Keeping Your Fence from Burning Your House Down
By Ronald Hodgson
You can easily reduce the chances your fence will ignite in a wildfire, prevent the spread of flames to your home or business, and avoid contributing to dangerous ember storms. Careful research by the Insurance Institute for Business and Home Safety has identified how wildfires ignite fences and how those fence fires can carry flames to your home or business. See also a fact sheet from the National Fire Protection Association.
Wooden fences catch fire easily in wildfires. Burning fences can carry fire to your house or business. When wooden fences burn, they generate a blizzard of hot embers that start fires downwind in the landscape and on buildings. And, of course, no one wants to lose an expensive privacy or security fence.
Embers, direct flame contact, and radiant heat all cause fences to ignite and burn. Ember storms are common in wildland urban interface fires. Embers lodge in cracks between boards and accumulate in little drifts in corners where posts, rails, and boards meet.
Embers also light dry grass, decorative mulch, and accumulated litter and leaves at the bottom of the fence. These small fires easily light the fence boards and flames spread quickly up the boards. Flames spread to neighboring boards, posts, and rails.
Avoid planting easily ignited plants such as junipers and rosemary next to the fence. Embers will ignite them, and they will ignite the fence. Don’t stack firewood or construction materials against the fence.
You can replace the wooden fence with non-flammable materials such as masonry or stucco. Using a nonflammable gate to separate the building from the fence usually prevents the fence fire from igniting the structure.
Alternatively, you can treat your fence each year with a retardant such as Flame Seal Wood Seal A. If your fence is made of cedar, you can use Flame Seal Shingle Seal; it protects for multiple years. This will completely stop ignition in most situations. If ignition occurs, flame spread and burning intensity will be greatly reduced reducing damage to the fence and the chance of carrying fire to the building.
You can paint the fence with a wildfire resistant paint such as Flame Seal 84 Wildfire. Painting the gate, posts, and the first fence panel out from the building is an alternative to using a metal gate. A wildfire resistant paint covered with a topcoat of exterior vinyl or latex paint will provide protection for many years.
Mowing and clearing away dry grass, leaf litter, and other debris; removing firewood and other flammables from near the fence; replacing easily ignited and highly flammable vegetation; and keeping the area around the base of the fence are effective ignition prevention measures. Alternatively, or in addition, wildfire retardant can be sprayed on dry grass, leaf litter and weeds for a distance of thee feet out from the fence. When flames or embers encounter the retardant, a carbon char forms that prevents ignition and stops fire spread.
Explore retardants in more detail on the Flame Seal Products and Wildfire Protection Services pages on this website. There, you will also find Do-It-Yourself instructions. Contractors who can apply the retardants and coatings and provide other landscape maintenance for wildfire protection are listed there as well.