If you need to work at height, then using an extension ladder is the obvious choice. However, using an extension ladder is not as simple as it first appears. To ensure you are safe and that you have chosen the right ladder for the job, you need to work out the height of the ladder – not only does it need to extend as far as your destination (a rooftop, for instance), but it needs to exceed it.
This is due to safety reasons. You should never hold higher than three or four rungs down from the top of an extension ladder because they will become unbalanced. Instead, you need to position the end of the ladder above the roof, to ensure safe passage onto it.
What’s more, the extension ladder won’t be stood vertically, so you also need to work out how much it will slant.
To help, this is how extension ladders should be measured:
The length of each section
Extension ladders differ from conventional ladders (such as step ladders) because they have separate extendable sections. To make your life considerably easier, you could measure each of these sections, to work out the extended length.
This is especially useful if you are operating in a tight space and don’t have the necessary room to extend the ladder fully. As long as the sections are equal, you should be able to work out the entire ladder length from one section.
Of course, this will not necessarily be the case with custom versions of extension ladders, such as a Roof Access Platform.
How to measure the full length
However, measuring the individual sections of a ladder only provides an approximate estimate of how long the ladder is. This is because of the overlap of ladder sections which essentially shortens the available length of each individual section.
To find out the exact length, you’re going to have to do it the old-fashioned way. Pull out the full extension of the ladder, then measure it with a tape measure.
A ladder isn’t positioned at vertical
As mentioned above, extension ladders aren’t positioned fully vertically when standing.
When it is resting against a wall or roof line, the ladder should be set at 75 degrees, for the length for proper setup. The exact maths will vary, but if your ladder was four metres long, then it might only be three high when leaning against a support or contact point.
Keep basic safety advice in mind
You should always keep basic safety advice in mind when working out how tall a ladder you will need.
For example, you need to make sure that the highest standing level is four rungs before the highest support or contact point.
The reason for this is that it isn’t safe reaching onto a rooftop from the highest three or four rungs. It could cause the ladder to slip or become unbalanced.
Therefore, you will typically need a ladder four to ten feet longer than the highest contact area.
What’s more, an average person’s safest reaching point is four feet, which means you may need ladder sections height restrictions if the person can’t reach. This is particularly important at the top of the ladder, so you may have to implement restrictions for the highest section.