Different Tactics Called for with 'Throw Away Homes'

Jan. 9, 2009
Firefighters are no longer working in structures that were built to last, like those buildings where you could simply scrape away the charring and move back in.

Firefighters are no longer working in structures that were built to last, like those buildings where you could simply scrape away the charring and move back in.

Many should recall in the late Francis L. Brannigan's writings that the factory buildings of earlier days were specifically constructed to sustain a fire without loss of structural integrity. Often there could be a fire and either the moderate charring that may have occurred was left in place, or scraped off. These structures were massive in size and were built to be highly resistive to fire mainly, for the economic perspective.

When sprinkler technology came along, these factory structures were even provided with scuppers to allow water to be easily removed either by natural drainage or pushed out by salvage crews. Bottom line was just that, the bottom line and it was important to get business and commerce running again. These buildings were robust and sustained, in some cases, for 100 or more years. One key feature of these structures is that after a fire they often had plenty of mass to support the designed loading of the structure.

Fast forward to our current times and look at how engineering and construction technology has allowed us to manufacture structural load-bearing components. Ones that use the least amount of material needed to carry the load, relieve the pressure on wood as a natural resource and allow for greater efficiency to the building industry in constructing buildings.

"Throw Away Homes" Are Built

The efficiency equates to profit, but the modern home has become a "throw away home." But this is not an economics paper it is about a shift that occurred about 20 years ago in the residential construction industry that we noticed and were concerned about but really have not done much to change. I am talking about the impact on firefighter safety brought on by the so-called lightweight construction.

There are really many areas of concern related to lightweight construction, but in this issue I only want to talk in a limited scope about the impact on firefighter safety and tactics of fires that can get into the structure of the building.

Going back to the example of the massiveness of timber construction I want to move you now nearly to the other end of a spectrum of construction. We'll go through this spectrum by way of where many of us cut our firefighting teeth in forgiving structures that were mostly pretty solidly built. I grew up and started as a firefighter in a suburban area that really has developed in earnest since the late 1930's common construction for that period and the next 50 years used dimensional lumber to form wood frames for the structure; or buildings of masonry walls with wood floors and roof to form what we know as ordinary construction.

Even in the smaller dimensions of the structural members you still had a measure of mass that could give you time to conduct an interior attack with less risk of structural failure. Dimensional lumber dominated construction and when combined with plaster or sheetrock compartments you were afforded considerable resistance to fire if it started in a room's contents. In these construction types floors and roofs could become (spongy) and raise caution but would not be necessarily consumed and collapse before firefighters could effectively attack and stop the destruction of the structure.

A couple years ago, there was a house in my old neighborhood that had some electrical phase problem that fedback electricity across the ground causing all wiring in the structure to glow like a bread toaster. Fire cooked this house for 20 minutes before the power company arrived to cut the current. Firefighters extinguished the fire pretty quickly. This home -- built in 1948 -- was not only still standing but was structurally in decent shape considering the insult it endured.

In the robust wood-frame construction, especially in the middle of the 20th century when wood-frame platform construction came into use, fires infrequently breached the interior compartments exposing the building's structure. If it did it generally stayed within one wall stud or ceiling/floor joist channel. Not only was there more mass to resist the heat and degradation to the building's support system, but the closed joist and wall stud areas of platform construction afforded natural fire stopping.

What we now refer to as lightweight construction does not offer the same inherent resistance to fire. We became so used to the paradigm of an aggressive interior attack and a quick stripping of the sheetrock or plaster that it became hard wired in our culture. This went on and has actually been in place now for as many as five generations of firefighters.

Let me also mention here and now that exterior finish on these buildings was highly resistant to fire exposure and wooden decks had not yet become popular, at least in the east where a Levittown link patio of concrete or stone was most common. But in the late 70's and more the early 1980s residential construction began to change.

New Materials Used In Construction

In the 1980s we began to see a shift in construction materials for residential buildings. As mentioned earlier there was a desire by developers and builders to increase efficiency and profit and a reduction in the number of the forests formerly used to supply the nation's lumber. With more imported wood, the cost was increasing and economy dictated that innovation be employed to save resources and reduce costs.

This in some ways was probably a sense of urgency that could provide a powerful shift to more engineered products and the increased use of plastics, fiber board, and the products that were specifically designed and manufactured to have just enough load carrying capacity to meet the needs of a structure.

We began seeing dimensional lumber less frequently to carry spans of open space. More often we began seeing trusses with webs of 2-by-3 lumber and I-beams that were nothing more then 2-by-3 flanges on top and bottom and a web of 3/8-inch or 1/2-inch in plywood and composite material. But here was the beginning of change. The construction methods using plywood I-beams that have cutouts for utilities and floor trusses made out of 2-by-3's are actually the complete inverse of the platform wood-frame construction with dimensional lumber. One characteristic that these structural members present is a large combustible void space which was nearly non-existent in platform frame construction.

The voids create effective burn chambers, with plenty of oxygen, maybe even some air currents, and combustible fuel surface area. Add to the inherent combustible nature of the voids, the adhesives for all sorts of joining and connecting of structural members and you can have a violent production of hot flammable gas that moves ahead of the fire providing two sides of a fire triangle on steroids only waiting for the introduction of enough oxygen to flashover in the space. Now I want to get more specific about the danger and need for different tactics.

We are starting to have clear evidence that fires in lightweight residential construction are presenting an even greater safety risk than originally envisioned. The fires in these structures are behaving more violently. The materials are burning fiercely and very efficiently putting off higher amounts of heat and flammable gas. To the well protected firefighter they not even detect that there is a problem because they are unaware of what is going on behind the walls. Then instantaneously, the conditions move from the structural voids to the compartment trapping a firefighter in pure hell.

Separate fires killed a firefighter in Prince William County, VA, and seriously injured a crew in Loudoun County, VA. In both cases, fires started on the exterior wooden deck of a single-family home and gained easy access as it exposed and destroyed the siding; entered into the structural voids of the house then burned violently on the readily available combustible materials.

As mentioned above, I am only looking at one scenario involving lightweight construction -- fires that either enter a void from a hostile exterior fire or one that otherwise is able to start directly in or enter voids. We can no longer count on the stability of structural members like we used to. With the significant heat output and unburned, ready to ignite gases produced by modern fuel types and fire loading we can expect a different kind of hostile fire that should be assumed to be in the structure and not contained by the passive fire protection of compartmentation.

It's Time for New Tactics

New fire attack tactics must be embraced. A complete size-up, with a 360-degree look at a structure, is critical so that it can be determined if there is more then just a room involved and to see if that fire originated outside of the structure because this is important. When a fire starts on the exterior there is evidence that the first aggressive action should be to attack and knock down the fire in the exterior area of origin and its exposure path to begin to reduce the energy that can at times be fed into the structure like a blow torch. These exterior fires seem to literally pump energy in the form of heat and ready-to-burn gases into the structure and unless you stop it, it will destroy the structure and anything else in it's way, including firefighters. In the interim, the fires have shown the propensity to quickly block off the firefighters escape routes.

Blitz attack nozzles, pre-connected with a sufficient diameter and flow, can over power the fire and then an interior attack with a measure of caution is called for here. While this is counter intuitive to what had been the accepted doctrine of "attack from the unburned position" it is imperative to firefighter safety. Additionally, firefighters should use thermal imaging technology on the interior to determine if in fact that clear rooms have a hidden raging inferno behind the pristine sheet rock.

This potentially offers valuable seconds to pull back to a safe location and begin to cool the area in preparation of opening up the structure to gain access to confine the fire. There actually maybe fires so advanced in these structures that it is not possible to initially and safely make access.

The two fires in Northern Virginia are probably similar to fires elsewhere across the United States. We just have not begun to recognize the pattern. I believe that fires that get into the structure of combustible voids in the lightweight constructed homes are common but very dangerous fires. We should not treat them the same as a 1,200-square-foot brick or asbestos shingled rambler. They have already been shown to be uniquely dangerous structures to manage a fire in.

When the first arriving fire officer reviews the presented fire factors of lightweight construction, they should consider additional possibilities such as did the fire start outside, or has it extended to the structural members? Then establish a plan for how to manage the fire safely. Truck companies and others who often may go off to perform functions such as search and ventilation actions need to be extra aware of the danger.

The fire that killed Firefighter Kyle Wilson in Prince William County had no occupants in the house. They safely evacuated, but he was performing a primary search for victims. Due to the construction methods and materials and the way they so efficiently burn I have begun to call new homes "Throw Away Homes" because frequently there is nothing left. Let's not consider firefighters in the same sense and learn new ways of overcoming these challenges.

MIKE LOVE is a division chief with the Montgomery County, MD, Fire and Rescue Service and oversees all functions of life safety, community outreach and information, planning and recruiting and serves as the Montgomery County Fire Marshal. He is a graduate of the University of Maryland, the Executive Fire Officer Program and is a Certified Public Manager. Love is a member of the International Association of Fire Chiefs Fire and Life Safety Section Board, the International Code Council Code Technology Committee and the National Fire Protection Association North East Code Development Committee. Love also moderates two fire and life safety networks - one for educators called National Fire and Life Safety Educators (NFLSE) and a second called ePARADE for fire marshals and life safety professionals. Between the two forums there are over 800 members with the daily sharing of advice, news and real time life safety issues. Fire service and industry members who have an interest in either of these groups can contact Michael at [email protected].

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