Many of us watched the massive wildfires in fall, 2003 and wondered, "what
can we do to protect our home from fire?" Since it is difficult to recreate
a wildfire in a lab, there has been little laboratory research on what changes
can be made to a house in order to eliminate any "weak points." However,
many veteran firefighters, and fire officials across
the United States have singled out changes that can be made to greatly increase your house's survival success
from an encroaching fire.
The problem with soffits and attic
Exposed soffits and eaves are potential heat traps and are at risk of catching
fire. But this problem isn't the only threat. Soffit vents, which are designed
to allow a roof to breath, also provide a freeway for flames and heat to enter
an attic. To minimize exposure, enclose all eaves and soffits with a mold resistant
gypsum underlayment. Cover it with fiber-cement sheathing. To vent attic spaces,
it's safer to use ridge or gable vents. Be sure all exposed vents and chimneys
are covered with 1/8-inch corrosion-resistant steel screens to keep out convection-driven
Siding - Enclose your house with firewalls
Exterior walls are vulnerable to both radiant and convective heat from a wildfire.
During an intense fire, vinyl and aluminum siding melts, exposing the wall's
vulnerable interior. A layer of 5/8-in gypsum sheathing under either vinyl or
aluminum siding can increase the level of protection significantly. However, non-combustible
and fire treated wood sidings are the preferred choice of materials.
Siding materials like cement stucco, stone, pressure treated cedar siding, or
other masonry materials are better choices if you live in a fire-hazard zone.
But stucco and other masonry assemblies are prone to cracking and need to be
maintained to be affective.
A good site plan is your
first defense against wildfire
Consider fire defenses as a series of concentric
spaces, or zones of managed landscape around your
home. These zones act as natural breaks that
can slow the spread of fire. Consult your
local forest-service agency (www.fs.fed.us)
for help with selecting plants that have natural
Long-term maintenance is also important. You should
eliminate "ladder fuels" - vegetation that provides
a path for fires to climb from the ground to the
treetops - by removing tree branches that are within
12 feet of the ground. To eliminate potential fuel
Also, you should store firewood and flammable fuels
at least 30 feet from the house. Any plants that
can dry up and burn easily should be kept away from
contact with the side of the house.
- remove dried vines from the
side of the house
- keep gutters clean
- sweep your roof of any build
- prune shrubs
- remove dead leaves
Noncombustible materials won't
make a house fireproof
a noncombustible material like metal roofing or
siding doesn't burn, metal is an excellent heat
conductor. During an intense fire, enough heat
can be conducted through the metal to ignite the
material behind it.
When grouped with noncombustible materials, fire-rated assemblies can provide
additional protection. A fire-rated assembly is a combination of materials
forming a component of a building, such as a roof or a wall, which resists
ignition while protecting the rest of the structure.
Fire rated assembly comes in a Class A- B- or
C-rating. The best form of a fire rated assembly
for a roofing material is a Class "A" assembly
that uses pressure-treated cedar shakes with a
fiberglass underlay. This arrangement adds an additional
protective barrier for the home.
The most vulnerable component
is the roof
American Society for Testing Materials (ASTM) has
a test to determine the hourly rating of an assembly.
It exposes an assembly to heat and flame on one side
and tests for heat transmission, burn-through, structural
integrity, the ability to withstand water pressure
from a fire hose, and the assembly's capability of
carrying its own load.
During a fire, wind-driven embers, which have been known to travel
as far as ½-mile from a wildfire, can stick to the rough surfaces or
valleys of a roof. If roof materials are flammable, the structure can catch
fire long before a wildfire arrives. To protect your home, consider using any
of the three classes of fire retardant pressure treated cedar roofing materials
It's recommended that if you are going to chose an assembly, choose the highest
level of protection for your home with a Class "A" rated roofing system
which uses a fiberglass underlay beneath the pressure treated shingles for optimal
A roof sprinkler system is, at best, a backup to a fire-resistant roof assembly
(See National Fire Sprinkler Association web site at www.nfsa.org). Although
a wet roof can reduce the chances of radiant and direct-flame combustion, roof
sprinkler systems aren't foolproof. Water pressure tends to be low during a fire,
and if sprinklers are pump driven, the electricity that powers the pump can fail.
Also, fire-generated winds can redirect the spray from the roof.
and skylights are vulnerable
Windows and skylights are weak points. That's because they can fail before a
building ignites, allowing fire to enter a house. (Which is why an interior
sprinkler system is a good idea). During a wildfire, single pane windows last
only a couple of minutes before they break. Thermo-pane and double-glazed
windows last twice as long.
During a fire, the window's sash causes a differential in the heating and stressing
of the glass, causing it to crack. On smaller windows (less that 2-feet wide),
cracked glass usually stays in place and continues to offer some protection.
On bigger windows, glass falls out because it's too heavy for the sash to hold.
Your best bet, especially on the windward side of the house, is to use non-combustible
shutters that latch to protect your windows. Another good practice is to use
low-e (low emissivity) tempered glass. The ultra-thin metallic coating on the
glass dramatically reduces the fire's radiant energy from entering the house
and possibly igniting drapes or other flammable material. Tempered glass, although
expensive, resists high heat that weakens most glass and resists impact from
Low-e tempered glass needs to stay in place. Vinyl frames warp, and then melt
until the window fails. All aluminum frames would seem like the best choice because
there are no combustible components; however, they melt at 1200 F. Pressure
impregnated wood sashes will hold the glass in place best.
If replacing your existing windows isn't an option, you can use full-cover metal
screens of noncombustible storm panels (www.shuttertime.com)
to protect windows from heat and flying embers. These galvanized-steel storm
panels aren't rated for fire but are used to protect windows from hurricane force
winds and blown debris.
Decks and fences are potential
An attached deck, trellis,
or fence should get the same attention as
a roof. A deck on a sloping hill is the ultimate
firetrap. Fast-moving ground forces can ignite
a deck, turning it into an unwanted barbeque.
If a wood deck is your choice, enclose you
perimeter below you deck with 1/8" metal
screening, fire retardant treated siding
or non-combustible siding. The screening
will stop burning embers and combustible
materials from blowing under the deck.
Choosing decking material is also an important. A recent study conducted by fire
marshals in Arizona showed that many of the new synthetic materials are
more prone to fire than traditional cedar or redwood decks. Although
more rigorous testing needs to be completed, you should choose these materials
After a wildfire rips through a forest, all that's left is the blackened tree
trunks rising from the scorched earth. The thick trunks don't turn to ash because
they have a low surface-to-mass ratio. They burn, but slowly, which is why heavy
timber decks are considered appropriate for medium to high-risk areas.
Typically, decks are made from 2x materials. While perfect for load bearing structures,
2x materials have a low surface to mass ratio and catch fire quickly. When building
a deck from wood, to give the maximum protection from fire,
large 6" or thicker beams should be used for structural supports and at
least 3" thick boards, with a pressure treated fire retardant, should be
used for decks.
What are the chances of surviving a large-scale wildfire?
Mills, from the Colorado Springs Fire Department
stated, "If you create a defensible space with
all your roof and exterior home elements, in an
extreme wildfire (which typically means mammoth
100 foot high flames, traveling at 100 miles per
hour), your home might have a 50% chance of survival".
In the British Columbia and California wildfires
of 2003, many homes simply imploded. This was due
to the massive temperature differentials from the
gigantic wall of flames that approached these houses.
Studies done after the 1990 Painted Cave Fire, which involved an analyses of
hundreds of aspects that may influence survivability, found that homes
threatened in the typical wildfire encroachment
with a fire-rated roof and exterior, and a vegetation
clearance of 10 meters or more had a 90%
survival rate, which increased to 99% when defensive
actions where also taken by civilians
On the flip side, it has been said,
a home with no defense elements had only a 20%
chance of surviving a wildfire. The majority of
homes in the US are built in areas that are considered
low-risk to wild fires. In these areas statistics
show that less than 1% of home fires originate
on roofs of any type. 98% of homes burn due to
ignitions from inside the house.
Why do some districts choose to ban wood roofs?
it is a lack of informed decision-making that contributes
to a politician's or building official's ruling to
ban wood in any given area. The majority of the time
officials don't even understand that Class-A wood
roof is considered equal in the level of fire protection offered
as other non-combustible roofing materials rated
by organizations such as UL. ICBO, UBC, NFPA, and
In a majority of the cases, when building officials
are not influenced to make quick rulings, due to
such large scale disasters such as the California
fire of 2003, and research is conducted into the
various different fire rated roofing materials available
on the market and the qualifications they hold, wood
roofing is always an option used in those
district's building codes.
Areas such as:
information on ways that your state can protect against
- Pueblo, Douglas County, Co.
- Jefferson County (above 6400
feet), Co. Class "A"
- Park County, Co. Class "A"
- Castle Rock, Co. Class "A"
- Boulder City, Co. Class "A"
- Boulder County , Co. Class "C"
- The entire state of California
has requirements from Class "A", "B" and "C"
- Chaparral Pines Subdivision,
Arizona Class "A"
- And many other districts around
the United States
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2004 | Disclaimer |
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