Posted By dayle1 on 16 Jul 2013 03:03 PM

2x6 stud walls. While I did have soffit vents, they were parallel to the wind direction and the wind was so strong that heat damage to the tree leaves was limited to the lower 10ft. Fire spread mainly occurred on the lee side of objects where embers came to rest. Most trees had enough moisture and bark that they did not burn, just blackened on the lee side. But any dry wood on the lee side of a building and it was gone. We even had a stand alone covered patio, one 4x4 post burned completely and a few feet of the 2x6 roof truss, nothing else, structure left standing on 7 remaining posts.

A wood framed home is much more difficult to make fire resistant than a concrete or steel home. With wood you have a much lower fire rating than with concrete. Wood needs to be vented so attic vents, soffits, ridge vents, wall vents, etc., are installed but these make for ember paths to enter the structure and start a fire.

Roof trusses are notorious for failing due to fire. Firefighters really despise them because when they fail, the entire structure goes. The problem is the density of the wood. They use young growth lumber that does not do well when exposed to flames and heat.

California now has a defensible space of 100 feet in effect in some counties. The old 40 feet and 60 feet has been changed to 100 feet.

Where was the home located at?

Today in the Arizona Republic the investigations into the Yarnell Fire has shown that defensible space saved homes.

AZ Republic Article


Per the Article:(emphasis mine)

"Almost all the buildings in the burn zone that had been adequately cleared of surrounding brush survived the Yarnell Hill Fire, according to the first known study of the deadly blaze. However, only 63 structures out of 569 in the community, or 11 percent, were properly defended, according to researchers at the Pacific Biodiversity Institute. Of the 63, 60 were safe, while the fate of the other three could not be verified by the Washington state-based conservation-research group, which used satellite imagery and mapping software in its study."

This speaks volumes on defensible space. Of the 63 structures that had defensible space, 60 of them survived, or a 96% survival rate of the structures due to defensible space.

 

As per the article:

"The study concluded that Yarnell and Glen Ilah “were not prepared for wildfire,” like the Yarnell blaze, which claimed the lives of 19 Granite Mountain Hotshot firefighters and destroyed at least 115 structures."

Here is a similar picture (except it has a yard I'd actually enjoy):

If the two pics posted are indicative of the 63 houses with their definition of defensible space, then it is clear why only 11% of the homes in the area meet that definition. Neither zoning codes nor individual incomes support that amount of defensible space for the majority of us. Also, much of the terrain immediately around Yarnell is rocky with limited vegetation, but also limited building sites. In the first picture, that is Foothills Drive in the background with houses on more residential size lots and as the pic shows all of them and the trees along Foothills Drive did not burn. Defensible also requires resources and there will never be enough resources to defend all structures. My house had defensible space, it was less than a mile of our wildfire's ignition point and it survived the initial fire wall before any fire resources arrived. But when resources were available, they were assigned to more defensible, read higher value, properties. So, if you have higher than average defensible space and higher than average property value and there are sufficient resources, you may be fortunate. Otherwise, just keep your insurance up to date.

Posted By dayle1 on 21 Jul 2013 08:53 PM
If the two pics posted are indicative of the 63 houses with their definition of defensible space, then it is clear why only 11% of the homes in the area meet that definition.

The picture posted by JonR is NOT related to the Yarnell Hill Fire. I don't where that picture was taken but it is NOT from the Yarnell Hill Fire.

Here is some footage of the current California wildfires. Pay close attention to the homes burning; NONE of them have defensible space, the fire is not even near some of the homes and the roofs are completely ablaze (embers landing in attic and soffit vents), and all wood construction.

California Wildfire

Gotta disagree that avoiding high fire risk areas would rule out construction in the West. There aren't too many forest fires in Colorado Springs proper, but plenty of handwringing about people building on acreage in the surrounding mountainsides. We tolerate boneheaded lifestyle choices that generate sales and profits.And I mean bonehead. On the Jersey shore, homeowners sued to stop construction of berms that could have kept Sandy at bay. They didn't buy oceanfront property to look at sand dunes. Nosiree.

Personal responsibility. We have known how to build houses just about everywhere for some time. I live next to a river and take my chances.