Longer-length sidings are generally extended versions of standard-size siding products. Standard sidings are usually 12 feet to 12-1/2 feet long. With standard siding panels, seams appear every two to three feet. Longer length sidings are typically offered in 16, 20 and 25 foot ranges. 
The primary benefit of longer-length siding panels is that it reduces the number of seams on the wall. Siding seams can be an aesthetic objection to vinyl siding. With longer-length panels, there are fewer seams. For example, on a 20-foot wall, a 16-foot panel creates 35 percent fewer seams than a standard-size panel, and a 20-foot panel reduces seams by 100 percent. In short, the longer the panel, the fewer seams.
Longer lengths can also reduce the amount of time required to install siding since more area can be covered with fewer panels. Most longer-length sidings are designed to be installed with their standard-size counterparts so that various sizes can be used together on a project for efficient utilization of material.
CertainTeed offers our CedarBoards XL, our insulated siding in 16-foot-8-inch lengths and Monogram 46L is available in 16-foot-8-inches in D4 Clapboard, 16 feet in D5 Dutch lap, as well as 20-foot lengths in both D4 Clapboard and D5 Dutch lap.
