How To Build a Fire-Safe Dwelling
Hard lessons from tragic wind and firestorms.
• • • • • • • January 22, 2025 • • • • • • •
The home designed by Greg Chasen was spared—while neighboring homes were reduced to ashes.
The public misunderstands why fires are becoming more common and devastating in California. The common belief is that homes are too close to woodlands, where fires catch on easily. However, one home in Pacific Palisades contradicts that notion. Besides attributing luck to the surviving home, an architect, Greg Chasen, explains how design, with fire in mind, can help save neighborhoods.
To start, the architect designed the fire-safe building with a concrete wall around the property’s perimeter. Also, the home had a sparse Mediterranean-style landscape without plants around it. California Gold Fines, pebbles, or rock chips were used instead of a lawn, allowing playing and walking in the yard, but without the fire hazard: other factors — no eaves or overhangs preventing embers from being trapped in eddies. Chasen avoided Roof vents to prevent embers from entering the house. Of course, the roof was metal, with a fire retardant underlayment. It was designed without numerous roof intersections, minimizing the danger of embers catching and increasing the likelihood of fire.
Fortunately, San Francisco has more humidity in the air than Los Angeles. It is especially true when the Santa Ana Winds blow warm, dry air from the desert through Los Angeles County. San Francisco also has easterly winds, but they have a different name —Diablo Winds. Fortunately, the coastal influence here is strong.”
Some of the design features are not noticeable, i.e., the house walls have a one-hour fire rating. If there is a deck, it should be just as resistant to fire as steel or concrete, with a Class A wood rating. Glass windows must be tempered and with triple glazing to protect the interior of the house from heat. Also, stucco as a building material is fire resistant.
CLIMATE DIFFERENCES BETWEEN LA AND SF
Fortunately, San Francisco has more humidity in the air than Los Angeles. It is especially true when the Santa Ana Winds blow warm, dry air from the desert through Los Angeles County. San Francisco also has easterly winds, but they have a different name —Diablo Winds. Fortunately, the coastal influence here is strong. Wind typically moves from west to east, passing cold air filled with moisture over San Francisco. The air rushes to replace air rising from the heat generated by Oakland and other eastern cities, including Pleasanton, Pleasant Hill, and Concord. No doubt, air rising from the Sacramento Valley can also draw cold moist air from west to east.
There are several locations believed to be vulnerable to fire in San Francisco, one of them is the Crocker Amazon district. Other locations that are moderately vulnerable to fire are indicated in “green” on the accompanying map.
ZOMBIE FIRES
The Palisades Fire, Oakland Firestorm, and numerous fires in Canada that last through the winter while covered with snow are considered “zombie fires.” Zombie fires reignite under favorable conditions even though they are considered under control. The Palisades fire was spotted by firefighters and put out previously. Unfortunately, 6 days later, the fire reignited in high, dry Santa Ana Winds. The same is true of the catastrophic Oakland firestorm of 1991. The Oakland firestorm was reignited by 65 mph Diablo Winds after it was thought to be over. Diablo Winds, like Santa Ana Winds, occur in Southern California. They come from the east and are low in humidity, providing excellent conditions for fire.
Zombie fires in Canada are a little different. First, the fires smolder where peat moss is growing. Later, the fires reignite again when the snow has melted and conditions are dry enough. For example, at a time of year when fires are not burning elsewhere, British Columbia recorded up to 106 active fires in January of 2024.
Controlling zombie fires needs to be paramount in controlling catastrophic fires.
FIRE SUPPRESSION FOR DECADES
No doubt, the fire hazards initiated by European settlers for decades contribute to the catastrophic fires we have today. Despite the attempts to return to “controlled burning,” an indigenous fire practice that began 20,000 years ago, too often, the fuel loads are too high to contain controlled fires. When fuel loads are too great, mechanical means of removing vegetation is the only option. That is very costly and may explain why so few of our woodlands are safe.
Smokey the Bear warned, “Only You Can Prevent Forest Fires!” Unfortunately, when this ad was popular, fires were extinguished immediately, resulting in the dangerous fuel loads in our forest today. The good news? The US Forest Service has a better strategy today.
Glenn Rogers, RLA,
President, Coalition for San Francisco Neighborhoods (CSFN)
January 22, 2025
