Every fire district has some type of strip mall or a cluster of one-story attached commercial buildings. In some older cities, these buildings are called taxpayers.
A fire in such a structure during the night, when the business is closed, can gain extensive headway before it is detected. Following is a list of some tactical considerations.
Cockloft. A glaring weakness of taxpayer construction is the undivided common cockloft found in most of these structures. If fire gains control of this area, there is a good chance you could lose the building. The cockloft is the space between the finished ceiling and the underside of the roof. This continuous space (void) can extend the full length and width of the building with no separations to hinder the spread of fire and smoke.
Roof. The roof is usually constructed of wood joists covered with tongue-and-groove or plywood and then covered with waterproofing material. Roofs on newer construction may be Q-decking covered with insulation and some sort of rubber waterproof membrane (most common) or poured concrete with gravel covering supported by Q-decking. Both the membrane roof and the concrete roof are supported by trusses.
Lightweight open-web steel joists (Type II noncombustible construction) are not fire resistance rated. Their fire rating depends on the ceiling finish and the finished roofing material. Unprotected open-web joists have been known to collapse in less than 10 minutes.
In metal-roof deck fires in newer strip malls, when the underside of the deck heats up from a fire inside the building, heat is conducted through the decking to the bituminous adhesive used to create the roof surface. This heating vaporizes the adhesive. Since this gas cannot escape through the roof surface, the gases travel back down into the store through the joints in the metal roof deck. Once the gases mix with air, they are ignited by the fire below. This type of fire generates thick black smoke because of the petroleum component of the roof deck.
In buildings with a concrete roof deck, this is not a problem. One of the authors experienced a fire in a one-story taxpayer with a concrete roof. You may not find this type of roof often.
Parapet. Parapets are a safety concern that must be continually monitored throughout firefighting operations. The parapet is usually a continuation of the exterior wall; its weight is supported by a steel I-beam that spans the openings for the glass window displays and entrance doors. The parapet is considered a freestanding wall. Since the parapet spans a long distance and is only supported at the ends, any movement of the roof or expansion or twisting of the steel I-beam by the heat of the fire can topple the parapet. Many firefighters have been seriously injured or killed by such collapses, even after the fire had been extinguished. Parapets must be continually monitored by all firefighters, especially the chiefs or designated safety officers.
Columns. Because of the large open space in commercial buildings, columns may be used to support the horizontal beams of the cellar and main floor. A failure of a column or any vertical structural member is usually catastrophic. Columns may be made of wood or cast iron, or Lally columns. Depending on their material, columns can fail in less than 30 minutes. This is of particular concern in basement fires where the failure of a column may collapse the floor above.
Walls. The exterior walls are usually constructed of brick or concrete block. The stability of the exterior wall depends on the integrity of the roof’s structure. In taxpayer construction, with four block walls approximately 10 feet high, the walls remain relatively unstable until the roof beams are laid to give the top of the wall lateral support. Even though the block may be tied together at the corners, once the roof beams are burned away, you are left with a freestanding wall that could be a collapse hazard. The roof beams are literally holding up the wall by a system of lateral supports. Interior partition walls that separate stores are usually of wood or metal stud construction with either gypsum board or plaster. Interior walls usually only extend to the ceiling and not into the cockloft.
Ceilings. In older buildings, the original ceilings were made of lath-and-plaster or decorative tin panel (tin ceiling); they can be as high as 12 feet above the main floor. Though these ceilings may still be in place, it may not be the ceiling you see when you enter the building. Because of renovations, a second or third ceiling might have been installed under the original one. The ceiling you see may be gypsum board or the more commonly used drop ceiling. Since the old ceilings are usually not removed, they create voids for fire travel. These ceilings can represent a major collapse hazard and can be blown down by backdrafts or collapse from fire, heat, water damage, or improper installation.
In the early stages of the fire, check above the drop ceiling with a pike pole to determine the condition in the cockloft and the construction design of the roof. Whenever checking any ceiling space, do so from an area of safety and have handline protection with you. Backdraft conditions may exist in the ceiling space and the introduction of oxygen may ignite and collapse the entire ceiling, trapping firefighters farther inside the building. Rely on information supplied by your roof team to help determine this.
Cellars.Do not assume the cellar will conform to the layout of the stores above. One occupant may use parts of the cellar that extend under two or more stores. Cellar access can be found outside (a sidewalk trapdoor) or inside the structure. The inside opening may be a trapdoor located at floor level somewhere within the store or may be a door with stairs leading to the cellar. These openings (usually toward the rear of the structure) are difficult to find with the lights on and are almost impossible to see in a smoke condition. Using vertical ventilation, a thermal imaging camera, and search rope are mandatory when searching for fire in this type of cellar.
Security gates. For years, storeowners have used metal security gates to protect their stores against burglary. Even in low-crime areas where no security gates are on the front of the building, you will find gates on the windows, steel buck doors, or roll-down gates at the rear.
Overcoming these security features can delay access to the building and discovery of the fire. A power saw with a metal cutting blade or a cutting torch is needed to cut locks or the gate. Remember, when the gates are in the open position, they place an eccentric load on the parapet.
Showroom windows. In newer type or Type II construction, openings in the front of the building usually will have an aluminum frame holding the showroom window glass; older buildings may use wood frames. The glass usually will be 1/4 inch thick and can be plate glass (most common), laminated glass, or tempered glass.
Plate glass, when broken, will fall in large pieces, which can easily injure a firefighter. Laminated glass, the type used in automobile windshields, is more difficult to break because of a plastic membrane located between the layers of the glass. You must break the perimeter of the glass and attempt to remove it in one piece. Tempered safety glass, used on the side windows of automobiles, will break into thousands of small pieces. The type of glass you will encounter when venting windows will be almost impossible to determine beforehand.
The entrance door will be tempered glass or laminated glass surrounded by an aluminum frame. These doors use aluminum mortise locks, which can be easily forced using a K tool. Venting the glass instead of removing the lock damages the door’s integrity. Firefighters will have to crawl over broken glass, risking injury, and hose will be subject to damage as it is advanced on the fire. Additionally, you will still have to maneuver around any horizontal hardware on the door and the frame itself. If entry is gained by removing the glass and not forcing the door, you will have to remove any horizontal hardware.
Signs. Store signs attached to the front of the building must be monitored. These signs are usually secured to the building, and fire conditions can damage sign supports. Overhangs built to modernize the buildings can create a huge void that can extend the width of the building. Eccentric loads are usually supported by unprotected steel, which has a very poor stability record when affected by fire.
Change of use. It is rare that the use of a commercial occupancy will remain unchanged over the life of the building. Many times, the property’s owner will make substantial changes to the building to accommodate new tenants; these changes can hide the building’s original design. For example, a building originally used as a supermarket may be subdivided into three or four specialty stores. New signs and false facades would hide the old supermarket’s bowstring truss roof. Changes in occupancy also mean that the sprinkler systems (if present) probably were not changed with the occupancy and may not be able to handle the new fireload.
Occupancy use. Hazardous materials may be on the premises in many of the most common commercial business. Dry cleaners, hardware stores, and swimming pool businesses are all examples of occupancies that routinely have combustible material on hand.
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Remember, fire can gain considerable control of these buildings at night when the business is closed. Use extreme caution when undertaking your attack. Closed-up buildings in which fire has been burning unnoticed may also present backdraft conditions on arrival-adjust tactics accordingly. The more you know about the building, the better your chances for a successful operation. ■
■ JOHN MILES is a captain with the Fire Department of New York, assigned to Division 6. Previously, he served as a lieutenant with Ladder 35 and as a firefighter with Ladder 34 and Engine 82 and as a volunteer firefighter with the River Vale (NJ) Fire Department and the Spring Valley (NY) Fire Department. He is also an instructor with the Rockland County Fire Training Center in Pomona, New York.
■ JOHN TOBIN, a 30-year fire service veteran, is assistant chief and training officer with the River Vale (NJ) Fire Department, where he previously served as chief. He has a master’s degree in public administration and is a member of the Bergen County (NJ) Fire Academy Advisory Board.
