Battles & Battles Tile sells and installs a great product called TI Proboard that
allows a deck to be tiled with no wood or backer underlayment. The product is
a metal alloy designed to stabilize the surface for a tile installation.
TI Proboard is attached directly to the joists, mortar is applied to the
channelled surface, and waterproofing can be applied to form a “roof” so that the
area under the deck is totally dry. You can even build a room underneath the
deck! After mortaring and applying the optional waterproofing, the deck is ready