Building to protect your home against wildfires-case history

From Pacific Polymers website-a case study on preventing your home from burning, read and implement the building methods suggested.

Use only one hour fire rated deck coatings

ONLY ONE HOME SURVIVES DEVASTATING FIRE STORM
Studying the houses that survived the 1993 Laguna Beach fire storm yields lessons in building to withstand the heat
by John Underwood


Fire-Resistant Details

Imagine this: A brushfire, blistering and intense, breaks out on a dry, windy day and races up hills and down valleys, devouring trees, cars and houses. By the next morning the flames are gone, and the heavy clouds of black smoke have washed away to sea, leaving a clear view of charred trees and hundreds of seared foundations. Yet somehow, a few houses still stand, vivid against the backdrop of ruin.

That was the scene in October 1993 after a fire storm destroyed nearly 400 homes in Laguna Beach, California. The fires started several miles inland and swept to the sea at a brisk 2 mph to 4 mph, consuming increasingly thick vegetation along the way. Often, the course of the blaze forced the firefighters to make stands at what they considered to be the least defensible positions: the doorsteps of homes. Frequently, the flames boiled 50 ft. or 60 ft. into the air, and they reached temperatures of 2,000°F or greater. When the fire became that intense, the firefighters then were forced to abandon the structures, which in some instances burned to the ground in five minutes.

Now, more than a year and a half later, rebuilding efforts have begun to reclaim the blackened California hills and bare mountaintops where many houses once stood and where only a few houses remain.The most obvious question homeowners, builders, architects and code officials asked as they combed the rubble for clues was how did a precious few structures survive such an inferno while houses on all sides vanished in the fire? What they learned was a number of lessons that likely will work their way into local building codes and should help to reduce the damage of future fires.

Houses burn from inside out

At 400°F, curtains, wallpaper and bedding ignite. Wood studs spontaneously combust, or pyrolize, at about 450°F (steel studs melt and deform at only slightly higher temperatures). At that point, single-pane windows blow out from heat and ambient-pressure differences. Flame and heat rush in to meet interior combustion, thoroughly consuming structures. Whole houses can reach temperatures hot enough to weaken and spall concrete foundations. According to Laguna Beach Fire Chief Rich DuBerry, many if not most of the Laguna homes lost to fire burned from inside out.

Extreme heat -- with or without direct flame -- compromised the envelopes of houses and ignited material inside by entering houses through vents; poorly sealed doors or windows; and cracks in walls, subfloors or attics.

When such heat is present, destruction is a matter of time. The critical question is how much time is there? Any structures exposed to extreme temperatures and flame long enough will burn. For DuBerry Laguna's lessons are clear: "Keeping the envelope sealed can buy precious time."

Why did some survive in the midst of charred destruction?

The home of To Bui and Doris Bender was called a "miracle house" by the Los Angeles Times because of its dramatic survival in a neighborhood almost totally devastated by the fire. Why did this trilevel structure and a few others like it survive while neighbors' homes on all sides, sometimes no more than 10 ft. or 15 ft. away, burned to the ground?

Cement coatings protect the wooden structure

"It's in the details," Bui insists. He knows about such details. Originally from Vietnam, he lived and worked as a structural engineer in Germany for more than 10 years. There, the predominant building materials are concrete, stone, brick and steel. "In Germany, structures are designed to last hundreds of years," he said. "I built my house to last." He insists his Laguna home is not overbuilt. "It's just that whatever the minimum codes called for, I went a little further."

For example, exterior walls are 2x6 wood-frame construction, which allowed Bui to install R-19 foil-faced insulation (the code requires R-11, kraft-faced insulation). Exterior-wall stucco was as much as an inch thick (nominal thickness is 7/8 in.). Ordinarily, nominal thickness of stucco is 3/4 in.

Eliminate the eave overhang

To prevent heat buildup, this house was constructed without eave overhangs, which also eliminates soffit vents. Cornices are built up with 2x12s and 2x8s and covered with 1-in. stucco. The class-A fire-retardant roof tiles are plugged with metal bird stop. Where 1/2-in. wallboard is the minimal requirement on interior walls and ceilings, Bui opted for 5/8-in. wallboard and one-hour-rated exterior doors and jambs.

Where single-pane windows are acceptable in this mild climate, Bui installed dual-pane windows by International Window Corporation (310-928-6411; www.intlwindow.com) that contain an insulating air gap.

Roofs on the prevailing ranch-style or cottage-style homes in the area typically had 2-ft. or 3-ft. overhangs and undereave vents that trapped heat and flame and induced ignition. Bui eliminated eave overhangs altogether in his design and replaced them with double 2x fascia, which he then stuccoed over.

Ventilation, ordinarily found in soffits, on the ridges of roofs and in crawlspaces, was placed at the midpeak points of gable-end walls. Bui positioned horizontal, eyebrow-type roof vents on the class-A cement-tile roof at every peak, which allows the quick and efficient release of attic heat. That is a critical factor because attic insulation ignites at about 450°F. There are no crawlspace vents in Bui's house.

Minimal gable-end vents and dormer-type roof vents are adequate to ventilate the roof of this Pacific Coast house. Soffit vents are eliminated altogether. The reduced venting meets code for the area because of the greater concerns for fire safety. Behind the vents, 1/4-in. wire mesh was installed to cut the risk that cinders would be drawn into the attic space.

Bui covered wood-deck surfaces with successive layers of a fire-resistant polyurethane and a sand-coating product manufactured by Pacific Polymers Inc. This is a three-part, trowel-applied material that cures to about a 50-mil thickness and carries a Los Angeles Fire Department class-A fire rating. Bui installed scuppered drains before he applied the coating to allow drainage at several points through the subfloor.

Extra layers of protection: Eliminate exposed wood


Wooden deck surfaces are troweled over with several layers of fire-resistant coating. Undersides of all decking are stuccoed over with a 1-in. layer of cement. The glassed-in deck rails are further protection against fire.


The owner of this Laguna Beach house stuccoed the undersides of all wooden deck surfaces to a maximum thickness of about 1 in., virtually eliminating any exposed wood.

Bui stuccoed the undersides of all exposed decking to the same thickness as exterior walls (photo above). The result is a house with virtually no exposed exterior wood.

Every house around Bui and Bender's house burned. But when firefighters broke into the house to search for occupants, the place was a "cool" 100°F, Bender said.

Photo courtesy of FINE HOMEBUILDING - HOUSES