Wood Truss test Burn

This video was created to help show firefighters the dangers of wood truss roof assemblies when they are exposed to fire. The video contains excerpts of tests burns that were conducted on a wood truss assembly and also a wood "stick built" roof assembly. The test burns were not scientific and are not intended to discredit trusses; they were conducted simply to help educate the fire service of the dangers that trusses pose if they are exposed to fire. Trusses have many good features. The issue the fire service needs to be keenly aware of is that they fail quickly when exposed to a fire. Granted most building codes provide a good degree of protection for trusses. But the problem arises when the fire either originates in the truss space or, somehow, extends into it, thus exposing the truss to fire. And then, as Francis Brannigan so accurately stated, "Gravity Always Wins"

Category:

Howto & Style

Tags:

• Wood
• Truss
• test
• burn

[brianps73]

You stated that your trusses were attached using nails. Were you referring to the trusses being attached to the walls or the actual construction of the trusses? To my knowledge trusses are held together using gusset plates or gang nails. These are the weakest part of any truss section and in a fire will almost always fail first.

Traditional stick built homes are of course going to last longer due to amount of nails used to hold the roof framework together as well as the additional supports nee

[dkwalsh]

@brianps73

Brian,

The truss roof was made using "regular" wood trusses with metal gusset plates. The plywood was attached using screws. For the stick built roof assembly, we used nails to connect the wood members together and screws to hold the plywood on to the wood members.

Not a highly scientific test but fairly convincing; seeing is beliveing.

Thanks for watching and the feedback-DKW

[wprd227]

good video but on the second one the frame stayed standing for 21 minutes but when did the plywood fall thats when it really failed not when the frame fell cause once the plywood fell all the weight went with it correct so at that point it lasted for however long after the plywood with out weight. im not disgradeing the video its a great video im just pointing out a minor detail that should be looked at also

[dkwalsh]

You're correct, the sheathing failed first and the weights fell through before the "stick built" structural members failed. This was just a "down and dirty" simple "experiment". If we get to do it again undoubtedly we'll adjust or methods-thanks for the comment!

[rosscorion12]

It would be cool to see another view... maybe a top view (roof view) to see what it looks like right before the truss fails. Two firemen (plus gear) would weigh about 500lb., so it would fail even faster than 5 minutes if someone was up there venting...

[dkwalsh]

We had a few firefighters posted up on a near-by training structure watching,they said they saw no indication of an impending collapse; it was literally there one second and gone the next. You're 100% correct; we only put 300 lbs spread out over the roof whereas 2 firefighters in full PPE with proper equipment can easily weigh more than 250 lbs.each. There's a message here....Thanks for watching, commenting and realIzing the potential dangers; NEVER TRUST A TRUSS!!!DKW

[Himdarling44]

Also another good rule, if you are worried about the roof collapsing with somebody on the roof, you shouldn't have guys under it either.

[Himdarling44]

This is an interesting test but it does little to prove anything not already known. Sure trusses will fail faster, however with open air like that they fail even faster because they fire is already vented and builds faster than if it was a closed in attic space. Both roofs will fail eventually. What is more important is determining, based on fire conditions, to put your guys on a roof at all. Your fire conditions should dictate your roof tactics, construction should be just a side note.

[brianps73]

My entire comment didn't post. I was going on to say that your demonstration though not a high dollar one was effective. Any cadet who viewed this would have learned the difference between the two types of construction and how they react to fire. Some people are just too quick to degrade the hard work others do instead of seeing the positives that can come from it.

I'll always remember this " never trust a truss, they fail fast in fire!"

Stay low and stay alive.

Firefighter

Houston,Tx.

[datzfast]

thank you, this is a fair test comparison.

now, please educate people that it is the contents that burn a house down, and empty house is hard to burn down as any arsonist will tell you.

[dkwalsh]

That is just what it was made for- to help educate firefighters. In 1998-2003 alone 29 firefighters died as a result of truss failures in a fire.