By Mark van der Feyst
A big part of truck company operations is ladders, especially ground ladders. Every fire apparatus will be equipped with at least two ground ladders: a straight single-roof ladder and an extension ladder. This is mandated by National Fire Protection Association (NFPA) 1931, Standard for Manufacturer’s Design of Fire Department Ground Ladders, for apparatus specifications. NFPA 1931 details what is required of ground ladders and how they are to be constructed. These standards are not interesting reading material, but they do contain some important information that we need to know as part of the basics, such as the following:
- The heat sensor labels that are found on the inside of the ladder beam are preset for 300°F.
- An attic ladder will be no longer than 16 feet.
- Minimum distance inside between beams for single ladders shall be 16 inches.
- Minimum distance between beams for an attic ladder shall be no less than 7½ inches.
All ground ladders are tested to ensure that they meet the NFPA 1931 standard. Most of us have never witnessed these tests being conducted, but they are intrusive and designed to test the extreme limits of the ground ladder.
In photo 1, we can see a ground ladder undergoing the Horizontal Bending Test. In this test, a load of 750 pounds is applied to the middle of the ladder. Notice that the ground ladder is fully extended; it is supported by two stands at least six inches from each end of the ladder. The test uses 750 pounds for weight because NFPA 1931 requires that all combination, single, and roof ladders as well as extension ladders must have a duty rating of 750 pounds when raised at a 75° angle.
(1) Photos by author.
Any test being conducted on a ladder must maintain a five-minute time limit. Notice how the ladder is bending under the test weight. There is probably a one-foot deflection occurring under these extreme weight limits. But are these extreme weight limits? If we were to use a ground ladder to rescue a civilian, there is a good chance that the ladder will endure some extreme weight.
The average weight of a firefighter fully donned with personal protective equipment is 300 pounds. This is a figure that the NFPA uses to assess firefighter activity weight for any operation. One firefighter on a ground ladder trying to rescue a civilian who may weigh as much as 300 pounds is now adding 600 pounds of weight onto the ladder. Depending on the behavior of the civilian, the ground ladder will bounce as they descend. Why do we need to know this? It is to build up our faith and trust of the ground ladder. It is designed to work under stressful situations and has proved itself to be a very effective tool on many occasions.
As part of our basics, we need to know the lengths of our ladders that we carry on our fire apparatus because when it comes time to ladder a second-story window, we want to pull off the right ladder the first time and raise it to the correct height the first time. Nothing looks worse than watching two firefighters raising and lowering a ground ladder and trying to select the proper height. If we know our ladder lengths, the average distances between floors, the height of the window sills from the floor, the distance between rungs, and how much a ladder tip will drop when we pull the base out and away from the wall, we will be able to estimate correctly the exact height we should raise the ladder the first time.
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In photo 2, we can see three different ladders being used to access different windows. Each one is accessing a different level of the building. We have a 12-foot ladder accessing the second story, a 24-foot extension ladder accessing the third story, and a 35-foot ladder accessing the fourth story.
Ladder math is a good tool to use when trying to determine to what height a ladder should be raised and which ladder to choose for the job. We know that in a typical structure, the height between floors will be 10 feet. The window sill will be around three feet from the floor. This gives us a total height of 13 feet to reach. If we grab a 14-foot roof ladder, will it reach the window sill? Yes. When moved away from the wall, a ladder will drop one foot for every four feet of horizontal movement.
When a 14-foot roof ladder is moved away from the wall to the correct climbing angle, it will have a vertical height of 13 feet. If we had a 12-foot roof ladder, it would also work; we may be about 18 inches below the window sill, but it will still allow us to gain access or rescue a civilian.
Our extension ladders are usually 24 feet. The bed of the 24-foot ladder measures 14 feet. Each rung on the ladder is about one foot apart. When we extend the fly section of the ladder, we need to count the number of clicks from the dogs to raise the ladder to the correct height. A 24-foot ladder fully extended will measure 24 feet. We can then theoretically reach a third-story window with a 24-foot ladder that has a vertical height of 23 feet from ladder tip to the ground. We need to consider other factors such as raised basements and sloping surfaces; this will add to our total height that we need to reach.
The best way to know the limitations of your ground ladders is to practice with them. Use existing buildings in your area and ladder the windows on different stories. Ask the crew to estimate how high the ladder must be raised to reach certain windows. By doing this, your crew can practice estimating ladder heights, and they will know exactly the limitations of each ladder. They will also know which ladders to use to reach certain windows if they get called to that building one day for a fire.
Mark van der Feyst has been in the fire service since 1999 and is a full-time firefighter in Ontario, Canada. He is an international instructor teaching in Canada, the United States, and India, and at FDIC. He is a local level suppression instructor for the Pennsylvania State Fire Academy and an instructor for the Justice Institute of British Columbia. He is also the lead author of Residential Fire Rescue (Pennwell).
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