You could always borrow an extension ladder from cousin Ed or neighbor Judy when you need one. But having one handy means you can plunge into a lot of outdoor jobs you might otherwise put off. Here’s some help in choosing one.
If you have a flat roof or a hip roof your ladder should reach to your eaves, and if you have gable ends, you’ll need to get to the peak. (You may also want to consider chimney height.)
But don’t just transfer this distance to the ladder; keep a few things in mind. The two sections of an extension ladder need to overlap by at least 3 feet for strength, so a 20-foot extension ladder with two 10-foot sections only gives you 17 feet of effective height. As well, your ladder should extend about three feet beyond the roof’s edge. And the base of the ladder needs to be away from the wall: 1/4 of the height of the house.
Since ladders are usually sold in four-foot increments, that means you’ll need a 28 foot ladder for a 20-foot height.
And that brings us to materials. Most ladders are made of either wood or aluminum, with aluminum the choice of most homeowners. Wood is resilient and stable and won’t conduct electricity. But it’s much heavier than aluminum, which means long ladders can be tough to set up by yourself.
Aluminum ladders have other advantages. You can store them outside with no protection, and the flat rungs are easier on your feet.
Then there’s strength. Naturally it varies depending on the ladder material, but you can determine whether the ladder’s right for you by checking the duty rating. Type III will hold 200 pounds per rung, type II 225, type I 250, and type IA 300.