UC Berkeley News


Steps you can take to protect your home during wildfire season
There's a lot you can do, the experts say, besides worry

| 31 October 2007

The state of California is adopting new building and fire codes, effective January 2008, that will primarily affect new construction. But homeowners with existing homes to worry about can take independent action to safeguard their dwellings in the event of a wildfire - an eventuality that is, or ought to be, top-of-mind for those who own or live in housing vulnerable to such a catastrophe.

Homeowners can increase the chances that their houses will be left standing after a wildfire with the right information, some advance planning, and regular maintenance, says Steve Quarles, wood-durability adviser for UC Cooperative Extension and an affiliate of the Center for Fire Research and Outreach at Berkeley's Richmond Field Station.

Quarles has identified six priority areas for making changes to existing homes in fire-hazard zones. He suggests homeowners start with the roof, the most vulnerable part of the house in a fire, and then continue in order with vents, vegetation, windows, decking, and siding.

First things first: Roofs and vents

Ignition-resistant "Class A" and non-combustible roofs - such as concrete tile and asphalt composition shingles - have become the norm in California since the late 1990s, when new laws passed requiring all new homes and all roof replacements in very high fire-hazard-severity zones to be Class A. Nevertheless, many older homes still do not have Class A roofs.

"The importance of the roof covering cannot be overstated," says Quarles. "If you haven't already done so, you should make an upgrade to a Class A roof your first priority."

The East Bay's hills are covered with flammable plants, as those who survived the 1991 firestorm (above) discovered. (Jonathan King photo)

But don't stop there. Many homeowners realize a false sense of security after installing non-combustible roofs and siding simply because those are dominant features on any house. There's much more to do, says Quarles, who specifies vents as the second item on his priority list.

Most building codes specify vents for crawl or attics to prevent a buildup of moisture, which can lead to mold growth and decay. But vents also offer embers and flames an easy entry point. "Embers that slip through attic vents can ignite debris and items stored there, and subsequently construction materials, setting the home ablaze from within," Quarles points out.

In addition, most codes require that vents be covered with, at a minimum, quarter-inch mesh to minimize plugging and reduction in air movement. But that's inadequate to keep flames away from the inside of your home, says Quarles. "This is an example of conflict in code preferences between building and fire officials. Quarter-inch mesh cannot stop embers and flames during wildfires. Smaller-mesh screens would do a better job of keeping them out, but they plug up more easily."

The importance of vents in wildfire resistance is leading to such innovations as the development of vents specially designed to limit ember intrusion while still allowing sufficient air flow for ventilation, and construction designs and procedures that permit unvented attics to avoid moisture-related problems.

Quarles suggests homeowners frequently check their vents to make sure there is no buildup of debris, such as highly combustible dry leaves and pine needles. For added protection they can make vent covers out of plywood or another solid material that can be quickly installed over vents when wildfire approaches.

Leggy and succulent

Next, suggests Quarles, examine the vegetation on your site, with the understanding that it can be both harmful and helpful when it comes to home fire protection. Plants close to the home - under eaves, in inside corners, and near windows - can be major fire hazards, but trees and shrubs farther away can serve as buffers against radiation, convective heat, and flying embers. "Trees might have a bad reputation because of the potential to spread fire in the crown, but that is seldom a hazard to structures," Quarles says.

In addition to noting where plants are located, Quarles suggests careful attention be paid to plants' innate fire resistance. Bushy junipers and cedars, for example, can be a poor choice for those seeking to minimize fire hazards. For landscaping close to a dwelling, select leggy plants with succulent leaves - the smaller the plants the better, especially near windows and in the parts of the home designed to give the house architectural interest, such as inside corners, where heat builds up much faster than on open, flat sides.

Whatever plants you choose, they should always be well-maintained, says Quarles: "Any plants near a house should be pruned, regularly watered, and kept free of dead material within the branches and on the ground."

Well-tempered windows

The next priority should be windows. Research has shown that by far the most important factor in determining the vulnerability of windows in a wildfire is the glass, not the frame.

"It's a good idea to install dual-pane windows with tempered glass," Quarles says. "With dual-pane windows, the outer pane protects the inner pane. The inner pane heats up more slowly and uniformly, and therefore may not break even though the outer pane does."

Tempered glass is much stronger than regular glass, so it provides more protection against breaking. The relevant chapter in the building code going into effect in 2008 requires at least one pane to be tempered glass. Since the type of frame doesn't make much difference in a fire, it can be selected based on cost, aesthetics, energy efficiency, or other factors.

As is the case with vents, homeowners can fabricate window covers out of half-inch plywood or another fire-resistant material. Cut them to size and mark them clearly so they can be installed quickly over windows before evacuating the home when a fire breaks out.

A backyard deck is not a top-of-mind hazard for many in wildfire country, even though an ignited deck is often adjacent to large windows or sliding glass doors, both of which can break from a fire's heat, permitting flames to enter the house.

"In general, the thicker the deck boards the better," advises Quarles. "Boards an inch or less thick release heat much faster, and are therefore a higher hazard. Be especially mindful of the gaps between the boards and the house and decking. Combustible debris can build up in the gaps and corners, and flying embers can get lodged there and begin smoldering."

For replacement, consider any material - plastic, plastic-composite lumber, fire-retardant-treated lumber for exterior use, or lumber - that passes the state test procedure approved by the California State Fire Marshal's office. Tests conducted a few years ago showed some composite-decking products capable of resisting fire as well as solid wood, though none were better; Quarles says he expects new decking products to come on the market when the 2008 building code goes into effect.

The sixth priority is siding. In research trials, good-quality sheathing - which is installed underneath the siding - was a key to protecting the home's studs. Non-combustible siding, made of stucco or fiber-cement, can be installed over the sheathing. Combustible siding - such as wood panels and clapboard - should be inspected annually for gaps, making sure that any are filled with a high-quality caulk to prevent hot embers from taking up residence and beginning to burn.

Even beyond these six priority areas, other elements and structures in and near your home (e.g., fences, garages, and gutters) can be improved to keep it safer in a fire. For further information, consult the "Homeowners Wildfire Mitigation Guide," co-written by Quarles and Frank Beall, a retired professor of environmental science, policy, and management at Berkeley, at groups.ucanr.org/HWMG/index.cfm. The UC Center for Fire Research and Outreach is online at firecenter.berkeley.edu; Quarles' page on that site (firecenter.berkeley.edu/quarles/squarles.htm) offers detailed PDF files with information (including testing results) about specific home features, such as roofs, walls, decks, and windows. Finally, an interactive website with information about actions to take before, during, and after fires is at www.wildfirezone.org.

[an error occurred while processing this directive]