Lightweight construction: Hazards you should know

Lightweight construction: Hazards you should know

By Jason Poremba, January 5, 2011

As the building industry evolves, it’s constantly developing ways to create building materials and methods that can allow construction to be done in the most efficient way possible. Building professionals and engineers are working to decrease the time involved in not only the production but the installation, too.

Cost is clearly the driving force in these decisions — and a physical example of this evolution has been the introduction of lightweight construction. It’s brought serious ramifications to the fire service and how we work on the fireground.

The NFPA states that, “Although these materials reduce construction costs and have consistently demonstrated equivalent or even superior quality under non-fire conditions, the same cannot be said when these materials are exposed to fire loading during a residential structure fire. The result is progressive structural collapse due to the failure of these lightweight structures, resulting in firefighter injuries and death.”

This article will highlight some of the dangers of lightweight construction, offer some size-up recommendations and provide some video examples of fire in such structures. First, check out the following video from the South Carolina Fire Academy of a burn demonstration of framing types:

Over the past few years, you may have noticed an increase in reports of firefighter close calls and fatalities related to lightweight construction, which has hopefully created better awareness of the issue within the fire service. It has forced departments to evolve further to differentiate between conventional framing and those using lightweight pre-engineered materials.

The introduction of lightweight construction materials should have changed the way you operate on the fireground. A series of tests done by the UL offered some glaring results. The failure time of a non protected 2×10 framing member was 18 minutes and 30 seconds after ignition time, and the equivalent member in a “TJI” failed in 6 minutes and 30 seconds.

But the goal of this article is not to overwhelm you with scientific facts, codes and potential resolutions. The real point here is creating awareness; if you have not altered your approach and attack on these types of fires, you need to adjust immediately.

This following video, from STATter911, focuses on two house fires minutes apart on July 2, 2007, in the Leesburg, Virginia area. One was older construction. The other was made from newer lightweight materials. Loudoun County Fire Marshall Keith Brower talks about the lessons learned from comparing the two fires.

How can you protect you and your fellow firefighters? It is fairly easy. Firefighters need to develop a culture of continual and evolving size-up. We have heard it a million times; “Size-up starts when the tones go out.” But for me, size-up starts when you wake up in the morning. Size-up will also need to evolve over time to allow for changes in the fire industry, the construction industry, and changes in your own response area.

Size-up for today is only as good as today. We need to educate our firefighters to be able to rapidly identify various types of construction, and the methods and materials utilized. Consider developing a system to notify responding firefighters of potential construction hazards.

Certain communities have already developed a hazmat-like placard system that allows responding firefighters to determine the type of construction upon arrival. The signage design and location would be in a predetermined location enforced by the local building and code officials; here’s an example from New York.

Collapse can often be catastrophic in lightweight construction compromised by fire. This video is from a house fire on Summer Creek Rd in Oconomowoc, Wis., in October last year: 

Firefighters should be trained in not only the construction types and methods, but also to understand the differences in fire behavior as a result of different construction methods. Building construction will determine the number of firefighters, apparatus and equipment needed to control fire, proper location of attack and vent, and whether the attack should be an offensive or defensive one.

Leadership must clearly understand fire progression and constantly assess the time the fire has been involved. There may be certain fires that may be an exterior attack on arrival just as a result of the amount of time the run was dispatched and the amount of time it took to respond.

The fire from the exterior may be visually “attackable,” but the floor structure may not allow for an interior attack. Six minutes is a very small window to operate under. Use a defensive strategy whenever trusses have been compromised or exposed to fire, and remember basic risk reward concepts.

Conduct search and suppression drills that emphasize tool use. Firefighters must continually move with a tool to feel ahead of themselves. Using a tool will allow the firefighter to sound out the floor to get a sense of structural integrity. The tool can also be used to sweep ahead of them to feel for already collapsed or compromised areas of flooring.

In 2000, the Phoenix Fire Department and the National Institute for Standards and Technology (NIST) conducted live burn tests on four residential structures to determine how long after ignition a structural roof collapse would occur. Check out the following video:

NIOSH provides the following recommendations to firefighters based on previous fatality-related incidents:

  • Use extreme caution when operating on or under truss systems.
  • Notify the incident commander whenever truss construction is discovered.
  • Communicate interior conditions to the incident commander as soon as possible and provide regular updates.
  • Use a defensive fire-fighting strategy once burning of truss members is identified (unless someone is trapped).
  • Expect imminent collapse once lightweight truss roofs or floors are involved in a fire (Klaene and Sanders 2000).
  • If possible, avoid cutting the truss chords when cutting holes for roof ventilation. Cuts can weaken the roof.
  • Avoid roof areas loaded by air conditioning units, air handlers, and other heavy objects.
  • Be aware of alternative exit routes at all times when working above or below a truss.
  • Consider using roof ladders or working from aerial ladders or platforms instead of walking or standing directly on the roof (Brannigan 1999; Dunn 1998). 

Filed Under: Anatomy of BuildingsEngineered Systems & Materials


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