You also have to make sure the top of the ladder can t slide when the rails rest against a wall.
A 12 foot extension ladder is placed against a wall.
The recommended angle for an extension ladder is 75 degrees from the horizontal 15 degrees from vertical.
The ladder is 13 ft long.
Make sure the ladder is vertical and the top is resting on an even surface.
If you do the math you will find that you will achieve this angle regardless of the length of the ladder by positioning the base of the ladder a distance from the wall equal to 25 of the ladder s overall length or 1 foot for every 4 feet of length.
A quick way to check this is to stand with your feet touching the ladder s base.
If you hold one arm forward you should be able to touch the ladder s rungs at shoulder height.
By following the 4 to 1 ladder rule the user ensures that the ladder is placed in such a way that maximizes balance and stability helping to prevent it from tipping backwards or to the sides.
Asked by wiki user 13 14 15.
Let the top of the ladder be y feet above the ground.
Providing a stable base is only half the battle.
Find the length of the ladder.
Example 11 a ladder is placed against a wall such that its foot is at a distance of 2 5 m from the wall and its top reaches a window 6 m above the ground.
Following this 4 to 1 ladder rule if a ladder is 20 feet off the ground the base needs to be 5 feet from the wall.
By completing the pythagorean triangle we know x y 13 169.
2x 2y dy.
Taking the wall as being along the y axis and the ground along the x axis let the coords of the top of the ladder be t 0 y and the foot of the ladder f x 0.
Angling the ladder to the left or right to reach a remote spot is asking for trouble.
The 4 to 1 rule prevents a ladder from being placed to close or too far away from the wall in which it is placed against.
Length of ladder i e.
Given distance from wall bc 2 5 m height of window ac 6m to find.
For example a 14 foot single or extension ladder cannot be used to work on a wall below a certain height because the user would be too far out from the wall.
Usually the lower portion of the wall can be reached from the ground up to a height of about 7 feet.
For example a 24 foot extension ladder will consist of two sections each 12 feet long but the maximum extended length will be 21 feet because the sections overlap by no less than 1 1 2 feet when the ladder is at maximum extension.
