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Parts of pitched roofs indicate extent of flames during fires

October 23, 2014

Firefighters arriving at a blaze can draw clues as to the extent of the fire by looking at the building's roof, writes Jeff Johnson, a battalion chief at the Kansas City Fire Department in Missouri. Rain guards and flashings rising above the roof line could hint that the structure is about to collapse. Melting tar could also indicate that the roof is about to cave in, while turbine and fixed attic vents could show the extent of heat when smoke rises out of these fixtures, Johnson notes.  

Parts of pitched roofs indicate extent of flames during fires - Image 1

When arriving on scene at a fire building, it is easy to get tunnel vision regarding the smoke or fire that is showing. Fireground commanders must create a systematic size-up that will help ensure their crews are consistently evaluating “what you have, what you are doing, and what you need.” Sending personnel to the roof can make a difference in life safety and fire control. This article will look to the roof for helping determining your size-up. The obvious thing you look for on arrival is the smoke. Whether you arrive at a one-, two-, or three-story building, if smoke is showing, there is something to learn from looking at the pitched roof. First, is the smoke hanging around the eaves or is it rising high into the sky indicating heat with the smoke. High-heat smoke indicates a more developed fire, thus putting the occupants and firefighters in a more perilous position. If smoke is hanging (laminate) around the eaves, this indicates—at least from the exterior—that smoke with less heat has made its way to the upper floors. Next, you need to see what type of roofing material has been used to weatherize the structure.


The roofing material tells you several things about the roof. If heavy fire is underneath the roof decking, with asphalt shingles, you can have heavy, dark smoke coming from the roof line. With smaller fires, you can have significantly less smoke coming from the roof. The danger of asphalt shingles and lightweight truss construction is that the shingles can mask the roof failure that is about to occur. If the roofing material is much more substantial and heavy such as slate tiles or clay tiles, that roof substructure was required to be beefed up, and you will need additional personnel to accomplish the ventilation. With a heavier roofing material, the roof can collapse as early as a roof with lightweight construction, so keep evaluating the fire conditions either on the top floor or in the attic.  


Parts of pitched roofs indicate extent of flames during fires - Image 2

Dormers are invaluable for indicating the attic conditions. By looking into a dormer, you can typically see if there is active fire or smoke inside the attic. The dormers can also be used to help vent the heat and smoke. Another roofing indicator is located on three sides of the roof, where you have normal pitched ridge lines, and on the fourth side, where you find a shorten ridge line to a flat roof. This can indicate a section on the roof where heating, ventilation, and air-conditioning units can be placed, adding additional weight to the roof structure. Next, I will look at roof features such as skylights, pipe vents, and chimneys. You can learn a lot about how the roof is holding up during the fire. On arrival, a quick glance across the roof line helps you see if there are any skylights. With a working fire that requires ventilation, skylights are an easy opening. You must remember that when taking out a skylight, you can find a dust guard that is either clear plastic or a screening material for UV protection. This material needs to be removed to make the skylight vent effective. Next, look for rain guards and flashing to see if it is mounted flush with the roofing materials. If you take a quick glance, about 10 minutes into the response, at those rain guards and flashings and you see they are now raised above the roof line, this indicates that the roof is coming down. Tar that is used to waterproof the roofing around pipe chases, rain guards, skylights, flashing, and chimneys will begin to melt at 130°F; melting tar indicates that heat is accumulating in that area. For the safety of firefighters operating on the fireground, you have to watch for the chimney pulling away from the roof. Additionally, you must watch for the roof pulling away from the chimney (similar to the rain guards and flashing) because it also indicates that the roof is coming down.  


One type of vent on the roof is the turbine attic vent; you can get instant information on the fire depending on how fast these vents are spinning. I have seen many advanced fires in wood frame structures showing heavy smoke from the roof line. In these fires, the turbine vents were spinning as fast as you can imagine, which indicated high heat in the attic that needed to be vented. If the turbine vents are not spinning, you will have little to no heat in the attic space at that time. It must be said that if you have windy conditions, these turbines are less reliable, but still look for the smoke. Fixed attic vents will allow the easy flow of smoke, so any smoke condition with heat greater than the outside temperatures will rise out of these vents easily. Sending personnel to the roof can be a difficult decision based on the fire and smoke conditions, the pitch of the roof, the roofing materials, your personnel, and the equipment. However, it is an invaluable operation that you must consider. You may not have to ventilate the roofs at fires that are not located on the top floor or fires that consist of contents only; you may be able to remove the smoke using horizontal ventilation on the floor above the fire. An obvious change to this notion would be fire that is extending through pipe chases and the walls into the attic space. If you have fire on the top floor or in the attic space, then roof personnel may be there for an extended time performing ventilation and overhaul.  


Firefighters have to train for operations on roofs to be effective at these incidents. This training should include the following tactics and information:

  • Roof cutting techniques and equipment.
  • Identifying when roof conditions are becoming untenable.
  • Evacuation procedures.
  • Knowing to climb to the ridge line—not down to where they can fall off the roof—should they ever become disoriented while performing roof operations.
  • Ensuring ground ladders are three to five rungs above the roof line to help firefighters identify ways off the roof when ordered to evacuate.
  • Taking the correct tools up to the roof the first time to affect timely ventilation, which will then allow firefighters to get off the roof before conditions become too unstable. Roof ladders, pike poles, saws, flashlights, and self-contained breathing apparatus are minimums to operate in perilous situations above the fire.

The best training opportunity you have involves the roofs in your districts. To become more effective at ventilating residential pitched roofs, you must have practical experiences. Doing site visits at new construction and older pitched roofs can help firefighters when it comes time to open a pitched roof. Building a training prop is fairly inexpensive, while getting hands-on practical evolution will further reinforce pitched roof operations. Lastly, let us look at roofs during defensive operations. When using aerial ladders and towers during defensive operations, you have to remember what roofs are designed to do: shed water away from the structure! I have been at incidents where towers and ladders are set up and flowing water on the roof of a defensive fire, but they are having no effect on the fire. If the fire is through the roof, then, obviously, use those streams through the roof. However, if the fire has not burned through the roof, lower the master streams to exterior windows and openings to flow water directly into the fire from positions out of the collapse zone. When performing size-ups, use what the companies and the building are telling us. The roof is just one critical piece of the building from which you can gather information. Don’t forget to look up when performing your size-up.


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