FIRE IN A STRIP WAREHOUSE

The following photos document a fire that occurred in a strip warehouse in Miami-Dade County, Florida. This fire presented many of the classic hazards and difficulties associated with these types of buildings and may be a useful case study for fire departments that have strip warehouses in their jurisdictions.

Strip warehouses are becoming one of the most common commercial buildings because they can be constructed rapidly and rented to a multitude of mercantile, industrial, and storage occupancies.


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Photos 1, 2. This fire building was occupied by a variety of auto repair and paint shops, used tire and auto parts stores, and furniture refinishing businesses. The fire occupancy was a cabinet shop with a heavy fire load of wood, flammable adhesives, and finishes. This fueled a rapid, intense fire that caused the roof to collapse within 10 minutes after the fire companies arrived.


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The building was built on a concrete slab with no basement; however, consider that belowgrade oil change pits often are found in strip warehouses with auto service facilities.


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The exterior walls of the fire building and dividing walls between occupancies were constructed of concrete block. Strip warehouses built within the past 10 years are more likely to have concrete “tilt-up” walls or lightweight corrugated metal walls supported by unprotected steel columns and frame. Fire officers should not put too much faith in walls dividing strip warehouse bays. Their integrity as fire barriers may long have been violated by tenants who expand their businesses by renting an adjacent warehouse bay and then breach openings in the dividing wall.


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Photos 3-5. The roof of the fire building consisted of a metal deck supported by unprotected steel bar joists. This is typical strip warehouse roof construction. Its early collapse is also quite typical and came as no surprise, given the intensity of the fire and a metal deck roof’s vulnerability to collapse.


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A metal deck roof can also spread fire along its underside when heat impinging on the roof decking begins to melt, vaporize, and eventually ignite the thick layers of tar and tar-impregnated felt paper applied to the topside of the roof for waterproofing.

Roofs of modern strip warehouses may also consist of plywood or oriented strand board (OSB) decking supported by lightweight wood parallel chord trusses. This roof is also prone to early and sudden collapse. Strip warehouses in South Florida are commonly constructed with roofs of precast concrete twin “T”s. Don’t let the presence of massive concrete fool you into thinking that these members have any appreciable fire resistance. Twin “T”s have imbedded steel cables that are tensioned to thousands of pounds. Fire impinging on these members can spall the concrete and expose the cables, causing them to lose their tension. This causes the twin “T” to sag, slip off its bearing surface, and collapse.

Roof collapse in strip warehouses is hastened when tenants suspend heavy, undesigned loads-such as engine hoists and storage shelves-from the bottom chords of trusses. Auto shops are notorious for hanging engine blocks, transmissions, and tire racks. I recently visited a boat repair shop in a strip warehouse that had several large outboard motors hanging from the trusses. The fire building was replete with dangerous, illegal interior construction that is all too common a problem with strip warehouses. Since these buildings are constructed as open warehouse bays, it is very common for tenants to build their own offices, sales areas, and storage lofts. The construction usually takes place at night or on weekends to avoid detection by building department inspectors. Consequently, the fire building contained many interior structures that are essentially poorly constructed wood-frame shacks.

Offices and sales areas, built at the front of warehouse bays, seldom reach the underside of the roof. This makes the top of these structures convenient for storing heavy, undesigned loads such as transmissions, car batteries, pallets of floor tile, and rolls of carpet.


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Photo 6. First-arriving companies encountered extremely heavy smoke that blanketed the area, making it difficult to rapidly determine the location of the fire. The design of the fire building further complicated matters. This was a large complex of strip warehouses. Each building was more than 400 feet long and consisted of rows of bays or tenant spaces built back-to-back along a center dividing wall. Each row fronts on its own dead-end driveway. This made it difficult to determine which driveway responding apparatus should take to reach the fire.

The center dividing wall also creates another classic strip warehouse fire problem: There are no doors at the back of these 100-foot-deep bays to provide ventilation or serve as a safer, more direct means of attacking a fire burning in the rear of an occupancy.


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Because of the difficulties in locating the fire and selecting the correct entrance driveway, the first-arriving company officer ordered his apparatus and all responding companies to stage on the street outside the complex while he proceeded on foot to investigate. This was a smart move, as a hasty, premature commitment of apparatus could have resulted in companies’ taking the wrong entrance driveway on the wrong side of the center dividing wall and being unable to reach the fire.


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Photos 7, 8. The second-arriving engine company established a water supply. On arrival, the crew located the closest hydrants, flowed them to ensure they were in service, and stood by awaiting orders to forward lay a five-inch supply hoseline to the first-arriving engine.


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Photo 9. Large-diameter hose provides large volumes of water, but it can block access for apparatus. To minimize this, an engine company laying large-diameter hose from a hydrant should avoid pulling too much hose at the hydrant. Otherwise, the excess hose will form a large loop that partially blocks the street. Additionally, all hoselines, but especially large-diameter hose, should be laid on the side of the street, as close to the curb as possible.


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Photos 10, 11. Firefighters attacking a fire in a strip warehouse occupancy have two routes of entry, typically a swinging door and one or more overhead doors. Speed and ease of entry are important considerations, but firefighter safety is paramount. Consider that a swinging door in a strip warehouse may lead to a congested and poorly constructed office or sales area with literally a ton of storage overhead. A ceiling will block the view of a thermal imaging camera and prevent firefighters making entry from observing the type of roof construction, its condition, and the presence of overhead storage. Further, a serious fire in a strip warehouse requires the use of 212-inch handlines and portable master stream devices. These heavy streams, however, will not reach the fire if they are blocked by walls in an office. Forcing an overhead door gives firefighters access to a main aisle and the ability to bounce streams off the underside of the roof.


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Photo 12. Firefighters are entering an adjacent warehouse bay to check for fire extension. They gained access by cutting a triangle in the steel overhead sectional doors. Cutting a man-size opening in a sectional door built to withstand hurricane-force winds is no easy task. Consider that wind bracing on the inside of the door can make its overall thickness exceed five inches, which is beyond the maximum cutting depth of the 14-inch rotary saw. When possible, firefighters should try to access the latches mounted on the inside of the door, release them, and raise the door to provide the largest opening possible with a minimum of cutting.


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Most overhead sectional doors have sliding “L” bolts or latches mounted on the inside surface of the door. These latches are almost always mounted on the second section from the bottom. You can rapidly access the latches by cutting triangles in each end of the second section. Cut only the sheet metal skin; avoid the thick wind bracing, reach in, and release the latches. It is critical that any overhead door raised under fire conditions be supported in the open position with pike poles to prevent it from closing unexpectedly behind firefighters, trapping them inside the building.

This turned out to be a routine fire with no civilian or firefighter injuries. Knowledge of the hazards associated with fires in strip warehouses along with disciplined and effective firefighting operations kept this routine fire from becoming a tragedy.

BILL GUSTIN, a 33-year veteran of the fire service, is a captain with Miami-Dade (FL) Fire Rescue and lead instructor in his department’s officer training program. He began his fire service career in the Chicago area and teaches fire training programs in Florida and other states. He is a marine firefighting instructor and has taught fire tactics to ship crews and firefighters in Caribbean countries. He also teaches forcible entry tactics to fire departments and SWAT teams of local and federal law enforcement agencies. Gustin is an editorial advisory board member of Fire Engineering.

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