The science.
Wood Shingle or Wood Shake Roof Fires, page 1, paragraph 4, NFPA Fire Analysis and Research, Quincy MA (NFPA is National Fire Protection Agency --- they develop the fire codes that protect you).
"An average of 4,200 fires starting with exterior roof coverings, surfaces or finishes made of sawn wood occurred per year during the five year period from 1994 through 1998. These fires caused an average of five civilian deaths, 23 civilian injuries and an estimated $7.0 million in direct property damage per year. During this time period, these fires accounted for 0.7% of the 567,100 total reported structure fires, 0.1% of the 3,744 civilian structure fire deaths, 0.1% of the 21,293 civilian structure fire injuries, and 1.1% of the $7.2 billion in direct property damage."
What this means:
(4,200) / (567,100) = .0074 = .7%
About one half of one percent of fires start on wood roofs.
5 / (567,100) = .000009
One person dies in a fire starting on a wood roof at approximately one in a hundred thousand fires.
(3,744 - 5) / 5 = 748
Conclusion: You are seven hundred forty eight times more likely to die in a fire that starts somewhere other than the roof.
The biggest problem is in the house.
"An average of 4,200 fires starting with exterior roof coverings, surfaces or finishes made of sawn wood occurred per year during the five year period from 1994 through 1998. These fires caused an average of five civilian deaths, 23 civilian injuries and an estimated $7.0 million in direct property damage per year. During this time period, these fires accounted for 0.7% of the 567,100 total reported structure fires, 0.1% of the 3,744 civilian structure fire deaths, 0.1% of the 21,293 civilian structure fire injuries, and 1.1% of the $7.2 billion in direct property damage."
What this means:
(4,200) / (567,100) = .0074 = .7%
About one half of one percent of fires start on wood roofs.
5 / (567,100) = .000009
One person dies in a fire starting on a wood roof at approximately one in a hundred thousand fires.
(3,744 - 5) / 5 = 748
Conclusion: You are seven hundred forty eight times more likely to die in a fire that starts somewhere other than the roof.
The biggest problem is in the house.
In addition, new wood shake roofing materials in California (and maybe your state) are required to be pressure-treated with a fire retardant. The retardant is certified by Underwriters Laboratories to last the life of the roofing material (50 years in the case of heavy shake):
University of Texas says you are 30 degrees cooler under wood shake.
Let's ask ourselves an honest question. What is a cool roof? Well, if I were to ask you a common sense question, what might you say? Let's find out. Let's pretend it's a hot day, say around 100 degrees. Let's pretend you are barefoot. Now, you have three choices of surfaces to walk on, all of which are out in the sun: a street, a sidewalk, or a wood deck. Which one would you choose? A wood deck? That's what a wood shake roof is made of. How about that sidewalk? That's what a cement roof is made of. The street? That's asphalt, the same type of material as the asphalt composition roofing. See, you already knew what was right. So, most of the home power bill concerns heating or air conditioning. The wood shake roof helps with air conditioning by keeping the surface cooler, plus it is a roof with open sheathing --- meaning, it's all a vent. Do the other roofs help with heating? Well, you heat during the winter. In winter, the sun is low and not much of a factor for heating. The winter is when you need your best attic insulation. So, there you have it. You knew before I told you. Here's the science:
What about earthquakes?
When your home moves, it would be nice if the roof would move with it. However, some construction methods place very heavy loads on the roof, such as cement tiles. (The next time you are in a big box hardware store, try lifting a bag of cement). Loads have inertia, sort of like trying to push a bus off the road instead of a small car. It's not going to move. So, when the ground moves, the roof stays put. This can rip apart the structure between the ground and the roof. With wood shake, a very light, strong roofing material, the roof moves with the structure, as shown below. This is a home in the Northridge earthquake, where many tile roofs collapsed:
