Fences (and walls) have been around since ancient times. They are functional, provide privacy, and keep cities, businesses and homes secure. However, during a wildfire, a fence may do more harm than good.
Fencing comes in a variety of materials, but when it comes to wildfire, the wooden type is of primary concern. Much like vegetation, this flammable material can create a hazard when adjacent or connected to a home. Wooden fences and gates can also be a problem for fire crews trying to enter a homeowner’s yard during an event. Additionally, newer homes often are constructed close together with ‘zero lot lines.’ In this scenario, when flying embers are present, it makes it difficult and dangerous for fire crews to access a home, especially if the fence is already engulfed.1
Wood fences, because of their small vertical openings, can create an excellent source of fuel and ignition, given fire behavior and the right conditions. Wood fencing and attached lattice can be a concern as they tend to be thinner wood construction, which could lead to easier ignition and faster burning. Oftentimes they are also adjacent on ground level to flammable debris such as leaf litter or wood mulch, which can be easily ignited during a firestorm.
In an investigation by the University of Maryland of the 2007 Witch Creek and Guejito fires, 45% of the homes with attached wood fences were destroyed! Wood fences can be rapid conduits or “wicks” for a wildfire and can spread fire to attached or adjacent structures quickly. When fencing burns, it can spread up the wall of the structure onto the underside of the eaves, resulting in ignition of the roof assembly or soffit. In addition, fences can produce spot fires from their own ember generation.2
Strategies for fire prevention if using wood fencing:
- Use metal gates and/or heavy gauge wooden sections and include a noncombustible transition wall between the wood fencing and structure
- Keep fence clear of debris and not in or touching soil.
- Do not store combustible materials such as firewood against fencing.
- Avoid small gaps between boards because firebrands (also known as embers) are easily trapped there and can ignite the fence.
- Use wood that has been treated to be fire resistant pre-construction.
Finally, be aware of building codes for new construction in your jurisdiction as they may mandate fire resistive materials for fencing and these vary by state and city.
Jim Muttera is a Senior Risk Services Consultant with Chubb Personal Risk Services.