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Extension Ladder Sizing

Extension Ladder Sizing

If you are getting ready to buy an extension ladder, you want the right height ladder to do the job. If you have a multiple story house - say one that is 2 and one half stories, a single extension ladder will not do all jobs. If you buy a ladder to reach to highest point on your house, it will be too long for the short jobs. Buy your short ladder first and see if you can't rent or borrow a tall ladder for the once-in-a-great-while tall jobs.

Extension ladders are usually sold in even foot increments, such as a 16, 20 , 24, etc. A 16 foot ladder consists of two 8 foot sections that are mated together. Because an extension ladder needs to overlap, its maximum length when extended is less than the length you thought you bought! The following table should help you see what I mean.

Extension Ladder Sizing Tables

Extension ladders should be 7 to 10 feet longer than the highest support or contact point, which may be the wall or roof line. This will allow enough length for proper setup, overlap of ladder sections, height restrictions of the highest standing level, and where appropriate, the extension of the ladder above the roof line. The highest standing level is four rungs down from the top.

The highest permitted standing level on a stepladder is two steps down from the top. A person standing higher may lose their balance and fall. A person’s maximum safe reaching height is approximately 4' higher than the height of the ladder. For example, a typical person can safely reach an 8' ceiling on a 4' ladder.


Highest Point the
Ladder will touch ++
16' 15' 9' max.
20' 19' 9' to 13'
24' 23' 13' to 17'
28' 27' 17' to 21'
32' 31' 21' to 25'
36' 34' 25' to 28'
40' 37' 28' to 31'

* Assumes a 5'6" person with a vertical 12" reach.
++ Support points for extension ladders reflect section overlap, ladder angle, or 3' extension above roof line.

Sizing Guide table and graphic courtesy of Werner Ladder Company

Related Articles: Ladder Safety Guidelines, Ladder Safety Tips, Ladder Manufacturers

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