Stripping down strip mall fires
Reviewing building construction, unique hazards, and mistakes and lessons learned from fires in these dangerous occupancies
Editor’s Note: The FireRescue1 Academy includes the Fire Reality Training Video “A Strip Mall Wall Collapse.” Visit the FireRescue1 Academy to learn more and to schedule an online demo.
In the age of convenience and one-stop shopping, it should come as no surprise that there are over 100,000 strip malls and similar businesses in the United States. Nearly every community has at least one; however, many fire departments are not prepared to respond to a fire in one of these establishments.
Generally speaking, a strip mall is a row of businesses that share a common roof and are separated by partitioning walls that commonly reach the ceiling, leaving the attic or cockloft open over every occupancy. In this article, we will discuss some common characteristics of the strip mall, including building construction, unique hazards posed by these occupancies, as well as initial tactics. We will investigate some of the flawed logic behind common, albeit incorrect, approaches to fighting a fire in these types of buildings, and offer options to help avoid a negative outcome.
Strip mall building construction
Early strip malls were built to last, using Type III materials, such as masonry-bearing walls and a roof assembly dimensional joists, commonly measuring 2 x 10 inches and 1 x 6-inch tongue-and-groove roof decking. Although these buildings may have a noncombustible frame, the roof covering is made of combustible materials. In many cases, the roof of these structures will fail and collapse long before the walls of the structure lose integrity. Consider that many of these structures were build or re-roofed with plastic foam insulation board. The insulating properties of Type II construction with a heavy and likely synthetic fire load will channel the heat, smoke and flames up toward the combustible materials that comprise the roof, leading to catastrophic failure.
It should also be noted that in modern construction, the structural members of Type II buildings are being built with aluminum framing. This construction style is becoming more commonly known as “low mass,” as they are much less dense compared to Type IV or Type I construction. Since there is no fire retardant on the framework, the heat from the fire load will cause the members to elongate as much as 4 inches per 100 feet. This change in dimension will weaken the members, ultimately leading to structural collapse.
Type V construction, on the other hand, is built completely using combustible lightweight engineered wood structural assemblies, such as parallel joist trusses or I-joists. Depending on the region, age of the building, renovations over the years and code requirements, these buildings may have large void spaces between the roof and one or more ceilings. This can allow smoke and flames to spread laterally without being noticed and allow for the fire to advance significantly before the alarm is sounded. As the fire spreads, growing in size and intensity, several structures that are common in strip malls, such as parapet walls and façades, can become compromised.
A parapet wall – a wall that extends above the roof line on the front side of the structure – is typically supported by an unprotected steel I-beam that bears the weight of the wall above the store windows and frontage. As the fire progresses and the I beam is exposed to heat, it will begin to warp and weaken. This can result in failure of the entire wall, causing collapse of the parapet, including sections that are above occupancies not involved with the fire.
The construction danger doesn’t end with parapet walls. Façades are an architectural feature that are designed to provide protection from the elements as well as hide rooftop equipment, such as HVAC units. There are two types of façades, differing in how they attach to the building.
A true mansard is an extension of the actual roof structure beyond the front wall of the store. Because this type of façade is an actual part of the building itself, collapse risk is less of a concern. The second, and more concerning, type is a cornice. These façades are also known as false mansard or “eyebrows.” Cornices are attached to the store front using carriage bolts or masonry fasteners. As the fire progresses, and vents through the glass frontage of the occupancy, the cornice can become weakened and eventually collapse, bringing the parapet wall or other structures with it.
Prefabricated lumber, such as particleboard or oriented-strand board (OSB) provides a cost-effective alternative to the dimensional lumber of old. This type of lumber is comprised of small pieces of lumber that are pressed together using glue to form one solid board. As the fire advances, and the OSB is exposed to heat, the glue melts, weakening the strength of the wood and further fueling the fire with synthetic chemicals. Fire conditions in this type of structure will rapidly accelerate, causing the fire spread like a box of matches.
Additionally, modern construction using Type V lightweight framing is being hidden behind brick façades, making the building appear to be Type II. As the wood frame fails, the brick façades pose a much higher likelihood of collapse.
As we look higher, toward the roof line, we are met with even more challenges – the danger of load concentration due to heavy machinery, such as air handlers and HVAC units, and the difficult task of ventilating through a built-up roof. HVAC units pose a grave danger to the interior firefighter due to their weight dead load being concentrated in one spot on top of a weakened roof. As the structure of the roof below weakens due to fire load, the weight of the HVAC unit will sink until it finally falls through the roof and into the structure. Monitoring the stability of these units is paramount for the truck company working on the roof.
In terms of ventilation, there are few roof designs that will provide more of a challenge to firefighters than a built-up roof. The elements are simple, however, when combined, they can create a unique problem when ventilating. These roofs are constructed using several layers of material, including expandable foam, plywood or OSB, Styrofoam, a rubber water barrier, tar paper and gravel. Often, even after successfully breaching the upper level of the roof, the ventilation crew finds themselves faced with additional layers of obstructions, such as previous roofing or dropped ceilings from below.
Strip mall fires: Not your “average” fire attack
An all-too-common and often dangerous tactic that I have seen is the “cookie-cutter” mentality of firefighting. It seems that through muscle memory, we have forgotten to apply what we observe in the initial scene size-up toward our actual tactics.
As a general rule, a 1¾-inch hand line, while appropriate for a residential structure, is going to fall short of the needs in a commercial strip mall fire. Looking at the numbers, the average strip mall ranges from 5,000 to 10,000 square feet per occupancy. First-arriving companies must take extra caution to avoid defaulting to the “normal” operation of taking a small handline through the front door.
Inside the business, you are likely to find even more differences. Although some of the furnishings may be the same – a few chairs to sit on or a table or countertop – being out of the comfort zone of bread-and-butter operations can lead to confusion of your surroundings and, even more dangerously, disorientation. Add to that the limited ingress and egress, especially at the rear of this type of building, and you can see just how quickly this mentality can become a threat.
The two best ways to avoid this issue: pre-fire planning and a clear and concise scene size-up by the incident commander (IC).
Strip mall pre-fire planning and on-scene size-up
A good scene size-up starts before the bells ever ring. Having an updated and accurate pre-fire plan of action for businesses in your district is critical to staying ahead of the fire.
With that pertinent information already in place, the IC must then consider several factors:
- Life hazards
- Size of the structure
As the first companies arrive, the first priority is to determine if there is anyone trapped in the building. We must also be mindful of the hazards to our own lives. This is where building construction and structure layout will benefit you tenfold.
Knowing what businesses are currently operating in each of the shops can give you a better idea of what type of fire load you may be dealing with. Knowing that there is, for example, an auto parts store in one unit and a paint store in the unit next to that should heighten your sense of awareness to a rapidly progressing fire condition, should the fire involve those areas.
Every fire has six sides. Front, back, left, right, top and bottom. A fire in a strip mall presents a far more complex equation. The initial fire has six sides, however, as the fire spreads to an adjoining exposure, that fire now has six sides as well. As the fire continues to spread, the exposures and the number of sides of the fire also continue to grow. This process will continue until either all of the units are involved or the fire has been controlled.
The size of the building has a direct effect on the level of staffing that will be needed. In consideration of the question, “Do I have enough personnel?” the answer will almost always be “No!”
Use the information gathered about the occupancy, time of day and size of the building to make an early determination of whether additional resources will be needed. Remember, the larger the building, the more places for smoke and flames to hide undetected. Performing a 360, even if it is done from the apparatus on approach, will allow you to apply all of this knowledge to your decision-making before you even step out of the rig.
Strip mall mistakes and lessons
National Institute for Occupational Safety and Health (NIOSH) investigation reports can be a helpful tool when planning for a fire in a strip mall. Contributing factors in several of the cases I have studied are similar in nature.
Crew integrity: Crew integrity or company mentality cannot be stressed enough at such a large-scale event. Freelancing must not be tolerated. Companies should perform tasks in groups no smaller than two; however, three or four is preferred. Maintaining a company mentality has a direct connection with another common contributing factor to firefighter death: disorientation.
In a large commercial structure, even one separated into smaller units, it can become very easy for an individual to become disoriented or lost. Once this happens, it becomes increasingly more difficult to locate the lost firefighter. By maintaining your crew integrity, you provide an extra level of protection against becoming separated and experiencing a mayday event.
Air supply: Another mistake often made on both residential and commercial fires is failure to properly manage air supply. We are always looking for five more minutes inside. We stretch our limits, and that is what gets us into trouble. It is important to remember that it will take just as long, if not longer, to get out of the structure as it did to get into. Leave yourself enough time to accommodate for the unexpected.
One factor to consider is where the seat of the fire is located. If there is strong evidence that the fire is located in the rear of the structure, it can be beneficial to air management and remaining oriented to stretch the attack line from the rear of the structure and minimize the distance traveled into the building. No one should be waiting for their low-air alarm to go off to decide to exit the structure. There should be a constant level of communication between both your crew and Incident Command regarding the needs of the crew, including the need to exit the structure for a fresh SCBA bottle.
Collapse zones: Given the many different obstacles that first-arriving companies face, it can be difficult to remember the dangers of operating inside of the collapse zone. The rule of thumb for calculating the area of the collapse zone is the height of the building multiplied by 1.5. Extra care must be taken to not only ensure that apparatus are positioned outside of this area, but also that firefighters who are engaging in active firefighting have a heightened sense of situational awareness when it comes to structural integrity. As previously mentioned, a fire can burn unchecked in the void spaces above a dropped ceiling or behind a façade, leading to a total collapse in the front of the structure, including areas that may not be involved in the initial fire.
Coordinated attack: Finally, suppression of the fire and ventilation must be a coordinated team effort. Ventilation without ongoing suppression efforts can lead to a change in the flow path and draw the fire beyond where it normally would have gone. The company assigned ventilation must communicate with the IC, who must, in turn, communicate with the suppression crew to ensure that they are getting water on the fire before the first window is broken or hole is cut. The suppression team must also make sure that they are providing adequate water for the fire load, allowing for a good knockdown to be achieved.
Stay one step ahead of a strip mall fire
A fire in any commercial building is a high-risk/low-frequency event. These emergencies are even more inherently dangerous than our typical house fire. However, a fire occurring in a strip mall adds additional dangers and should be considered one of the most dangerous situations that a firefighter will face in their career. Using sound judgment along with a solid foundation of building construction and fire behavior will allow the responding companies to be one step ahead of the fire before it occurs.