Avoiding Leaky Exterior Tile Decks by John Ogilvie Photo courtesy Golden Gate Enterprises MANY RESIDENTIAL AND LIGHT COMMERCIAL BUILDING OWNERS SEEM TO BELIEVE A TILE INSTALLATION IS WATERPROOF, AND FAIL TO PAY ENOUGH ATTENTION (OR MONEY) TO THE PROPER TREATMENT UNDERNEATH. The resulting leaks can occur undiscovered for years, eventually causing rot that requires major renovations. Not only does the structure need replacement work, but the tile application must also be removed to access it. The water most likely entered through cracked grout joints or on the perimeters. If the deck is in a cold climate, the moisture freezes, expands, and causes tiles to erupt. Still, a failure in the tile installation does not mean a failure in the waterproofing system. If the membrane is intact and performing its function of keeping the water out, replacing a cracked (or erupted) tile or grout joint is relatively easy and inexpensive. This article examines some of the common reasons for tile failure, the methods for building a deck to ensure it is ready for a floor finish, and the critical installation details for long-term durability and successful waterproofing. Installing tile on decks and balconies There are two distinct methods of installing tile in waterproof applications: thick-set (using a 38-mm [1 ½-in.] dry mud bed) and thin-set (using a 6.4-mm [¼-in.] acrylic-modified mortar). 1 Thick-set The thick-set method is more likely to be used where the tile is thick and irregular in order to achieve a flat walking surface. Installations (also known as ‘thick-bed’ and ‘mortar-bed’) are based on the traditional method of packing a mortar bed over a surface before installing the tile. The tile is adhered to the mortar bed either while it is ‘green’ (i.e. just beginning to dry) or after it has cured. 26 the construction specifier | february 2013 CS_Feb2013.indd 26 1/17/13 11:08:19 AM