Nailing clapboard siding: top, bottom, or both?

Q: The builder of my house nailed the top and the bottom of each cedar clapboard. Won’t this cause the boards to split?

A: Associate editor Daniel S. Morrison replies: Normally, you nail either the top of the siding or the bottom of the siding, but not both. The main reason for nailing the top of the board is to hide the fasteners, but nailing the tops leaves the bottoms a little loose, giving bugs possible entry points. Nailing the bottoms allows for easy removal and secures the top of the lower board. Nailing both top and bottom is unnecessary and, in fact, may cause splitting, as you point out. When nailing the bottoms of clapboards, make sure to keep the nail high enough from the bottom to clear the top of the previous siding course.