Geoscience Reference
In-Depth Information
nite interior curtains, rugs, etc. Double-pane windows and heavily insulated walls
will slow the rate of heat penetration into interior spaces.
• The only buildings to survive the Laguna Fire had insulated walls, double-pane win-
dows, and blocked or minimized venting. A well-insulated, well-sealed building en-
velope, and high thermal mass, will slow interior heating and ignition.
• Minimize venting, and screen all vent openings to prevent flaming embers from en-
tering vents. Removable fire-wall vent blocks should be placed in front of foundation
and roof vents during periods of extreme fire danger to keep hot air from easily pen-
etrating the building envelope.
• One of the few Laguna homes in the path of the firestorm to survive had a 40-foot-
wide strip of the green succulent “ice plant” (creating an excellent “defensible
space”) and a concrete tiled roof (an exceptionally fire resistant roof). The firestorm
blew right over the top of the ice plant and the house, dropped burning embers on the
concrete tile roof, roasted a 10-foot-wide swath of ice plant, but failed to ignite the
building's structure.
• Stucco, cement, or earthen walls are preferred. If wood siding is desired, it should be
applied over a 5/8-inch sheetrock fire wall for improved fire resistance. Cement-
based weather board can look like wood but give you cement board's superior fire
resistance. Even with a stucco or cement weather-board sheath, an underlying wood-
framed wall might ignite if the firestorm gets hot enough.
• All projections (roof eaves, etc.) should be protected on the underside with cement
stucco or cement board (like Certainteed or Hardie Board) that looks like wood. A
less-preferred alternative is to paint natural wood with fire-resistant coating to im-
prove its resistance to ignition by burning embers. Hot air rises and can easily ignite
roof overhangs in a firestorm.
• Coat wood decks with multiple layers of a fire-resistant urethane deck covering (Pa-
cific Polymers or similar) or treat wood decking with fire-resistant coatings (Fire
Stop or similar).
Note:
Chemical treatments, such as Fire Stop, will inhibit ignition
by burning embers, but will not prevent ignition due to a superhot firestorm. A stucco
coat (¾ inch or thicker) on the underside of wooden decks was credited with saving
two homes in the Laguna Beach fire. There is a new fly-ash composite decking board
from LifeTime Lumber that has a “Class A” fireproof rating, and is LEED certified
for its recycled content, that can be used to build high-quality fireproof decks. Trex
and many of the other similar competing composite decking manufacturers have
come out with “Class B” fire-resistant wood/plastic composite decking to meet Cali-
fornia's new wildland fire codes.