Hardening Homes and Structures Against Wildfire
There are steps you can take that can make a home and other structures around your property more fire-safe and therefore, potentially much more survivable during a wildfire.
Burning embers, also called firebrands, are the principle cause of ignition and loss of structures during wildfires. In fact, studies have shown that 80% of homes lost in wildfires due to firebrands landing on or near the structures ahead of the fire-front, not from the main fire itself. Embers can result in ignition directly on a structure, or indirectly by igniting combustible vegetation or materials on or near your home that would result either flames touching your house or a radiant heat exposure that may break a window and ignite items in the interior.
Areas of concern on structures are:
- Roof and roof edges
- Exterior walls and attachments thereto
- Surroundings where combustible materials and vegetation are near the structures
The survival of your home, garage and other buildings and structures will depend on:
- Improvements you make to these structures themselves, both in terms of materials and design
- How well your home is maintained
- Residual fuels that are on your property
As a large mostly horizontal surface on which wind-blown firebrands can come to rest, roofs are the most vulnerable part of any structure. Combustible roofing materials and debris left on the roof represent a huge risk during a wildfire. So are gaps in roofing materials such as with tiles that allow firebrands to contact the combustible roofing underlayment and ignite it.
How well your roof performs during a wildfire depends upon:
- Roofing material, its fire rating and any gaps to the combustible underlayment
- Age and condition
- Complexity – levels, wall-to-roof intersections and where debris can collect
- Gutters, overhang and other edge-of-roof factors – Gutter screens should be used to prevent accumulation of combustible debris and overhangs kept in good condition
- Vents, skylights and other roof penetrations – Skylights made of two layers, one of glass will resist larger burning embers and vents of no great than 1/8” mesh can stop the small firebrands from entering the attic space and crawl space under the house. There are specialty paint products that can be applied to larger mesh vent screens that will swell the openings shut upon the heat from a fire.
- Walls are vulnerable at lap joints, if any. And besides burning into the interior framing, combustible siding can ignite the overhanging eves and gable-end vents, and ignite the interior through windows and doors. Fire on an attached deck can ignite these items as well.
- Eaves/overhangs with gaps to adjacent surfaces are places where firebrands can come to rest and ignite the structure. A boxed-in or soffited eave overhand is ideal.
- Windows that break during a wildfire will allow burning embers (firebrands) and flames to enter the home. Tempered dual-pane windows are best to resist fire and heat. Some inspect screens help, too. Window shutters or covers are even better protection. Plywood applied to the walls (before evacuation during a wildfire), covering the windows, can provide a greater level of protection, too.
- Decks, walkways, landings, porches and patios directly connected or very near the building, if made of combustible materials, can lead to fires as described above. Non-combustible materials such as light-weight concrete, tile or stone are usually ideal in terms of fire resistance. Elevated decks can be problematic in a couple of ways. Firstly, what is stored under them: Firewood, lumber or other flammable material should not be stored under elevated decks. Secondly, burning embers can enter the underside and potentially igniting the structure from below. Therefore, screening off the underside with plastic lattice panels covered with inspect screen can prevent firebrands lodging on the underside. Vegetation must be prevented from growing under the elevated decks, as well.
- Garages with ill-fitting roll-up or swing-up doors can allow firebrands entry and ignite the contents. Weather strip these doors to close open gaps. Comments about windows apply for garages, too. Prevent fires from entering your garage and other storage buildings.
- Firewood piles and gazebos or other structures located very near your home can be risky. Move these to at least 10 feet from structures. Consider fire resistant tarps to cover wood piles.
- Create Defensible Space, clearing flammable landscaping and weeds to at least 100 feet from each structure and building.
- Avoid using wood bark or shredded rubber for ground cover that touches or is close the building. These ground covers are flammable. Use non-flammable materials such as decorative rocks nearest to and up against the house.
- Use only fire resistant plants nearest the home and keep them pruned so they don’t provide a fire “ladder” to your windows, eves and roof. The links below provide recommendations on fire resistant plants, some that also are deer resistant and drought tolerant.
- Keep landscape well-watered, especially up against the house.
More information and ideas can be found at the University of California’s Homeowner’s Wildfire Mitigation Guide that include Quick Fixes, Long-term actions, Pre-fire readiness, Wood Decay and a great checklist of all the above recommendations.