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By Douglas Fishel
Many of us have seen videos that illustrate the progression of test fires from the incipient stage through the full free-burning stage. One of my favorites is the room-and-contents fire that burns in only a few minutes. The other is the firefighter safety demonstration of the flashover scenario. Only a few of us—I hope very few—have observed a fire start in an occupied building and watched it grow until the fire department arrives. That is what happened to me on a chilly January evening.
I was finishing work in my shop and happened to check my heating system to find it malfunctioning when it flashed heating oil through the access door. The fire extended to the open rafters above and ignited the bird’s nests that were built over the years by barn swallows. The furnace room is attached to the main shop at the roof level, and the sticks and grass from the nests extended into the closed attic area above the shop.
I heard the unmistakable crackling noise of fire coming from above, so I ran upstairs to the loft to access the unoccupied attic. Climbing up and looking across the ceiling, I saw the flames beginning to climb up the trusses and the roof. I ran to my house, about 50 feet away, to tell my wife to call the fire department because the garage was on fire. Returning to the garage, I pulled the only hose that was available to me, a preconnected pressure washer. As I climbed the ladder to the attic, the smoke conditions had severely worsened, but I started to hit the fire with this “high-pressure fog,” and the fire started to blacken down. By then, there was an area approximately 16 feet long, involving the bird nests and the wall and ceiling assembly of the building. The pressure washer was holding the fire and preventing any further extension to the roof trusses. The elapsed time was no more than three minutes until I had water, limited as it was, on the fire. Waiting for the arrival of the first engine, I reminisced about the early years when some companies used the Darley “High Pressure Fog System,” and I laughed to reassure myself that my pressure washer had to be similar.
Living in a rural area means that we depend on an all-volunteer fire department to respond to our emergencies. We have an excellent group of dedicated men and women who serve in this capacity. It was not too long until some firefighters arrived in their privately owned vehicles and took the universal appropriate action when you still have occupants in the burning building: “Tell the idiot on the ladder to get the heck out of the attic.” My answer was, “Not until you get a charged line up here!” Lying flat on my stomach allowed me to breathe fresh air. I was not too concerned about the fire at that point, as my high-pressure fog was holding the fire; but, because I had built the building, I also knew the attic is naturally vented and that that venting would allow the fire to extend up to the roof peak as soon as I stopped flowing water. The attic would be fully involved in minutes.
The first-due engine arrived and stretched a 1¾-inch line to the attic and a second line to the burning interior wall. As agreed, I, “the idiot on the ladder,” traded places with a firefighter appropriately dressed in personal protective equipment. I went outside to get some good air and watched the remainder of the attack.
There was a small delay in charging the “attic line”; it had to be disconnected and extended. In those very few minutes, the fire began to extend to the trusses again, as I had predicted. I could see the metal roofing starting to glow above the fire. As I stated earlier, the natural airflow through the soffit and peak vents feels like a wind tunnel if the wind is blowing, and that night was no exception. There was enough heat impingement to melt the vinyl roof peak vent. The fire was soon extinguished, and the walls and ceiling were pulled for a good overhaul. I am grateful to everyone who responded to save my building.
Commentary on Critical Observations of the Above Incident
Following are my observations, lessons learned, and lessons reinforced from incidents involving pole structures.
Opening Incident
Five minutes of flame and heat on the truss gusset plates caused three plates to release and one to fall completely off. The truss assembly had failed that quickly. In June 2013, Gregory Havel, in his article “Construction Concerns: the 20-Minute Rule” (fireengineering.com, June 11, 2013, http://bit.ly/1Cto0Nbp), discussed whether the standard 20-minute fire attack rule regarding safely entering and attacking a well-involved fire still applies today. He said it does not apply any longer because new buildings are constructed with lightweight construction instead of the legacy construction used in the past. He is absolutely correct. If this fire had been allowed to burn until the first-arriving engine made an attack, the entire attic would have been involved and all of the truss assemblies would have failed. I did not discuss the type of building construction yet, but it gets even scarier when I tell you that the structure discussed above is a “pole building” and has a truss only every four feet!
Pole buildings are common in many areas. You may recognize the proprietary name of Morton Buildings, a successful building company that builds pole buildings. The company name is colloquially used to identify this type of structure, although the structure may not actually be a Morton.
Another term for this type of construction is “post-and-frame construction.” These buildings are constructed faster and much less expensively than stick-built buildings. Once they are covered with siding, they look like any other building. The occupancies range from storage to horse barns to residential housing units. I have seen some with a commercial workshop on the first floor and an apartment on the second floor, the rural version of the taxpayer.
The buildings are built with a post buried below the frost line and spaced every eight feet. The 2- × 4-inch boards (girts) are nailed horizontally to the roofline every two feet from the ground. Metal siding is attached to the girts. This transfers roof and side loads to the posts and to the ground. The roof has free-spanning trusses normally placed every four feet. A saw cut is made in the post for an attachment or a connection point. Every other truss has no post on which to rest, so it is nailed to the girt or bandboard.
The roofing material is attached to 2- × 4-inch purlins, usually 25- or 29-gauge metal, nailed every two feet perpendicular to the truss. However, I have also seen plywood and shingle roof assemblies. The completed building is very strong and is rated for the wind and snow loading common for the area in which it is built. All of the components complement and co-depend on each other to attain this strength.
The interiors can be finished; steel panels are popular for use on the walls and ceiling. That is the reason these structures become dangerous after five minutes of heavy burn. Remember, the trusses are free spanning the entire width of the building and are spaced at four-foot intervals (some even at eight-foot intervals) with weak attachment points. In addition, builders hang the steel ceiling panels directly to the underside of the inherently weak truss assembly. Then come the layers of insulation above the ceiling. Now, a garage door (or more) with its track and electric motor closing operator is hung from the same trusses. Lights, wire conduit, cord reels, air lines, and anything else that needs to be mounted are hung on the ceiling assembly and the truss. All of this dead load goes unnoticed until it burns. Add an attack line that has been flowing for a few minutes and soaking into the insulation. How much weight is now hanging from an assembly secured with a few wood screws? The entire ceiling and roof assembly is just waiting to fall. The incident commander should ask the questions: Do I want anyone under that ceiling, and do I want firefighters to pull it for overhaul?” The answer is obvious: No way! Conversely, the only safe way to work on the roof is from a ladder truck. Do not add to the roof load by getting on it.
Other Incidents in Pole Buildings
One evening in February 2014, our department was dispatched to a detached garage fire. Within minutes of the chief’s radio message that he was responding, the dispatcher came back with “at least five callers reported heavy fire in the roof area.” His size-up report on arrival six minutes later noted a 72- × 42-foot garage heavily involved, with fire venting through the roof. The chief ordered the first-in engine to drop a supply line and deploy the preconnected master stream device. The first two engines and a tanker initially supplied the attack water because the hydrants were covered with snow as a result of plowing during a recent snowstorm that had dropped 13 inches. After “digging” the hydrant free of packed snow, the five-inch large-diameter hose was supplying the attack engine from the municipal water system.
The homeowner was available to unlock the overhead doors; this made it quite apparent that a very heavy fire load was at hand. The single master stream was making good progress on the fire, but since the water supply was intermittent, the contents would begin to free burn again until the next engine supplied water. After the hydrant system was flowing, a second line was added to the attack, and the fire was under control quickly. Because of the burning contents, a very heavy black smoke condition made it difficult to see to direct the attack. The heavy burn time and potential snow dead-load conditions on the roof made it impossible to ventilate from the roof. Fans were deployed, and limited overhaul was undertaken. The operations chief limited the number of personnel entering the structure because of the safety issues associated with this type of construction.
As mentioned earlier, occupants add dead loads throughout the life of the building, including steel ceiling panels attached directly to the underside of the truss, layers of insulation above the ceiling, and a garage door with its accompanying parts. Then, lights, wire conduits, cord reels, air lines, and anything else that needs to be mounted or stored are hung on the ceiling assembly and the truss. This fire building was no exception, although it had no ceiling assembly. No one could determine this initially because of the smoke conditions.
Dead Load and Post-Fire Conditions
Photos 11-13 show just how much of a dead load was hanging above us or mounted on the unprotected trusses and hidden by the smoke, waiting to fall on us, and some of the results of the fire on the construction.
Fortunately, the fire in this building had extended high above us because there was no ceiling assembly. The truss assemblies failed at the highest connections but remained intact on the horizontal legs of the truss roofing assembly, transferring the roof load to the horizontal girts and bandboards. This demonstrates the reliance and co-dependence of the “assembly” to maintain strength. In this fire, much of the added dead loading—lawn mowers, wheelbarrows, lights, and so on—had fallen or were dislodged by the master stream during the attack phase of the fire. Even so, quite a bit of the overhead hazards remained after the fire.
Get out in your first-due areas and observe a post-and-frame building under construction. Do it quickly because they go up and are finished in a matter of days. Most builders are willing to talk to you about the building techniques they employ. Create a specific guideline for operating on this type of building construction.
The first engine probably will not be able to have water on these fires within five minutes from notification or dispatch. Depending on the occupancy/use, the fire load may quickly exceed available water supplies, and any heavy fire in the occupied area will extend to the attic area quickly. These are master stream, exterior, defensive attacks. I have addressed the majority of failure and collapse issues. I have seen the collapse of these building types during construction because every component is dependent on each other for the strength; prior to completion, the building is vulnerable. Many of us can also relate to fires that start in buildings under construction. The result is a large, fast moving fire in a very unsafe structure. If you have to respond to a fire in this type of construction, you may not save the building. In reality, it probably was fire loaded and a loss when you were dispatched. If you approach these fires with a plan, stay off the roof, and use a transitional, or even a defensive, initial attack. You won’t lose or injure any personnel from a structural collapse that is predictable and inevitable.
Although, in this case, water supply and weather (snow) conditions hampered the fire attack initially, sometimes we fail to realize a blessing in disguise. The intermittent water supply allowed a “controlled” melt off of the recent snow. The heat loosened the snow, which slid harmlessly off the roof, reducing the loading that would have contributed to a collapse. The lack of a ceiling assembly allowed the fire to extend high and destroy the upper members of the roof/truss assembly without great damage to the bottom horizontal leg of the truss that supported the dead load of materials and tools hanging on the truss or added over the years by the owner. Additionally, a ceiling would have held the fire heat below the ceiling, preventing the melting of the snow. The ceiling would have held water loading from the attack lines. Any significant fire would have extended through the ceiling assembly after time and weakened the horizontal leg of the truss, contributing to a failure of the ceiling assembly and a dangerous collapse.
All in all, the crews did an exceptional job and made a great “stop.” Many of the collector cars and other contents in the structure were saved. The building will be repaired, and no one was injured. In my book, this is a win-win for everyone involved.
Additional Links
http://emberly.fireengineering.com/articles/2015/02/indy-pole-barn-fire/image-gallery.html
Construction Concerns: Types of Construction
DOUGLAS FISHEL retired as a firefighter/paramedic from the Anne Arundel County (MD) Fire Department, where he served as an acting battalion chief of special operations. He is a volunteer and life member of the Gettysburg (PA) Fire Department with more than 30 years of service and volunteers with the United Hook and Ladder Company (New Oxford, Pennsylvania). Fishel is a master instructor with the Pennsylvania Fire Academy and has a BA degree in organizational management and an AA degree in EMS administration. He is also a National Fire Academy alumnus.
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