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Building in the Time of Wildfires

Author: Nina Olivier, Built Green Coordinator

Between extreme heat and drought across the entire Western U.S. the annual wildfire season has arrived early in the Pacific Northwest. Climatologists warn that as climate change progresses this trend will continue into the future with increased likelihood of longer and drier wildfire seasons.

During the construction phase of any project, there are strategies that can be implemented to keep the build site and staff safe and healthy during wildfire season.

Builder with protective mask

Worker Safety

Naturally, outdoor workers – including those who respond to wildfires – are most impacted, both directly (from the fires themselves) and indirectly (from smoke and fine, airborne particles dispersed by the fires). The Washington State Department of Labor and Industries has approved an emergency rule to protect workers from wildfire smoke.

When it comes to protecting workers on job sites from hazards caused by wildfires, there are several strategies employers can implement.

Preventing Damage During Construction

With the expansion of the Urban Growth Areas and residential construction into previously undeveloped forests and wildlands, build sites are increasingly at risk from wildfires. Known as wildland-urban interface areas (WUI), these areas are where houses are in, or near highly flammable wildland vegetation.

There are fire prevention construction strategies builders can prioritize in WUIs to prevent starting a wildfire and ensuring the safety of their project and staff from risks associated with wildfires.

  • Prepare a hazard and risk assessment to determine the wildfire fuels, weather, topography, assets at risk, and the wildfire occurrence.
  • Create a defensible space that acts as an area around a home in which vegetation, debris, and other type of combustible fuels have been treated, cleared, or reduced.
  • Ensure access roads and driveways are wide and strong enough to accommodate emergency vehicles and provide access for necessary firefighting efforts.
  • Strictly enforcing no smoking policies
  • Restrict the use of space heaters in high-risk areas
  • Properly training workers on safe work practices and fire prevention
  • Storing combustible materials away from buildings that are under construction
  • Placing fire extinguishers at individual work areas and ensuring workers know how to operate them
  • Avoid starting vehicles and heavy equipment on top of dry vegetation

Building with metal shingle roof, stucco walls and plastic windows

Building Design

Addressing the impacts of wildfires and the smoke they produce in Built Green projects during the design phase, rather than at the end, will go a long way in providing better indoor air quality, protection and resiliency from house fires, and higher value for buyers.

In fact, many insurance companies offer discounts and rebates to clients with fire-safety features that have been pre-built and installed into the building further increasing the home’s value.

  • Select a development site that considers topographic features such as slopes, canyons, local vegetation, and weather that influence wildfire behavior.
  • Keep garages detached from the main home as they are often ignition sites that can impact the main housing unit.
  • Exterior Walls:
    • Use siding materials that are noncombustible or fire-resistant and not susceptible to melting are recommended such as three-coat stucco, shale, metal, and fiber cement siding. A minimum fire-resistance rating of 1 hour for the wall assembly is recommended.
    • Use structural insulated panels (SIPs) or Insulated Concrete Forms (ICFs) that have superior fire suppression properties to conventional stick frame construction.
  • Roof:
    • Install Class A rated roof assemblies with noncombustible coverings using metal, slate, tile or clay.
    • Install eaves with short overhangs and flat soffits with a minimum of a 1-hour fire resistance rating.
    • Install leaf guards over gutters to prevent leaf debris from collecting in the primary ignition zone.
  • Vents that are a minimum of 10 feet from property lines and other buildings, constructed of metal products, and have corrosive-resistant metal mesh screens are recommended.
  • Windows and all other glazing should be fire rated or triple-pane with at least one layer of tempered glass.
  • Avoid materials containing PVC or Vinyl that produce toxic fumes when they melt or burn that are dangerous to residents and firefighters.
  • Decks:
    • If building a wooden deck use exterior grade fire-retardant-treated wood lumber, do not use Ipe/Ironwood or any other endangered tropical wood species. Add metal sheathing around the base timbers.
    • If using a composite decking material specify a Class A or B fire rating, but avoid composites that contain PVC, which produce very toxic fumes when they burn.
    • Install metal screening around the crawlspace beneath the deck to keep fire embers out.
    • Increase the defensible space of the home by building a stone, paver, or concrete patio, instead of a deck.
  • Fences and walls constructed of noncombustible materials such as concrete, stone, and masonry are recommended. Attaching a fence or wall to the building should be avoided unless the fence or wall is constructed of noncombustible materials.
ICF Wall from ICF Homes of Virginia
Defensible space zones from ReadyForWildfire.org

For more information visit FEMA’s website.

Diagrams produced by ICF Homes of Virginia and ReadyForWildfire.org

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