[MrLonzo]

I lived in Southern California for over 40 years. My house, and most houses there are stucco over wood frame with Class A roofing shingles made of fiberglass/asphalt or clay.

Stucco is not a flammable material. It is composed of Portland cement and sand, neither of which are flammable. Class A roofing shingles are fire-resistant and can withstand exposure to direct flames without catching fire, according to numerous online sources. You’ll find inside most of these upscale houses lots of tiling, stainless steel, mirrors, glass, and other non-flammable materials.

So how do embers get to the wood frame leading to the burning down of the entire house? And how do the fires spread so quickly from house to house (one report says “length of a football field in 90 seconds”). Yes, wind is an accelerant, but fire needs flammable fuel.

I don’t disbelieve the pictures I’m seeing, just trying to understand how this happens.

[Bill14564]

Just a guess but wood trim, plastic soffits, and general attic ventilation would all contribute.

The fire rating of the shingles are no match for the temperatures of a wind-driven wildfire.

[OrangeBlossomBaby]

Originally Posted by MrLonzo

I lived in Southern California for over 40 years. My house, and most houses there are stucco over wood frame with Class A roofing shingles made of fiberglass/asphalt or clay.

Stucco is not a flammable material. It is composed of Portland cement and sand, neither of which are flammable. Class A roofing shingles are fire-resistant and can withstand exposure to direct flames without catching fire, according to numerous online sources. You’ll find inside most of these upscale houses lots of tiling, stainless steel, mirrors, glass, and other non-flammable materials.

So how do embers get to the wood frame leading to the burning down of the entire house? And how do the fires spread so quickly from house to house (one report says “length of a football field in 90 seconds”). Yes, wind is an accelerant, but fire needs flammable fuel.

I don’t disbelieve the pictures I’m seeing, just trying to understand how this happens.

A wildfire can get to temperatures reaching close to 1500°F. Glass can liquefy at 1400°. Class A shingles are designed to withstand temperatures under 700°.

Unless you live in a brick house with a brick foundation and a brick roof, with no windows at all, your house is likely to burn in a wildfire. And if you do live in that brick house, it will become the oven that consumes you.

[CarlR33]

I thought I saw the winds were 80-100 mph so we are talking about a hurricane type of blow torch coming down the street. The fire department is taking a beating but I am not sure how you can easily direct water from a fire hose with that kind of wind speed? Apparently it’s disastrous enough the insurance companies are pulling out (prior to theses fires) similar to Florida.

[Kenswing]

I fought wildland fires in the west for 20 years. There is very little that won’t burn given enough heat. With the winds they get in SoCal this time of year, if there’s any way for the fire to find a way in it will. It doesn’t even need to have flames hit. Just the amount of conductive and radiated heat will get things burning.

[Dusty_Star]

Originally Posted by Kenswing

I fought wildland fires in the west for 20 years. There is very little that won’t burn given enough heat. With the winds they get in SoCal this time of year, if there’s any way for the fire to find a way in it will. It doesn’t even need to have flames hit. Just the amount of conductive and radiated heat will get things burning.

& there's your answer. It explains a football field length in 90 seconds.

[Decadeofdave]

Embers flying though the air at 100 mph start the vegetation on fire around your house. Don't forget humidity is 8 percent.

[ElDiabloJoe]

I saw an article that referenced why the Getty mansion (and museum) in Malibu survived. It is not the same as the Getty Museum in the Sepulveda Pass area.

It survived because staff had maintained a rigorous schedule of trimming back vegetation, staff turned on all irrigation to wet/cool the surrounding vegetation, and they turned off / closed vents and A/C systems that suck in and spread hot air and embers.

Not saying it was fool proof, but centrally seemed to have worked wonders in this instance.

[62SkiDoo]

Mechanisms of Fire Spread

"When a fire starts, it can spread in four ways: conduction, convection, radiation, and direct flame contact. Understanding these mechanisms of fire spread is essential for enhancing fire safety and protection.
Conduction

Conduction is the transfer of heat through a material or between materials that are in contact. Materials such as metal, wood, and other solids conduct heat well. When a fire is in contact with a material, it can transfer heat to the material. The heat then spreads through the material, causing it to ignite and spread the fire further.
Convection

Convection is the transfer of heat through a fluid, such as gas or liquid. When a fire heats up the air around it, the hot air rises and cooler air rushes in to replace it. This creates a convection current that can spread the fire to other areas.
Radiation

Radiation is the transfer of heat through electromagnetic waves. When a fire burns, it emits heat in the form of radiation. This heat can travel through the air and ignite other materials that are not in direct contact with the fire.
Direct Flame Contact

Direct flame contact occurs when a fire comes into direct contact with a material and ignites it. Materials such as paper, wood, and other solids are highly flammable and can easily catch fire when exposed to flames.

Fire spread can also occur through heat transfer. Heat can ignite nearby materials, even if they are not in direct contact with the fire. Materials that are highly flammable, such as gas and liquid, can quickly spread a fire.

By understanding the mechanisms of fire spread, you can take steps to prevent fires from starting and spreading. Ensure that materials that are highly flammable are stored safely and away from potential ignition sources. Install fire alarms and sprinkler systems to detect and extinguish fires before they can spread."

[Bjeanj]

Just read this article this afternoon that addresses this very question.

California Fires: Why Some Houses Burn and Others Are Untouched in L.A.

[MrLonzo]

Interesting article. However, I’m still trying to imagine how the house ignites if windows and doors are closed. Let’s say one of those embers gets into a vent as the article suggests. If an ember were to get in a plumbing vent jutting up from the roof, for example, it would drop down through a copper pipe and likely be doused by the water in the p-trap. Plus, inside the pipe, there is no wind to stoke the ember.

Some of the houses in the photos have nothing left but ashes. Did the refrigerator melt?? Stainless steel has a melting point of 2500 deg. F. Clay bricks will crumble to ash at 2000 deg. F, yet many houses saw only the brick chimneys survive. It takes time to melt metal even at very high temps. So what is fueling the fire to make it hot enough long enough to melt metal and crumble the stucco walls?

[OrangeBlossomBaby]

First of all, you're not looking at nothing but ash. You're looking at ash covering whatever is under it. Probably those refrigerators you're wondering about, in various degrees of disrepair since any wooden flooring under the refrigerator, and the electric cords, and the door handles, and the feet, and the plastic inside of it, would have all burned and melted long before it was completely ensconced in ash.

Second, as I said in my previous response, shingle roofs CANNOT withstand the temperatures of wildfires, which can get up to almost 1500°F. California was experiencing hurricane-force winds of up to 100MPH, so basically it was a neighborhood-sized flying blowtorch, as someone else referenced upthread.

Doors aren't made of metal. Glass melts, air pressure shatters glass, and the flames just waltz right into the houses, burning them to a crisp. Garage doors are not made of stucco, and many stucco homes have wood frames. When you surround a home with 1400 degrees of fire, it will burn.

[rsmurano]

I also lived in California (Montecito Santa Barbara area) and our house was burned down with 230 others back in 1977 due to Santa Ana winds. 1977 Sycamore Fire - Santa Barbara Bucket Brigade
Back then we had cedar shingle roofs, Beauty brick, wood siding. We lived in a canyon and while packing up the van, fire jumped over the hill, over half a mile were the fire was burning and now it was directly on the other side of the road from us. Winds were almost 100mph. We left down the road and parked about a mile away. We had the same issue with no water pressure. We saw a fire truck try to hook up to a hydrant near us and got nothing so they kept going. My neighbor stayed with his house so I tried to walk back to the house in the dry creek along the road but the embers were flying all around me so I went back to the car.
According to my neighbor, the houses with storage sheds started burning and embers were landing on the cedar shingles and that’s all it took. My neighbor with little water pressure put as many sheets and bed covers in the bathtub to get them soaked and laid them on his roof and this saved his house. He was lucky.

We were in another 20,000 acre fire some 15 years later and had to be evacuated. This time, we all had asphalt shingles but with high winds, burning tree branches falling on the houses, and cedar wood siding, it didn’t take much to start the houses on fire.
Fires create an inferno and embers fly blocks if not miles from the existing fire to start new fires.

[MikeN]

With enough heat anything will burn

[Rzepecki]

Originally Posted by MrLonzo

I lived in Southern California for over 40 years. My house, and most houses there are stucco over wood frame with Class A roofing shingles made of fiberglass/asphalt or clay.

Stucco is not a flammable material. It is composed of Portland cement and sand, neither of which are flammable. Class A roofing shingles are fire-resistant and can withstand exposure to direct flames without catching fire, according to numerous online sources. You’ll find inside most of these upscale houses lots of tiling, stainless steel, mirrors, glass, and other non-flammable materials.

So how do embers get to the wood frame leading to the burning down of the entire house? And how do the fires spread so quickly from house to house (one report says “length of a football field in 90 seconds”). Yes, wind is an accelerant, but fire needs flammable fuel.

I don’t disbelieve the pictures I’m seeing, just trying to understand how this happens.

Thank you for asking these questions; I’ve learned a lot.