There are two options when it comes to your tile installation project’s underlayment. Traditional cement board backerboard comes in ¼” and ½” thick boards that are 3’x5’ and 4’x8’; quarter inch is used for floors and counter tops, and half inch is used for walls and ceilings. Alternatively, you can use Wedi board, comes in the same size and thickness but is more commonly used for wet areas. Its waterproofing capacity is far superior to the traditional backerboard — while backerboard doesn’t mold or mildew, it does wick water, which means the boards that the backerboard is screwed to can mold and rot when moisture gets to them. Traditional backerboard has its place, but we do not recommend it for use in showers, tub surrounds, decks, and steam-rooms. When it’s wet, go for Wedi!