Working Safely Around Wooden Trusses

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Trusses have been used in the building industry for over 100 years. Some of the largest Type IV mill buildings constructed during the late 19th century utilize trusses in their roof construction. They contain large wooden framing members with iron turnbuckles and iron nuts and bolts.

After World War II, when the returning GIs all wanted their piece of the American Dream, lumber suppliers could not maintain the level of support. As a method for survival the building industry invested heavily in "lightweight" truss use for roofs. Over the next 50 years, this use expanded to the use of trusses for roofs, floors and other building components and subcomponents.

One of our earliest wake-up calls came with the 1988 Hackensack, NJ, incident in which three firefighters perished in a car dealership. Another six were killed with the infamous "rain-roof" incident at a supermarket in New York City. The problem is this: even with this awareness, firefighters continue to be killed in buildings with trusses.

Is it possible to change the outcomes at incidents where trusses have been used? The answer is yes - but! We can operate at these incidents, but we need to change our culture and approach when buildings are confirmed to contain truss construction parts.

The first hurdle to overcome is our culture. We pride ourselves on being aggressive. This is how we are able to save the lives of civilians. Do we need to compromise safety to accomplish this feat?

As I wrote in the March 2002 issue, two words are found in far too many after-action reports of firefighter fatalities. They are "routine" and "size-up."

We are failing miserably in performing size-up. Too often, we are not giving germane information or the information is incomplete. We are too concerned with the textbook version of size-up with its 10, 12, 13, etc. important points. The critical aspect of size-up is that it imparts a picture to all arriving units, especially the responding incident commander, without taking up too much radio time. This can be accomplished by the following:

  1. Height/configuration
  2. Dimension (given in feet width first)
  3. Use of structure
  4. Scope of problem observed ("Fire from four windows on the number two floor of a four-story building")
  5. Special issues (extending vertically or horizontally, people trapped, etc.)

Did you notice that there is no mention of building construction type? The reason: there doesn't need to be one at this point and too often we don't know the type unless we have been inside or we go inside.

Builders today can reproduce any exterior you choose, so it becomes a moot point trying to guess the type. But size-up needs to be done effectively in both the front and rear of the structure. And a company needs to venture inside the structure if it is safe to do so and relay the type of construction back to the incident commander.

If trusses are involved, then another set of decisions need to be assessed by all on the fireground. This is where culture gets us into trouble, if you can remember back in time to fires in buildings where you had time to react and also to screw up. Unfortunately and also too often tragically, those times are gone.

After size-up, the next and perhaps most important point to consider is why do you have to go in. If rescue is truly needed and conditions are deteriorating, then minimize the number of personnel who go in, but protect them. This isn't intended to mean they have a hoseline with them. This means that if trusses are involved, a complete and accurate evaluation must be made before the crew goes in. The failure/collapse can and will occur without adequate warning.

The decision to go must be tempered by what is happening to the trusses. Is the fire affecting the roof or floors? Are the conditions tenable to support life?

This is and always should have been the terrible paradox where firefighters enter a structure subject to failure to save lives. We have not done as well with this as we should have. In my opinion, vacant structures do not fit this matrix. Commercial structures also can be left out. We cannot just go into these structures as kamikazes. If you don't know for certain that a building has been trussed, then you have to slow down and perform reconnaissance.

Trusses can and will fail in a variety of ways and degrees. Some common attributes do exist, however. All wooden trusses carry engineered loads at their absolute maximum capability. All wooden trusses will contain a metal gusset plate on the top and bottom chord exactly in the center of the truss. The failure of the gusset plates will lead to the failure before the wood will burn through. The most stable area around trusses is as close to bearing support walls as possible.

The collapses will be pancake, V-shape, lean-to or a sequence consisting of all three. The net result will be the same. If you are on top of the truss, you will ride it down, perhaps into the flaming inferno. If you are under the truss, you will experience the combined effects of the truss failure and additional byproducts of fire and smoke. In either scenario you will probably be killed.

Only if the need for rescues can be substantiated should fire personnel enter the structure. By substantiating the reason I imply that valid information is received that the occupants are still inside or the responders see the victims in the windows. Entry should be made cautiously and certainly with the thought that bailout may become necessary and bailout points have been established. Rapid intervention crews must be on scene and prepared for immediate deployment. The entry crews must stay as close to bearing walls as possible and limit the exposure time to danger. This is not a situation for young, inexperienced personnel. It also is not for the "cowboys" because they don't think, they just strap on and go.

To the aggressive firefighters who read this and dismiss it as not being the "true" way of firefighting and not in keeping with traditions, remember this before you kill yourself or worse cause someone else to be killed. This isn't your father's fire service anymore. These buildings are great against gravity, but add fire and its byproducts and they will fail.

To me, the politicians don't care, the end users don't care, even the victims don't care if we are killed in buildings with trusses that fail due to fire. We kill too many firefighters year after year in buildings with trusses, too often without live rescues being made, to continue this suicidal paradigm. Think about it and Stay Safe.


Michael L. Smith, a Firehouse® contributing editor, is a 29-year veteran of the District of Columbia Fire Department, currently deputy chief/suppression and shift division commander, commanding all fire, EMS, hazmat, special operations and special events activities in the District on shift. He is a 30-plus-year fire service veteran and is a graduate of the Executive Fire Officers Program at the National Fire Academy. Smith is a Certified Municipal Manger (CMM) from George Washington University; has degrees in fire science, construction management and labor law; and he holds a journeyman's card with United Brotherhood of Carpenters and Joiners.

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