Back To Basics: Ventilation Techniques For Flat Roofs

Although often overlooked, the position of the roof firefighter plays an important role in the outcome of the fire and serves as both the eyes and ears of the incident commander.

If there is fire in the cockloft and a defensive operation is needed, we can cut a trench. This is a time and manpower consuming operation and most times fires are extinguished by members pulling ceilings below and exposing fire for the hoseline. But when we are going to go to a trench operation we are giving up the building on the opposite side of the trench and withdrawing all operating members. This tactic is usually cut in larger H-type apartment buildings or taxpayers. A trench is cut after the main ventilation hole is cut and extended and inspection holes are made to monitor extension in the cockloft. A trench is cut at least 20 feet from the main vent hole and is cut from building wall to building wall.

To start the trench cut, beging by cutting two lines, three feet apart with cross cuts and knockouts every three feet. It is important to have inspection holes on both sides of the trench to monitor fire conditions in the cockloft. The trench should be cut in a narrow part of the building like using the throat section in the H-type, or incorporating a bulkhead structure or firewall for less cutting.

The trench is cut but not pulled and the ceilings below the trench are pulled and hoselines are positioned on the roof above and on the floor below the trench. When the fire reaches the inspection holes, the trench is pulled and the hoselines are operated to hold and extinguish the fire at the trench. If fire shows at the inspection holes behind the trench, another trench cut with extension holes would be needed, and the original trench abandoned.

Due to the new building materials and methods of construction, there are many different types of roofs out there. It is extremely important that the roof firefighter knows what type of roof he is operating on. These techniques are NOT to be used on the newer, lightweight construction which tend to fail in five to 10 minutes of exposure to fire, or when a truss or chord is compromised from cutting. For these lightweight types of buildings we will vent natural openings which are usually found at the ceiling levels on the exterior walls or a skylight or scuttle.

A good way to determine the construction of a commercial building where this lightweight construction may be found, is before entering the structure, push up a ceiling tile or pull a section of ceiling and examine the cockloft from the front door. This can be done using a eight or 10 foot pike pole and checking with a handlight or thermal imaging camera to determine if there is any fire in the cockloft and the type of roof construction. The roof firefighter can also determine this by cutting an inspection hole and if any metal from Q-decking or dust from Gypsum is present or any truss is seen, the incident commander should be notified and the roof should be vacated.


Charlie Hendry has been a member of the Hempstead, NY, Fire Department for 17 years and is a eight-year veteran of the FDNY. Recently promoted to Lieutenant, Charlie was previously assigned to Squad 288 in Queens. He has served as an instructor at the FDNY Fire Academy's Rescue Tech and HazMat Tech schools.