VENTILATING FLAT ROOFS
BY BOB PRESSLER
As the officer of the first-due ladder company, you await the report from the first engine. The engine is already on the air, having just gone in service from an ambulance assist run. The alarm received from the dispatch center is vague, reported as smoke in the area of Center and Third streets, no exact address. The area is in the older part of town, filled with three-story brick buildings with apartments over stores and one- and two-story commercial buildings.
The engine company arrives and reports: “Heavy smoke on Center Street; investigating further.” As you turn onto the block, the officer gives his second report: “We have a working fire at 315 Center Street, fire on the top floor of a three-story brick building. Engine 3 is leading off with a 134-inch handline.”
Because of the in-service preplanning program, you know that most buildings on that block are three-story brick, apartments over stores, and have flat roofs. The top-floor fire in a building with a flat roof indicates a need for immediate vertical ventilation. You turn to your crew and make assignments: “John, you and I are inside. Tom, stay with Steve (the chauffeur) and get the roof.” As you pull up in front of the building, the company is ready to go to work.
SIZE-UP
The roof team has several considerations as members start their size-up. Immediate concerns are the type, size, and construction of the fire building and adjoining structures. The building in the scenario above is a three-story structure of ordinary construction, approximately 20 feet wide and 50 feet deep. It is a mixed-occupancy building, with stores and apartments, as is common to many downtown areas across the country. It is attached on the exposure 2 (B) side by a similar building, but the building on the exposure 4 (D) side is only two stories high. The front of the fire building shows heavy smoke but no visible fire except for a glow toward the rear.
GAINING ACCESS TO ROOF
The roof team has three options to gain access to the roof: the adjoining building on the exposure 2 side; a rear fire escape, if present; or the aerial apparatus. Prefire planning and knowledge of building construction help in this decision.
The adjoining building. Smaller buildings of this type have only a scuttle cover on the roof that is accessed by a straight ladder located in a closet on the top floor. These ladders often are removed for security reasons; and if the ladders are present, they usually are blocked from use by items stored in the closet that do not fit in the apartments. Even if the ladder can be used, the firefighter who climbs it must then try to unlock any securing devices while his head is at the same level as the cockloft, which, depending on conditions in the fire building, may prevent him from seeing smoke, feeling heat, and remaining in the area.
Fire escapes. Rear fire escapes may or may not be present, depending on the number of apartments per floor and local building codes. However, the lack of visible fire in the front and the glow and smoke toward the rear indicate a fire in the rear. If the fire has vented out the rear windows, access to the roof via the rear fire escape ladder may be obstructed by fire.
Aerial apparatus. This is the best option for gaining access. Unless wires, trees, or obstructions are in front of the two three-story buildings, the aerial can be extended to the roof line of either building. If the front is free of obstructions, extend the aerial to the exposure building. This keeps the firefighters out of the smoke as they ascend to the roof. It also gives them a safe vantage point from which to observe the roof of the fire building.
From the exposure, the roof team should check for the presence of any shafts between the buildings. When crossing over to the fire building, the team should cross near the front of the building. This is normally a safer method than crossing at the rear because the fronts of the buildings are normally in line, whereas the rear building line may be staggered or open shafts may prevent you from crossing safely from roof to roof.
ON THE ROOF
Venting natural openings. Once on the roof of the fire building, the roof team must check the rear and sides (in this case, the exposure 4 side) for any trapped civilians. If any are found, the team should immediately notify the incident commander and the truck officer. As one firefighter remains to reassure the victim(s), the other firefighter should begin venting the skylight(s) and scuttle to try to alleviate the smoke condition on the top floor. If your department has lifesaving rope capabilities, begin such an operation immediately. At the same time, the inside team should also be attempting to reach the trapped occupants. If blocked by interior fire, consider access via an aerial or portable ladder or by breaching a wall between rooms or apartments.
When searching for civilians, also be on the lookout for any visible fire or smoke. When heavy smoke or fire is showing out the rear windows, notify the IC or truck company officer. Also bring to the IC`s attention any other features in the rear that are out of the ordinary, such as party balconies, rear setbacks, or an alley that may provide access for a truck company.
After the initial survey, the firefighters` attention should turn to opening up all the natural roof openings, including skylights and scuttles. Usually a large skylight is located over the stairway, and often smaller ones can be found over the bathroom and/or kitchen.
Take the skylight over the stairs first. Break one pane and then pause briefly. This gives any inside firefighters that may be on the staircase a few seconds to get out of the way or take cover. Then break the rest of the panes. Next, reach down with the handle end of a hook to probe for the presence of a draftstop or screen. Both devices, if in place, will stop the falling glass and reduce the effects of ventilation. Pushing down with the hook usually will dislodge a screen or draftstop.
Once you have completely vented the main skylight, look for other, smaller skylights. Also open them and check for screens or draftstops.
The roof team should then attempt to remove the scuttle over the interior ladder. If the door to this closet on the top floor is closed, removing the cover will not produce great quantities of smoke. Using the handle end of a hook, attempt to push the door open. Under no circumstances should you descend the ladder to open the door–you will be caught in a flue as the heat and smoke vent up the opening.
Horizontal ventilation. After venting all natural openings, the roof team should concentrate on assisting in horizontal ventilation unless fire conditions dictate opening up the roof itself.
If assisting in horizontal ventilation, members can reach over the roof with hooks to break glass or can use a rope to swing a tool into the windows. The rear fire escape also can be used for access for venting and possibly entering to help search for victims if the fire has been darkened down.
Cutting the roof. When confronted with a heavy body of fire on the top floor, you will probably need roof ventilation. The roof team must determine where to make the first vent hole and what size to make it. For fires in the rear of smaller buildings, place the vent hole to cover both rear rooms. Make it eight to 10 feet from the rear wall. A three-foot by three-foot (minimum) hole in this area should vent parts of both rear rooms and possibly part of the interior hallway in the apartment. The three-foot cut line is more manageable; cut the hole so you can enlarge it easily (see illustration above).
After cutting the hole, pull the boards and push down any ceilings below. If fire vents from the hole, try to enlarge the hole. If fire conditions prevent doing this, drop back toward the middle of the roof and start a second hole. The second hole should cover a large part of the interior hallway as well as parts of other rooms.
After cutting the hole, pulling boards, and pushing the ceiling, if no fire shows at the hole, use a different approach. Make a series of kerf cuts or inspection holes eight to 10 feet from the original hole toward the front. if no fire is found, the fire probably has not extended to the cockloft.
Larger buildings. Operations in larger buildings are more difficult. There is a larger perimeter to check and most often a bulkhead over the interior stair(s). Depending on the need for security, this door may be fastened with a hook and eye or possibly a padlock (although illegal). Forcing the door is necessary to relieve the built-up heat and smoke and also to check for any civilians who may have tried to flee to the roof.
After forcing the bulkhead door, if a heavy smoke condition is evident, firefighters on the roof should attempt to ventilate the skylight usually found on top of the bulkhead structure. This is a dangerous operation, as you have to climb up onto the structure to be able to break the glass. Make sure you always climb down the same way you climbed up because some bulkheads are situated along exterior walls–and climbing down the wrong side could lead to a fatal fall.
After venting the bulkhead and skylight, you can continue assisting in horizontal ventilation or proceed with cutting a vent hole.
Choosing a location for the original vent hole is also harder in a large building. Some of the factors to help you determine the correct location include fire or smoke venting from particular windows, bubbling tar, steam from a wet roof, and a radio message from interior companies.
Make the hole at least three feet by three feet to start and easily expandable. As in smaller buildings, make the hole eight to 10 feet back from the parapet wall. This vents the fire room and the interior hallway. When fire vents from the hole, the hole should be enlarged. If heavy fire is found in the cockloft, call for a second saw.
Make kerf cuts or inspection holes to determine the direction of fire travel. If heavy fire drives the company away from the original hole, cut a second hole in the direction of the fire spread. Be careful not to open vent holes past the advancing fire–doing so will spread the fire to that location.
Trench cuts. In large or multiwing buildings, if the fire is continuing to spread and is threatening the whole building, you may use a trench or strip cut. A trench cut is a labor-intensive and time-consuming operation that usually requires two saws to complete the cut in a timely manner.
When deciding to use a trench cut, use the building features to help you. Cut at the smallest width of roof, many times from bulkhead to parapet wall. Make the trench cut at least three feet wide, and properly protect it with a handline beneath it. With all ceilings down, the handline can protect against fire that is trying to pass the trench.
A common problem associated with using trench cuts is that many times the fire has already burned through the roof, so the roof team decides not to cut a main vent hole but starts a trench instead. Even though the fire has burned through the roof, the cockloft may not be fully vented. Sometimes the tar roof actually meets and drops over the cockloft opening, preventing fire and smoke from reaching the hole.
The other major problem is that the longer it takes the fire to burn through the roof, the farther the fire has spread laterally in the cockloft. The more heat and smoke a cockloft fire develops, the faster it spreads. As the fire burns through the roof, it may slow the spread but usually will not draw all the fire back to the burn-through. Because of this, do not start trench cuts until you have a main ventilation hole in place, even if the fire has burned through a section of roof. This main vent hole, if properly placed, will slow the advancing fire in the cockloft and will also buy you time to properly put a trench cut in place. If you have not already cut a main vent hole, the trench will become the main vent hole as the fire is drawn to this new source of oxygen.
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All roof operations are inherently dangerous. They are performed above the main body of fire and usually without the protection of a handline. It is imperative that firefighters be properly trained in power saw operations. Departments also must stay abreast of new construction in their response district. New lightweight truss construction is basically too dangerous to work on. Although some operations may be performed, if fire enters the truss loft or void, rapid fire spread is assured and collapse is imminent. Operations must be tailored to different buildings. Experience and training are musts.
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Although using adjoining buildings for roof access is usually quicker, unknown obstacles can sometimes limit movement from roof to roof. The use of chain link fences, some topped with razor wire, has gained in popularity. When confronted with chain link fences, it is easier to cut the supporting posts and drop the entire fence than to try to make an opening in the links themselves.
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When venting a corrugated metal roof, two series of cuts are normally required. The first series is only the roof covering, usually tar (and gravel) and an insulating material below the tar. The second series is made three to four inches inside the boundaries of the first cuts so that the blade can achieve the proper depth. Take care to avoid cutting through the trusses that support the roof. When trying to pull the cut sections, keep in mind that the metal roof is tack-welded to the trusses, making it difficult to remove the cut sections. (Photos by author.)
BOB PRESSLER, a 22-year veteran of the fire service, is a firefighter with Rescue Company No. 3 of the City of New York (NY) Fire Department. He created and produced the video Peaked-Roof Ventilation for the Fire Engineering video series “Bread and Butter” Operations. Pressler has an associate`s degree in fire protection engineering from Oklahoma State University, is a frequent instructor on a wide range of fire service topics, and is a member of a volunteer department.
