When cement backerboard became available in the early 1970s, it became a popular substrate for tile installations because of its imperviousness to water. Although it remains popular, backerboards made of other materials have since come on the market. In this article, senior editor Martin Holladay looks at each of them in turn. Cement is still the leader in water resistance but is heavier than other materials and shouldn’t be used on floors because of its brittleness. Polystyrene backerboard consists of panels of polystyrene (either EPS or XPS) covered in fiberglass and polymer resin. Light in weight but surprisingly strong, it is available in more sizes and thicknesses than other backerboards. It also costs more. Fiber-cement backerboard is similar in many ways to cement backerboard, although it weighs less and is less brittle. Its smooth surface allows it to be finished with paint or wallpaper. Gypsum-core backerboard is lighter than both cement backerboard and fiber-cement backerboard, and it handles much like drywall. Unlike drywall, however, it has a waterproof facing; still, most gypsum-core backerboards should not be used in areas that experience daily wetting.