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How Homeowners Can Help Protect their Properties from Wildfire

October 20, 2020

The Western U.S. saw another summer of devastating wildfires this year. Thanks to research on these and past fires, we have more evidence that building construction helps prevent property damage. That research builds on existing knowledge about the value of maintaining the area around a home and building construction codes.

These aren’t the only factors affecting property damage risk, and some homes and other structures may burn even when each factor is optimized. Still, these factors all play important roles in reducing property risk from wildfires. We’ll cover each and give you resources to share with your homeowners policy customers so they can better protect their homes.

What is home hardening and why does it matter?

A hardened home is built and maintained to withstand risks posed by natural disasters, such as earthquakes, floods, hurricanes and wildfires. The steps taken to harden a home vary based on the relevant risk. Foundation strapping helps prevent earthquake damage, for example, but won’t help prevent flood damage.

A home hardened against wildfires is built with materials that are less likely to ignite and burn — even if they’re exposed to embers or flames — and has well-maintained space surrounding it. Many homeowners may think flame spread is the biggest risk, but fire scientists say that most homes that burn in the wildland-urban interface ignite from embers,1 making a hardened home especially important.

Firefighters fighting a wildfire burning a homeHardening homes in the wildland-urban interface can help prevent the spread of wildfires.

A new study emphasizes the value of using ignition-resistant building materials, showing they can significantly reduce the chances a home or other building will be destroyed by a wildfire.

The study looked at the damage caused by the Camp Fire, which in 2018 destroyed almost 19,000 buildings in and around Paradise, CA, a small town about 90 miles north of Sacramento. Almost 10,000 single-family homes were destroyed and 465 damaged.2 In 2008, California strengthened its building codes to require ignition-resistant building materials for new construction in fire-prone areas, including Paradise.3

For single-family homes, the ignition-resistant building materials made a striking difference: 79.0% of homes built before 2008 were destroyed or suffered major damage compared to 40.6% of homes built in 2008 or later. Indeed, slightly more than half (50.6%) of homes built in 2008 or later had no damage, whereas only 17.7% of homes built before 2008 escaped damage.4

For mobile homes, however, ignition-resistant building materials didn’t reduce damage risk, possibly because the homes are so close together.5 We’ll talk more about that below.

The Wildland-Urban Interface: Wildfire Risk at Your Doorstep

What parts of a home can be made ignition resistant?

Homes can be made with a variety of materials, all of which fall into one of three categories: combustible, ignition-resistant and noncombustible.

The definitions of these terms are set by standards groups who conduct tests that simulate the conditions the material would be subject to in its use. For example, siding could be repeatedly wet, dried and exposed to ultraviolet light to simulate outdoor weather conditions.6

Examples of each material type include:

  • Combustible: solid wood, wood-based composite materials and plastic or plastic-composite materials.
  • Ignition-resistant: lumber treated with fire-retardant chemical and rated — based on standards’ groups testing — for outdoor use.
  • Non-combustible: metal (excluding aluminum) and traditional three-coat stucco.7

Ignition-resistant or non-combustible materials are available for many parts of a home, including the roof, gutters, siding, decking and fencing.

Other building materials can further protect homes:

  • Multi-pane, tempered-glass windows resist breaking even in high radiant heat conditions, keeping embers out.
  • Attic, roof and foundation vents designed to screen out embers reduce the risk of a spot fire.8 

A couple surveys homes burned by a wildfireHardened homes are less likely to be destroyed by a wildfire.

Embers, Wind and Fire: A Dangerous Mix

Find out more about ignition-resistant and non-combustible building materials from this guide from the Insurance Institute for Business and Home Safety (IBHS). If you have customers in California, the IBHS has a PDF with additional, detailed information they can use to build or retrofit their home for wildfire-resistance.
Remember, to effectively protect a home from wildfire damage, residents must regularly maintain these materials and, when needed, replace them.

Creating and maintaining space around your home

The study described above looked only at building codes and the building materials those codes required, which explains just one aspect of why some homes survived the Camp Fire and others did not. Two other major factors influencing the chances a home will survive a wildfire are the maintenance of the home and the area surrounding it.

Consider a home built with ignition-resistant materials but covered with combustible materials, such as dried leaves, or with combustible landscaping around the home. Embers landing on such a home have a greater chance of starting a spot fire than embers landing on a home without them.

Similarly, flames and radiant heat are less likely to reach a home with properly maintained space around it. The maintained space around the home is sometimes called defensible space. A better way to think of this space would be as the home ignition zone. The National Fire Protection Association (NFPA)’s zone system makes this concept easy to understand.

  • The Immediate Zone, which is most vulnerable to embers. This zone covers the area within five feet of the home’s furthest attached exterior point. Nothing combustible should be in this zone, meaning no propane tanks, firewood, flammable plants, furniture, needles in gutters, landscaping bark or anything similar.
  • The Intermediate Zone, which covers between five and 30 feet from the home’s furthest attached exterior point. In this area, landscaping should be carefully designed and maintained to reduce fire spread.
  • The Extended Zone, covering from 30 feet out to 200 feet, where landscaping should be designed to interrupt fire’s path and keep any flames that do occur small and on the ground.

Find specific details in NFPA’s guide to preparing homes for wildfire.

How the Growing Wildland-Urban Interface Increases Property Risk

The importance of community action

To effectively protect any home in a wildfire-prone community, homeowners have to work together to protect all the homes. Consider this scenario: a fire-prone area where there is only a moderate amount of space between homes, meaning each home’s Intermediate Zone overlaps with its neighbor’s. The homeowners must work with each other to create and maintain their zones.

This scenario is fairly common throughout Washington state. Just a few examples: Leavenworth, Cashmere, Soap Lake, Prosser, Wenatchee and Roslyn have all seen wildfire nearby and all include developed areas with homes in close proximity to each other. The mobile homes in Paradise almost certainly had overlapping Intermediate Zones.

The NFPA’s Firewise USA program helps community members take action together to protect their homes from wildfire risk.

The role of effective building codes

The California building codes implemented in 2008 set specific requirements about which type of material can be used to build certain parts of a home in fire-prone areas. Siding, for example, must be non-combustible or ignition-resistant. If it’s made of combustible material, the product must pass a fire-resistance test.9

Here in Washington state, Kittitas County already has fire-resistance requirements for new construction, and the state is working on strengthening building codes that local governments must adopt to improve fire resistance.10

In our next blog post, we’ll cover the major role humans play in igniting wildfires.

[1] Smithsonian Magazine: https://www.smithsonianmag.com/science-nature/untangling-physics-firenadoes-drifting-embers-other-wildfire-phenomena-180971735/

[2] Wikipedia, https://en.wikipedia.org/wiki/Camp_Fire_(2018) 

[3] Sacramento Bee, https://www.sacbee.com/news/california/fires/article227665284.html 

[4] Sacramento Bee, https://www.sacbee.com/news/california/fires/article227665284.html 

[5] Sacramento Bee, https://www.sacbee.com/news/california/fires/article227665284.html 

[6] Insurance Institute for Business & Home Safety, https://disastersafety.org/wp-content/uploads/2019/03/Wildfire-Retrofit-Guide-California_IBHS.pdf (PDF)

[7] Insurance Institute for Business & Home Safety, https://disastersafety.org/wp-content/uploads/2019/03/Wildfire-Retrofit-Guide-California_IBHS.pdf (PDF)

[8] Insurance Institute for Business & Home Safety, https://disastersafety.org/wp-content/uploads/2019/03/Wildfire-Retrofit-Guide-California_IBHS.pdf (PDF)

[9] Insurance Institute for Business & Home Safety, https://disastersafety.org/wp-content/uploads/2019/03/Wildfire-Retrofit-Guide-California_IBHS.pdf (PDF)

[10] Seattle Times, https://www.seattletimes.com/seattle-news/urban-wildfire-when-homes-are-the-fuel-for-a-runaway-blaze-how-do-you-rebuild-a-safer-community/ 

Robert Ferrell, P.E. is WSRB’s Vice President of Public Protection. He leads the team that manages the insurance rating of cities, fire districts and building departments throughout Washington state. He has more than 25 years of experience in fire insurance rating.

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