Fiberboard is made by mixing wood and other plant fibers with binding agents and compressing them into a sheet. Increasingly, fiberboard products are being made with post-consumer recycled fibers.
Fiberboard is also known as blackboard or grayboard, and is used as an insulative construction casing. As with plywood, fiberboard is used for wall sheathing and floors, and is used for both structural and nonstructural purposes.
Benefits of fiberboard are threefold: It has higher insulative properties than plywood, is more effective at sound reduction, and is the cheapest of the plywood alternatives.
Cement boards are panels created by combining Portland cement with fiberglass mesh material for reinforcement. These boards are most often used for floor work, specifically as a base for ceramic tile installation. Occasionally, they are also used for sheathing on the outside of a home or building, particularly structures which are to be coated with stucco. Because cement board doesn't offer structural integrity to a construction, buildings which have been encased with cement board require corner bracing.
Gypsum is a soft white or gray mineral made of hydrated calcium sulfate, and has been used in the building industry for many years. Gypsum panels have traditionally been compressed sheaths of gypsum encased in paper, though there are numerous types of gypsum panels, including gypsum core with glass mat facing and a hybrid of gypsum, cellulose and perlite with waterproof facing.
Like cement board, gypsum panels are used under stucco finishing as well as brick face.
Foil- or Paper-Faced Insulative Board
This type of insulative board is a very thin but strong sheathing panel with a thickness range of 0.078 to 0.137 inches. Despite the thinness of foil or paper-faced insulative board, this type of sheathing is considered structural, rendering corner bracing unnecessary. Another attractive feature of these panels is the ability to use sheaths that are much larger than some plywood sheaths, with some foil- or paper-faced insulative boards manufactured in sizes up to 80 inches by 16 feet.
Of all the varieties of alternative sheathing, foam sheathing is the most insulative. Each subvariety of foam sheathing has a different insulation rating, known as an R-value, which correlates with the formulation and thickness of the foam panel.
This type of sheathing is often made from extruded or expanded polystyrene, and polyisocyanurate. Because it is not considered structural, foam sheathing requires corner bracing.