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Just an interesting fact I learned last night. I was watching the news and the fire department did some research on how stable the roofs are on todays new homes. With todays building standards being used, they lit a house on fire, climbed up on the roof (with a cable attached to a harness) and stood there untill they fell through. Now, aside from the fact that I probably would have put a similar weight object or even a crash test dummy up there insted of a person with a bad adrenelin addiction, it took only twelve minutes for the roof to colapse and the structure to become fully enveloped. I was curious how it would go anywhere else due to the weight of tile roofs, or any other factors we do differently here. The test was done to look at the discontinued use of O.S.B. and how significant the truss spacing standards are in conjunction with O.S.B. and tile, etc., etc,.
Just a Friday morning thought.
CSR in AZ
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The bigger take-home message I've gotten from my firefighter cousins is that whenever they get to a fully involved house, there was a defect in the drywall - unrated lighting fixture, attic access left open, unfinished remodel, drywall removed and not replaced. If a continuous drywall covers the walls, then the fire stays in one room for a long time.
For the roof to collapse in 12 minutes, they must have removed drywall or started the fire in the attic.
Oh yeah. Remember to wear safety harnesses when walking on top of burning houses.
*my take is similar to dave's... something missing if it was 12 minutes...in a house i build... the only way the roof is going to get involved is if the windows get blown out or in .. and the roof will vent thru the soffit..other than that.. the last thing left will be uncharred wood next to the cellulose insulation...
*WBA At Your ServiceWe did a fire job about 6 or 7 years ago where the homeowner of about 2 months, went through her 5 year old development home and put 100 watt bulbs in all of the recessed fixtures. One of the high temp cutoff switches failed in a fixture buried in the attic ceiling insulation (fiberglass). The attic was wide open with no drywall covering (as most are). I think we replaced 65 rafters and 70% of the roof sheathing. The homeowners were home and lucky the fire occurred during the daytime and that the firemen were close by. I have worked on many modern home fires like this. The drywall only protects you within the envelope.
*I just reroofed a house built in the late 60's, early 70's. A brady-bunch plan! The sheathing was 3/8th ply. All the houses waved at ya! Told the homeowner if the firemen ever show up, tell them to ley it burn, or work it from the truck! Took a few days to get use to! No permit was needed for the reroof, and no money left in the budget, so it was a "don't ask, don't tell" situation. I guess good enough if it lasted this long, but.....Jeff
*Tim is right on. We run a surprising number of fires that start in the attic. Out here in the central San Jaquin Valley, shake roofs and spaced sheathing (1x4's 8"-10" O/C) are pretty routine. Once an attic fire gets ripping it pretty much takes the whole roof, so falling through is not a problem: the roof is already vented when we arrive. The problem we see is roof collapse due to failure of the gang-nail plates. They heat up, deform and fall out. Then the roof structure fails, usually right under the roof mounted HVAC unit.
*And steel framing still doesn't make sense?Yes, typically you will find plywood/OSB sheathing and decking a steel framed house. But consider the likelihood of a fire to start in a house framed with steel? It does not fuel a fire. True, it has a heat failure point like any product. But it is so rare that it lends itself to a consuming fire that it's insignificant.It's a bear to work with, and it generally ends up being more expensive to build with, but I feel much better about the homes I'm putting my customers in. Today's dimensional lumber... as much as I like working with it... stinks.
*Mr. Therrien,Steel framing does make sense.The Machine
*I do some work with steel, and never found it to be as bad as it reputation. But, fire wise, steel bends, wood chars. A wood beam will retain most of it's strength, the outer char becomes an insulator, while a steel beam will bend, twist and deflect.....ultimately failing where a wood beam would have held. Both wood and steel will fail with a good air source to feed the fire. Worry more about fireblocking, and full drywall jobs than wood vs steel. Jeff
*If you can stand on any roof that I frame for twelve minutes, I consider you a hero. And there doesn't have to be a fire burning either.blue
*b WBA At Your Serviceblue you been boogerin' near my house ? I think I saw some of your work on Friday.
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Just an interesting fact I learned last night. I was watching the news and the fire department did some research on how stable the roofs are on todays new homes. With todays building standards being used, they lit a house on fire, climbed up on the roof (with a cable attached to a harness) and stood there untill they fell through. Now, aside from the fact that I probably would have put a similar weight object or even a crash test dummy up there insted of a person with a bad adrenelin addiction, it took only twelve minutes for the roof to colapse and the structure to become fully enveloped. I was curious how it would go anywhere else due to the weight of tile roofs, or any other factors we do differently here. The test was done to look at the discontinued use of O.S.B. and how significant the truss spacing standards are in conjunction with O.S.B. and tile, etc., etc,.
Just a Friday morning thought.
CSR in AZ