OPERATIONS ON PEAKED-ROOF STRUCTURES

BY BOB PRESSLER

Operations on peaked-roof structures usually are considered some of the most hazardous operations on the fireground. Peaked-roof operations combine many dangerous evolutions–gaining access to the roof area, moving on the roof surface, operating power tools or swinging hand tools (both of which require balancing acts), and conducting all operations above the fire area. Fire breaking through the roof decking can burn the firefighters operating in the immediate area or cause them to lose their balance and fall off the roof. The danger of roof failure–of the decking or the supporting assembly–is always present.

To make operations safer, proper training should cover types of peaked roofs and roof construction, ways to access and move on different roof areas, proper ventilation techniques including the power saw vs. the axe, and firefighter safety.

CONSTRUCTION

A roof assembly is made up of the following parts: rafters, decking, and covering.

Rafters. The rafter assembly might be constructed of sawn lumber, usually 16 inches on center, with the most common dimensions ranging from two by six inches to two by 10 inches. Newer houses may use lightweight truss assemblies, which now are very common. The largest piece of lumber found in these truss assemblies when used in single-family dwellings is often two- by four-inch. Spacing on these trusses also has been increased: 24 inches on center is common.

Also found, but not as common, are plank and beam structures. Plank and beam construction uses larger-dimension lumber (or timbers) as supporting members than the sawn lumber used in regular rafters. Purlins are beams set at right angles to provide additional support for the roof. Tongue and groove planks then are used to span these larger distances.

Decking. Found on top of the rafters, decking may be comprised of tongue and groove boards, plywood sheets, and “pulp” wood

or particleboard sheets. Older houses also may have just wooden shingles or shakes that are supported only by furring strips and may offer very little support under even a light fire condition.

Covering. The roof decking is normally covered with roofing paper and then finished using any of several types of coverings including as-phalt shingles, tile, slate, and wood shakes. Some older houses may even have a tin roof as the top or visible surface. Rubber membrane roofs also are found but normally are used on flat or nearly flat roofs.

TYPES OF PEAKED ROOFS

There are basically five types of peaked roofs and variations of the five types.

Gable-style roofs–the most common–are comprised of two sides that slope up from two bearing walls and meet at a ridge pole.

臀部有四个独立的方面,坡屋顶pward from four bearing walls.

Gambrel and mansard roofs have two slopes, with the lower slope steeper than the upper slope. The difference between the two is that a gambrel rises from two sides and a mansard rises from four sides.

Shed roofs slope up from one bearing wall to another, but the walls are different heights.

These roofs also come in a variety of pitches. The lower the pitch, the easier the roof will be to work on. The steeper the pitch, the more obvious the need to work from a roof ladder or an aerial device.

Roof pitch also impacts tool selection. Low pitches are suited to the use of power saws. The steeper the pitch, the harder it becomes to cut with a saw. A general rule of thumb is, if you cannot walk upright on a roof, leave the saw behind and use an axe. Even with roof ladders or aerial devices, the use of a saw is limited by ladder placement and the reach of the operator`s arm. Some of the newer, lightweight chain saws make operating from ladders easier; but if you are not proficient in their use, the operation still is extremely dangerous.

Roof pitches are identified by the rate of run vs. the rate of rise. If a roof is a four-inch on 12-inch, it will raise four inches for every 12 inches that it runs horizontally. This is a walkable roof–any steeper, and you cannot operate without some other support.

OPERATING HAZARDS

Regardless of the style or construction of a peaked roof, certain hazards are always present. Access to the roof area and movement on the roof expose members to a falling risk. Use utmost care when moving from a ground ladder to a roof deck or roof ladder. One wrong move can cause serious injury or death.

Once you reach the roof peak, you must know how to maneuver safely. On very steep roofs, trying to walk the ridge pole is dangerous. It is much safer to straddle the ridge pole and inch your way out to the proper position. While doing so, you may encounter chimneys or other firefighters blocking your movement. When bypassing a large chimney, grasp the chimney as close to the roof surface as possible and slide your body around. Many older chimneys are not structurally sound, and grabbing them near the top may result in the brickwork failing and your tumbling to the ground. If you encounter a small chimney or firefighter, pass by reaching around it/him and grabbing the ridge of the roof. The firefighter you are passing should maintain a firm grip on you by grabbing the back of your coat or SCBA to steady you.

Certain roof coverings also will impede your ability to walk or operate on a surface. Tile, slate, and some shingles do not provide a firm surface to work from and become slippery when wet. The tile or slate must be broken or removed whole to get to the roof decking for access for the ventilation opening. Take extreme care in removing the slate so the falling pieces will not strike other firefighters operating on the fireground.

If you lose your balance while operating on a peaked roof and start to slide down the surface, spread your body as flat as possible, with your arms and legs spread-eagle. This increases your “surface tension” on the roof and should slow you down. With your arms and legs spread wide, however, you increase the possibility of coming in contact with any rooftop hardware such as soil pipes and roof vents. As you reach the roof edge, try to hook your feet into the gutter. As a last resort, try to grab the gutter with your hands.

VENTING

决定在哪里打开一个通风孔the roof depends on where the main body of fire is located in the fire building. Proper size-up based on fire and smoke conditions, locations of exposures, and roof access will guide the incident commander in planning roof operations.

In private-dwelling fires, start roof operations immediately when fire has originated in the attic area or is expected to extend there. In houses with balloon-frame construction, fires that originate in the basement will rapidly extend up the outside walls and into the attic area, bypassing intermediate floors. When you encounter a heavy fire condition in the basement of these structures, begin roof operations. If interior forces are able to open up walls and voids on the lower floors, they may stop vertical spread. However, with this type of construction, fire spread is so rapid that completely stopping all extension is extremely difficult. Initial operations should include opening up any louvers or attic vents found at either end of the house.

Many newer or recently renovated houses have skylights. Prior to actually cutting the roof deck, try opening these skylights, if they are located over the fire area, to provide quicker ventilation. If the fire is located in the attic area or an area covered by the finished sides of the skylights (called returns), pull these side walls to vent this void space.

When you have to cut a hole in the roof for vertical ventilation in addition to the horizontal ventilation you have already performed, the size of the hole is determined by fire conditions, roof size and construction, and the roof team`s experience. Cut the hole as close to the ridge pole as possible. In lightweight truss houses, cutting as high up as possible is best. Cut the hole to cover as much horizontal area as possible. Cutting down the roof surface vents only that particular joist bay. By moving parallel to the ridge area, you will ensure more bay is exposed.

You normally can cut a hole approximately three feet along the ridge that extends down at least two feet without moving from a given position. When using a power saw, make a triangle cut. When using an axe, make the original cuts along the rafters. Once you start a hole, use the back of the axe to break through the roof boards unless the decking is plywood. If you encounter plywood and the roof is too steep to use a power saw, break through a small hole and enlarge it. Even if you open only a one-foot by one-foot hole, the fire will enlarge the hole when it reaches that hole.

You must perform roof operations very carefully. While perched on the peak of a house, you don`t want to swing an axe as hard as you can. Balance becomes very important. If you lose your balance while perched on the roof of a large 212-story frame building, you can fall almost 40 feet. Take short, accurate swings to maintain balance and still be able to open up a vent hole. Tools to take up to the roof include an axe, a six- to 10-foot hook, a power saw, and a utility rope. The length of the hook depends on the distance from the ridge pole to the ceiling you want to push down. Halligan tools are also popular; they can be used to break through roof board, pry up a cut roof section, or create a makeshift platform on which to rest one foot (just drive the point into the roof surface).

Always work toward a means of egress. Avoid cutting a hole that separates you from the ladder. Safe practices dictate ladder placement, preferably at opposite ends and opposite sides of the roof, for escape purposes.

To become proficient at peaked-roof operations requires proper training. Regional training facilities, roof simulators, and acquired buildings scheduled for demolition all can be used to enhance your training sessions and sharpen your skills. n

If a roof`s pitch is too steep to walk on, a roof ladder is required. Slide the ladder up the peak until you can engage the hooks at the ridge area. Use a roof ladder of the proper length. It should extend from the peak to over the outside wall. This way, the ladder is supported independently of the roof decking. Remember, newer lightweight truss construction has no ridge pole on which to hook a roof ladder. Collapse of the roof deck will tumble the unsupported ladder and firefighter into the attic area. (Photos by author.)

To maintain balance when operating on a peaked roof, firefighters should straddle the ridge pole. Extending your leg toward the side on which you will be operating will help you maintain your balance as you swing the axe.

当操作从一个空中或梯子巴克塔et, avoid working directly over the ventilation opening. Fire venting unexpectedly from the opening may strike the operating firefighters. Lower and/or retract the ladder so that operations will be off to one side or off of and above the end of the ladder.

The heavy smoke pushing from the attic windows and the entire length of the front wall indicates that this fire, which started on the first floor, is rapidly extending upward into the attic. Initiate roof operations as soon as possible. Steep slopes and heavy smoke require that a roof ladder be used and that the axe be used rather than a power saw due to limited visibility and maneuverability. Wear full protective clothing and SCBA.

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 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.