So, let's go with 7 feet. For this 12-foot-high wall, you need a ladder that can be extended to 19-20 feet. Determine the likely range of heights you'll need.

A six-foot ladder is even better and it will also allow you to reach a 10-foot ceiling, and so on. With extension ladders, the base and upper sections must maintain some overlap for support.

Use a 6-foot ladder to reach a 10-foot ceiling, and so on. For an extension ladder, the base and upper sections must overlap. So, a 20-foot extension ladder is only good for about 17 feet.

A 35-foot extension, which usually is 20-foot bedded, works well to accomplish this, too—if it isn’t needed for upper floor access. The rear of the fire building can be difficult to access ...

When considering what length of ladder is best, you have to consider more than just the actual length, such as 8 feet or 20 feet. You also need to consider the maximum working length for extension ...