Very simply, it’s nailed on. Fiber Cement siding and trim is installed by fastening the siding to the wall of the house using 2 different types of nails. Let’s get into the basic steps of a Fiber Cement siding installation. Fiber Cement Siding is installed by first removing the old siding and exposing the sheathing underneath, which is typically plywood. After a new waterproofing underlayment is applied over the sheathing, the Fiber Cement Trim and flashings are installed. That’s right, the trim goes on first. This is because Fiber Cement siding trim is not installed on top of the siding. Instead, the Fiber Cement trim is installed around windows, doors, and outside and inside corners. It is nailed to the plywood sheathing using Trim nails from a Trim nail gun, typically 16 Ga 2.5” Nails. The siding itself is then installed starting at the bottom of the wall. Each piece of plank or lap siding is installed in between the pieces of trim, so the end edge of the siding butts up to the vertical trim pieces. The lap siding is nailed along the top 1” section of the siding using a nail gun and 2” ring shank siding nail. The next piece or “course” of siding is then installed so that the bottom edge of the top piece covers the nails on the course below it. This technique is called blind nailing, and it provides a clean, attractive finish to the wall, where few or no exposed siding nail heads are visible. The small gap between the edge of the lap siding and vertical trim is then sealed with permanently flexible caulking to finish the installation.