There are two types of tile material suitable for water immersion in freezing climates - glass and porcelain tile. Under no circumstance should any other tile material (ceramic, slate, marble, metallic, or other) be used on swimming pools, below or at the waterline. The reason for this is the porous properties of all other types of tile. Glass is extremely dense and will absorb no water at all. Porcelain is less dense and will absorb some water, but very little-an acceptable amount for pool tiling. Ceramic is more porous and less dense; stone such as slate and marble are much less dense and layered, as well as porous, which will result in guaranteed early failure, usually within 1-3 years from installation. However, not to worry, there are many slate-look porcelain tiles available for waterline that will last decades.
The other main factors in the lifespan of waterline tile are adequate preparation and cleaning prior to installation, and the quality of tile adhesive and grouts that are used. All of our tile is installed using polymer-modified, thin-set mortars that have a lifetime warranty, suitable for water immersion, and freeze resistant which are critical to ensure that tiles last decades. The tile is grouted with hydraulic, colourfast grout.