Understanding Why Some Homes Survive Wildfires While Others Don't
Emails and videos of burned buildings in Los Angeles next to those left standing have sparked discussions among architects, builders, and fire safety specialists around the world. Homeowners often attribute the survival of their homes to luck, but experts
Real Estate:WASHINGTON, Jan 19 Emails and videos of burned buildings in Los Angeles next to those left standing have been circulating among architects, builders, and fire safety specialists worldwide. For many homeowners, such as Enrique Balcazar, the seemingly random destruction can seem like a matter of luck. Balcazar, a real estate agent, posted a video showing his neighbor's destroyed classic Mustang and the charred remains of most homes on his block, yet his home was largely unscathed. 'It’s an older house and it still has the old wood sidings,’ Balcazar said. ‘There’s nothing explainable in logical or scientific reason of why my house would not have burned.’
Many experts say luck does play a part. Wind can shift 180 degrees in a split second, pushing fire away from one house and towards another. However, there are several ways to make homes less vulnerable to fire. ‘Because there are, say, 50 ways a fire can burn your house,’ said Greg Faulkner of Faulkner Architects in California, who has focused on less combustible home exteriors for over a decade. ‘If you eliminate half of those, or three-quarters of them, that’s not luck, that’s increasing your odds.’
People in fire-prone areas generally know that trees, landscaping, and wood fences near homes can be fire risks. Architects and contractors are going beyond this, using newer materials and techniques in roofing, walls, and windows to keep buildings standing. These measures can add 3% to 6% to the cost of a home, or as much as 10% for the most robust protection, according to Faulkner.
Many experts no longer use wood siding. Where it is used, or still allowed, it needs to have a fire-resistant barrier underneath, often made of gypsum, the same material used to make drywall. This ensures that if the wood catches fire, it takes longer for the heat to reach inside the home. However, even with this barrier, you’re still putting a combustible material on the building, said Richard Schuh of Nielsen Schuh Architects. ‘So that would be something we would avoid. Use of fire-resistant materials is critical.’
Stucco, a cement material, is a common exterior for Southern California houses and is fire-resistant. Arnold Tarling, who has four decades of experience in fire protection and building inspection in Britain, noted that houses with stucco walls appeared to survive the Los Angeles fires better. However, if more of them had a layer of gypsum beneath the stucco, it would have provided even more protection from the heat.
Windows are a significant factor in whether a home burns down, as they transmit a lot of heat. Double-pane windows significantly slow heat coming from a burning building next door. ‘The outside layer protects the inside layer until it fails,’ said Schuh. Codes in many places require one of the two panes to be tempered, which is much more resistant to heat than conventional glass.
Tarling noted one intact Malibu beachfront home surrounded by gutted buildings. He speculated that the fact that no windows faced a neighbor helped protect it because radiated heat couldn’t penetrate as easily. In his buildings, Faulkner includes fire shutters that can slide closed and cover the windows.
Roofs are another critical area, often serving as a convenient landing pad for fire embers. Simpler roof lines can allow red-hot embers to slide off. The Spanish Mission style, common in Los Angeles, features knee walls that create corners where embers can gather. ‘The embers could, just like snow, gather in that corner,’ Faulkner said.
Many roofs in the US are covered in asphalt. In areas designated as wildfire-prone in California, roofing that delays the transfer of heat to the inside of the building, known as one-hour or Class A, is required. While asphalt is a petroleum product, some building professionals prefer metal, which doesn’t burn. However, metal conducts heat, so a layer of gypsum under a metal roof is becoming a common practice in some areas.
Roof ventilation is another important consideration. Contractors ensure air circulates in attics to prevent moisture buildup, but in a powerful fire, this can backfire. ‘If you’re on the side where the wind is putting pressure against the house, it’s also blowing the flames into the house like a blow torch,’ said Schuh. On the other side, it can create a vacuum, sucking fire in. However, eliminating roof ventilation can cause moisture problems. Faulkner is eliminating the need for ventilation in the roof structure by sealing the spaces, while Schuh uses a cover on roof vents that can respond to fire with a mesh that closes.
In some parts of Australia, new homes are required to have water tanks. ‘If each home has the ability to protect itself, fire won’t be able to spread as much,’ said Cesar Martin Gomez, an architect at the University of Navarra, Spain. In the US, some homes are now built with sprinkler systems for the outside of the house, not just the inside. These systems spray water with a soapy solution to make it flow over the surface of the building, adding an extra layer of protection. ‘You’re adding one more layer of protection to your building, and that’s more of a priority now than ever because your insurance company may or may not be around for you,’ said Schuh.
Frequently Asked Questions
Why do some homes survive wildfires while others don't?
Some homes survive wildfires due to a combination of luck and proactive fire-resistant design and materials. Factors like stucco exteriors, double-pane windows, and simpler roof lines can significantly reduce a home's vulnerability to fire.
What are some fire-resistant materials used in home construction?
Common fire-resistant materials include stucco, gypsum barriers under wood siding, and metal roofs. These materials can slow the spread of fire and protect the interior of the home.
How do double-pane windows help in fire protection?
Double-pane windows significantly slow heat transmission from a burning building next door. The outer pane protects the inner pane, delaying the point at which the heat can reach the interior of the home.
What are the advantages and disadvantages of metal roofs in fire-prone areas?
Metal roofs do not burn, making them a good choice for fire protection. However, they conduct heat, so a layer of gypsum is often added under the metal to provide additional insulation.
Why is proper roof ventilation important in fire-prone areas?
Proper roof ventilation is crucial to prevent moisture buildup in attics. However, in a powerful fire, it can also create a pathway for flames to enter the house. Some architects are using covers on roof vents that can close in response to fire.