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NJ apartment fire

e hilton

e hilton

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Virginia
A large apartment complex, still under construction, burned this week in Somerville NJ. Following is a comment from “officials”. I like that term ... like “authorities” ... vague and official sounding. Anyway, what kind of lightweight materials are they talking about?

The fire started in the cockloft, or attic space, and spread so fast that by the time firefighters arrived, it was too late. Officials say the small, lightweight wood materials used to construct the building, especially in the attic, fueled the fire.

“That does tend to burn faster than solid, dimensional lumber,” said Somerville Fire Marshal Robert Lynn.

Lynn says those lightweight materials are up to code but are still dangerous, especially for fire crews.
 
When I've heard the term "lightweight construction" it's always been referring to 2x4s so in the case of an attic space it would probably be trusses. I have always thought of 2x4s as dimensional lumber also but...
 
The fire service uses the term "lightweight " construction to refer to wood truss or wood and metal constructed trusses, I joist.

Tradition ar legacy construction is used for 2x6 or larger rafters, joist both floor and ceiling.
 
Construction is often the most dangerous time for wood-frame buildings, because there are large undivided spaces, fire separations are not completed, uncovered framing is exposed, and sprinklers might be piped but the system isn't activated. All it takes is one cigarette in a trash chute.

I doubt that a stick-framed roof (2 bys) would hold up under a fire much more than a few minutes longer than trusses. You have to go to heavy timber (4 by or larger) for wood to hold up for any significant time in a fire.

I have long advocated for attics to be sprinklered, or at least have heat detectors, in multifamily housing. Draftstops are often torn up (it takes at least a 12" hole to run a data cable or TV coax), and there's a lot of kindling wood with the high-pitched roofs that are in style now. We have had several fires here in Richmond where a fire started outside, got through the eave vents, and raced through the attic destroying the whole building. Amazingly the residents got out before the flaming attic collapsed into the living spaces.
 
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We sprinkle attics in our city, after we lost part of a building, do to an outside fire
 
The other worry about the engineered trusses is that when the plates are exposed to heat, they start popping off the lumber. This could result in a structural failure before the fire structurally compromises the roof.

Ultimately, if it is not steel or concrete, the fire service does not like it.
 
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