, completely destroying entire neighborhoods in the Mountain Shadows area. Only a year later, in 2013, Colorado Springs was hit by yet another wildfire—the Black Forest fire—which burned 500 structures.

Immediately after the 2012 Waldo Canyon fire was contained, Colorado Springs Fire Marshal Brett Lacey assembled a task force of builders and homeowners to amend the city’s fire code, resulting in “Appendix K,” an amendment specifically aimed at keeping communities and first responders safer. This included requiring “Firewise” vegetation management techniques in the burn area, as well as increasing the number of fire-resistant construction details in rebuilt homes.

Concrete decks, stucco and stone finishes, and minimal, well-maintained vegetation all contribute to wildfire resilience.

In terms of style and curb appeal, fire-resistant finishes have long been favored in Colorado, with many clients already opting for the low-maintenance appeal of stucco and stone. Colorado also has notoriously awful hailstorms, meaning fiberglass shingles and concrete tile have been used over less durable wood shakes for many years now. 

When designing your home, think about ways to make it more resilient, more eco-friendly and lower-maintenance. More often than not, these traits will go hand in hand and will complement each other, giving you a home you can enjoy for many years to come.

APPENDIX K SPECIFICATIONS FOR IGNITION-RESISTANT BUILDINGS

These specifications come from Colorado Springs’s Appendix K, summarized expertly in Ted Cushman’s article “Living with Wildfire” in the September 2017 issue of The Journal of Light Construction. LGA Studios worked extensively with many homeowners who lost their homes in Mountain Shadows and Black Forest, designing homes that are up to the new code. One of the home building contractors LGA Studios works with is Andy Stauffer, who was interviewed in the article.

ROOFS: Appendix K requires Class A roof systems. The Class A rating is based on laboratory testing of roof assemblies, in which a large criss-cross lattice of burning wood is placed on the roof covering and allowed to burn out. The material passes if the sheathing is not ignited. Clay tile, concrete tile, slate, and metal roofing typically comply, as do most fiberglass asphalt shingles.

ATTIC VENTS: Roof vents have to be screened with wire mesh or hardware cloth, with openings no larger than 1/8 inch. The 1/8-inch opening size is typical of all the well-known wildland-urban interface codes. According to wildfire expert Steven Quarles, who helped craft California’s wildfire code before joining the Insurance Institute for Building and Home Safety (IBHS), an insurance industry think tank, 1/8 inch is a compromise. While the mesh may let small sparks through, it will hold out the bigger embers that carry the most heat. At the same time, the holes are big enough that they’re less likely than finer mesh to become plugged with paint or dirt over many years in service.

EAVES AND SOFFITS: Soffits and fascia should be built with ignition-resistant material such as fiber cement or metal. Decorative features like false rafter tails are allowed to be made of wood or other combustible materials, but the fire service strongly urges builders to choose ignition-resistant options whenever possible.

GUTTERS: The big risk posed by gutters isn’t the gutters themselves, but the flammable materials, such as leaves and pine needles, that accumulate in them and that can readily catch fire when windblown embers land there. When that happens, vinyl gutters typically melt and fall off, posing a risk of ignition at the base of the house. Metal gutters stay in place, which allows burning debris to ignite the exposed edges of roof sheathing.

Appendix K doesn’t require debris screens over gutters, but the fire service cautions homeowners that gutters should be kept clear of combustible materials. Appendix K does require roof sheathing and framing to be protected against ignition by metal flashing at the roof’s edge that extends down into the gutter. In the case of vinyl gutters, the rule requires noncombustible ground covering, such as stone, at the base of the wall where flaming gutters might fall.

CLADDING AND SIDING: Exterior cladding in the wildfire-prone area must be ignition-resistant. Approved materials include fiber cement, stucco, masonry, and manufactured stone. Natural wood, hardboard, and vinyl are prohibited.

OVERHANGS AND PROJECTIONS: The exposed undersides of building projections such as bay windows are vulnerable to ignition from burning vegetation or accumulating embers. Appendix K requires these surfaces to be protected with the same type of material that is approved for wall cladding.

EXTERIOR DOORS: Appendix K requires doors to be noncombustible or, if wood, to have solid cores at least 1 3/4 inches thick. Any glass in the door must be either tempered safety glass or multilayered glazing, with one exception: Front entry doors are allowed to incorporate decorative single-pane glass.

WINDOWS: Windows must be dual-pane. Research has shown that dual-glazed windows can survive intense radiant heat in a wildfire (typically, outer panes crack and break while inner panes survive). Tempered glass has proven to be the best performer in practice, as well as in laboratory testing. Wildfire expert Steven Quarles points out that even before wildfire codes began to take effect, code has required tempered glass for certain windows, such as windows close to the floor or next to stairs. So most window companies have had no difficulty making dual-glazed tempered options available where needed to make a home ignition-resistant.

DECKS: Brush and trees near a deck can readily set it on fire, as can combustible material such as firewood stored under a deck. Windblown embers can also ignite a deck, but in the Waldo Canyon fire and other fires, composite decking proved less likely to ignite than wood decking, which tends to split and crack and catch hot embers. Appendix K requires ignition-resistant or noncombustible material for decking, but allows wood framing for the deck structure.

BASE OF WALLS: Embers piling up against a house can set the exposed bottom edge of wall sheathing on fire, even if the cladding is noncombustible. Appendix K requires wall bases to be protected with fire caulking (or 1/8-inch wire hardware cloth, if weep holes are needed). Full-scale laboratory research at IBHS has shown that a 6-inch separation between combustible siding and the ground is enough clearance to sharply reduce the risk of fire from embers at the base of the wall.

For more on wildfire resilience, see Living With Wildfire, from The Journal of Light Construction.

For further inspiration, you can also learn about the specific materials chosen and steps taken at the Getty Center in Los Angeles that ensured the priceless art held there remained perfectly safe as the recent Skirball Fire raged less than a mile away: Why the Getty Center's Art Stayed Put as Fires Raged Nearby, from The New York Times.

Photo by Michael Held on Unsplash