PARAPET COLLAPSE:A SERIOUS DANGER FOR FIREFIGHTERS

BY THOMAS DUNNE

On April 4, 1956, tragedy struck the Fire Department of New York (FDNY) when six firefighters died while operating at a fire in a furniture store. They were killed by the collapse of the front parapet of a common brick and wood joist commercial building.

One-and two-story buildings of this type are still routinely found throughout the country; they usually contain a variety of small retail stores or a supermarket. Generally, they will also have large plate glass display windows in the front.


Photo 1.

Although construction techniques in the newer strip malls vary, the older brick and wood joist buildings will have a freestanding exterior extension of the front wall that can reach up to several feet above the roofline. This brick extension, or parapet, represents a serious collapse danger for firefighters.

Regardless of the location or occupancy, these buildings have consistently presented recurring fire problems, in-cluding rapid horizontal fire extension, backdraft potential, and parapet instability.

On July 28, 2002, FDNY units responded to a fire in Manhattan in this type of building that involved a major parapet collapse and eventually required a fourth-alarm assignment for extinguishment.

THE FIRE


In many respects, the fire building was very similar to the building involved in the 1956 fire. It was a one-story, 100- 2 75-foot, brick and wood joist building that contained six retail stores. The front of the building faced a street, the exposures to the left and rear were both six-story brick and wood joist tenements, and the exposure to the right was also a street. (See Figure 1.)


Photo 2.

Dispatchers received phone calls at 0606 hours on that Sunday morning reporting a store fire; the first units arrived just minutes later. As the on-duty deputy chief, I arrived at the scene at 0622 hours and, assuming that the fire had been “cooking” for a while, immediately transmitted a second alarm.

We deployed 21/2-inch handlines to extinguish visible fire in the stores and vented the roof. On discovering pockets of fire in the cockloft, I ordered a third alarm struck to provide personnel needed for relief and further overhauling.

When it became apparent that fire in sections of the cockloft would be difficult to extinguish with handlines, I called for a fourth alarm, ordered the withdrawal of all members from the building, and told personnel to prepare for an outside operation. Considering the time of day and our inability to completely extinguish the fire with an aggressive interior attack, firefighter safety was my paramount concern.

We established a collapse zone and eventually positioned four tower ladders and two portable deck gun nozzles for a heavy-caliber exterior attack.


Photo 3.

The exposed tenement buildings were not initially threatened, because 20-foot-wide alleyways separated them from the fire building. However, the two handlines positioned in each building provided precautionary protection of the tenements and another means of applying water to the fire building.

In the exposures, personnel monitored carbon monoxide levels and found them to be elevated, necessitating resident evacuation until CO readings lowered and the moderate smoke condition abated.


Photo 4.

Approximately 40 minutes after I withdrew all personnel from the fire building, most of the front parapet collapsed onto the sidewalk. It is worth noting that there were absolutely no indicators of an imminent collapse (no change in fire volume or smoke, no visible cracks, no noises) prior to the parapet coming down. The only “warning” was the subtle realization that the fire was slowly but inevitably weakening the forces that supported this free-standing building component.

The exterior attack continued throughout the morning; the fire was under control at 1003 hours. The loss of the businesses was a blow to the community; one of the stores, a pet shop, suffered the loss of dozens of animals. However, the surrounding tenements were protected, and the fire was extinguished without any serious firefighter in-juries.

COLLAPSE ANALYSIS

Photo 1 shows the extent of the parapet collapse (approximately 50 feet). Considering that a cubic foot of brickwork weighs about 100 pounds, this collapse involved approximately 30,000 pounds of debris instantaneously dropped onto the front sidewalk from a height of about 10 feet. The damage it could have done is frightening.


Photo 5.

Photos 2, 3, and 4 illustrate the construction details of the parapet, which is essentially a huge weight of masonry resting on only one beam. The decorative brickwork and “coping stones” resting on top of the parapet added to its weight and instability.

These photos also show the steel rolldown store gates, which are routinely pushed to the “up” position to determine the extent of fire in this type of building. In this position, they concentrate a great deal of weight and present their own collapse hazards.

Photo 5 clearly shows the bowing of the steel I-beams, which ran from the front to the rear of the building. The heat of the fire will generally make the beams expand and push the parapet outward. However, this bowing may also eliminate the parapet’s support. Every component of a building has the potential to affect another part. The failure of one area can contribute to the failure of another.

These photos also show several lightweight canopies cantilevered from the front of the stores. The parapet collapse in 1956 was in part caused by the weight of a large marquee that hung from the front of the store. Although these canopies did not present nearly as much weight, they may have provided some leverage to an already weakened wall. Conceivably, the way they were anchored to the parapet may have also slightly compromised its integrity.

LESSONS REINFORCED

Late-night commercial fires. When responding to a fire in a commercial occupancy during late night/early morning hours, consider the possibility that the fire has been burning since closing time and may have had several hours to damage the structure before units even arrive at the scene.

•Parapet dangers. A masonry parapet collapse is a deadly consideration for firefighters. When operating in buildings that have them, monitor the walls for any signs of cracking or bowing. Any firefighter noting such signs should notify the incident commander immediately. Bear in mind that a parapet may collapse a long time after you start firefighting operations. As Vincent Dunn points out in his book Collapse of Burning Buildings (Fire Engineering, 1988), the parapet that killed the six firefighters in 1956 collapsed after the fire was under control.

•Collapse zones. Once established, they must be rigidly enforced. They should extend from the building a distance at least equal to the height of the parapet. As occurred in this fire, much of the wall is likely to come down at the same time. Therefore, the collapse zone must extend far enough horizontally to include the entire building. Use barricade tape to help enforce the collapse zone.

•Exposures. In addition to checking for fire and smoke extension, check surrounding buildings for carbon monoxide buildup, and evacuate occupants when necessary.

•Withdrawal of firefighting personnel. Personnel at this fire operated in the correct manner—i.e., they quickly withdrew from the fire building when ordered and maintained their distance from the collapse zone. Their disciplined actions allowed us to extinguish the fire, protect the exposures, and avoid the serious injuries or deaths that could have resulted from this collapse.

In the 46 years that separated this incident from the tragic 1956 fire, the world has experienced many dramatic changes. However, the danger of parapet collapse in this type of structure is virtually the same now as it was in 1956. Parapets sit on top of many buildings in cities and towns across the country, awaiting the fire or other physical force that releases their deadly potential.

On August 10, 2002, an employee of a store in just such a building in New York City was on a break and stood on the sidewalk in front of the building. The parapet suddenly collapsed and killed him. This occurred without a fire—the wall had been weakened by other factors.

Any firefighter who takes the time to study the construction and collapse history of parapets will undoubtedly view them differently at his next fire. An awareness of their danger can be a vital first step in preventing injury or death in the future.

Photos by author.

THOMAS DUNNE is a deputy chief and 21-year veteran of the Fire Department of New York with experience in midtown Manhattan and the Bronx. He is a graduate of Fordham University and an instructor at the Westchester County (NY) Fire Academy.

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