David A. Greene

Published Writing - Summer 2008

Building Construction

Modern building construction presents us with many challenges. For instance, lightweight steel truss roofs, which are prevalent in commercial construction, are quick to fail. Some references indicate failure may occur in as little as ten minutes of fire exposure. In fact, a large department out west has a policy that any fire identified using thermal imaging cameras in the ceiling area of a building with lightweight steel truss design triggers a building evacuation and a tactical shift to defensive operations. With this in mind, we should all feel warm and fuzzy when we pull up to the 40 year old building that was built back when they really built buildings, right? Unfortunately sometimes, nothing could be further from the truth. Let’s examine one such case. 

It’s a sunny pre-spring afternoon with light variable winds and we have been dispatched to a grass fire in a relatively rural area. Given it’s our tenth grass fire of the shift, we pay it little significance. While only half-way to the scene, dispatch upgrades our call to a structure fire and dispatches a full structural alarm assignment. Now our adrenaline may be moving a little. We arrive to find a 100 ft. x 60 ft. building used as a restaurant with pressurized black smoke showing from the Charlie side at the roof level. Command is established, a walk around is performed, 5” is laid from the hydrant across the street, the only hydrant within a mile of the building, firefighters don personal protective equipment, RIT is established, a single 1.75” hose is advanced inside. Interior crews quickly find the fire and report a good “knock” on it. Outside, the IC sees smoke change to light gray/white and is no longer pressurized, but still easing out of the roof level on the Charlie side. Interior crews begin overhaul but report that they are unable to access the void spaces above the ceiling due to construction. Examination reveals that a plaster in wire mesh drop ceiling sits below a wooden tongue and groove ceiling and the interior crews call for power tools to try to gain access. After fifteen to twenty more minutes, the IC reports continued smoke from the roof level on the Charlie side. An aerial truck is put into service and crews enter the roof. They report light smoke easing from the top of wall Charlie. They report the roof covering is composite rubber matting that is heat sealed with tar. They begin to try to access the void spaces from the roof. K12 saw cuts are made and reveal asphalt shingles over a wood deck under the composite roof covering.  Additional cuts reveal that under the asphalt shingles with wood deck is a steel truss.  

Just so we keep the score straight, our building has a tar and rubber matting roof, which covers asphalt shingles, which covers a wooden deck, which covers a steel truss, which covers a wooden tongue and groove ceiling which covers a plaster in wire mesh ceiling.  

Roof crews report no fire directly underneath the cuts they’ve made and interior crews report only light smoke drifting inside and visibility at 50 feet. Now we’re over ninety minutes into the incident and everyone is becoming frustrated at not being able to find the fire. But as in all fires, if you don’t find it, it will find you. In a matter of just a few minutes, the IC sees a definitive shift in smoke production back to dark gray and black pressurized smoke. He orders the roof crew to evacuate the roof. This task must be done so quickly that some equipment is lost during the evacuation. Fire is now showing from the roof and with no way to fight it from inside, the interior crews are evacuated. A quick PAR check matches accountability tags to firefighters and exterior operations commence which brings with it a second and third alarm. Two aerial trucks with master streams are applied to the building along with assorted large caliber hand lines and a fourth alarm is requested to assist with manpower and establish a tanker/tender shuttle in order to augment the single accessible pressurized hydrant. 

So, there we are. We are two hours from having a good knock on the fire and now the roof is collapsing, the building is three-quarters involved and the IC is already painting lines for what will be the proverbial parking lot at the conclusion of this incident. The four alarms have brought nearly 100 people and 25 apparatus to the scene.  

What went wrong? Well, the answer is simple. Nothing. Anytime you have a building that is older than ten or fifteen years, you should insure that if the owner/occupant has changed roof types that they haven’t simply added a roof type. Any changes or additions should be clearly documented on your pre-fire survey. In our scenario, our 60 year old building started with a wooden roof with tongue and groove ceiling and asphalt shingles but it began to disintegrate. Several years later a steel truss roof was added but it over time began to rust. Another wooden roof was placed on top of the steel truss roof and as it became worn the built up tar and rubber matting was added most likely to seal leaks.  At some point the dry wall in wire mesh ceiling was added for appearance to the inside.  New additions to our building created multiple void spaces. Interior wall breaches occurred allowing for new structural supports and lateral fire spread. All of this occurred in a building originally constructed 30 years before any building codes were enforced.

It is paramount to note also that in our scenario building, the fire originated on the Charlie side near the center of the building but the roof failed first on the Delta side near the Delta/Alpha corner. This is the area farthest from the ignition and is the newest of the seven additions. Moreover, we should look at the wall construction. Large, tall exterior load bearing walls may support the roof construction but may also be dependent on the roof construction to be held upright. This means shortly after the roof collapses, we can bet a paycheck that one or more of the now unsupported walls will collapse. This should be recognized early in the incident in order to appropriately place exterior streams that are above or outside of the collapse zone. 

As firefighters, driver/operators, incident commanders, etc. we must always be concerned with construction type, and in particular roof considerations. There are plenty of concerns in modern construction such as bowstring and lightweight steel trusses, gusset plates that are only stapled, pressed or glue in lieu of gusset plates. However, we must not forget that older construction doesn’t always signify better construction. A 60 year old building originally constructed from the Art Deco design movement of curved construction and rounded ends and is updated to modern construction with ninety-degree angles will always present you with void spaces. Think of putting a rubber ball inside a cardboard box. There will be void spaces. We cannot change the type of construction or roof that we are given at each incident, but we can and must insure that we have the knowledge ahead of time, through our pre-incident surveys, to make a calculated risk-benefit analysis on those incidents. Remember, too, that hard nosed firefighters don’t ever like to lose, regardless of the cause. In a case such as our scenario building, it is essential to maintain accountability and prevent those hard nosed firefighters from being missed in the confusion. If they were attempting a last stand in the interior, even in the area farthest from the fire, they can still be trapped in a collapse. As we saw in our scenario fire, the roof farthest from the fire failed first. Again, accountability is essential on any incident but particularly when transitioning from offensive to defensive operations. Insuring that everyone is on the same page (incident action plan) will help to efficiently extinguish the fire without any unnecessary injuries. 

Be safe and do good.