Tile needs to be installed on a backer board to keep the assembly stiff, otherwise the assembly will flex at the grout joints, allowing water to seep behind the tile and rot the substructure. Here's how to choose the best tile backer board for your project.
Some types can be used outside (check brand specifications).
Ideal tile-setting surface for thin-set mortars.
Needs at least 1-1/4 in. of edge support for proper fastening.
Should be backed with a plastic or other waterproof membrane to protect wood framing, because it isn’t waterproof.
Fiber cement board is a variation of cement board that’s made from compressed cement and sand, reinforced with wood fibers throughout. Its installation procedures and durability are similar to those for cement board, but be sure to read its product specification sheet for specific limitations. It’s only available in 1/4-in. thick sizes.
Glass mat gypsum board works well in damp areas, including tub surrounds, but not in areas that may be continuously wet or damp. The sheets are made from water-resistant silicone-treated gypsum, reinforced on both sides by fiberglass mats. The tile side is sealed with a waterproof coating. It’s typically available in 1/2-in. thick, 4 x 5-ft. sheets, but tile dealers carry other sizes, including 1/4-in. thick sheets.
Waterproof skin; doesn’t need an additional moisture barrier.
Lighter in weight than cement board.
Easier to cut and fasten than cement board.
Will soften if water seeps through joints or gets behind the waterproof surface.
Can’t support all types of floor tile (see product specification sheet).
Fiberglass mats irritate bare skin. Wear long sleeves, gloves, goggles and a dust mask when cutting and handling them.
Water-resistant drywall is a good backer board choice behind sinks and other places where occasional splashing and high humidity could affect regular drywall. The sheets are made from a water-repellent gypsum core covered by water-resistant paper. Like regular drywall, it’s found at most home centers in 1/2-in. thick, 4 x 8-ft. sheets.
A good base for paint, wallpaper and tile in occasionally damp areas like kitchens and bathrooms.
Inexpensive—about a fifth the price of the other types of tile backer board.
Not suitable as a tile backer around tubs and showers.