Ceramic tile, more than any other form of flooring, requires the proper subfloor system and setting materials. A double subfloor system with the total thickness of 1-1/4 in., over floor joists 16 in. on center is required. The top subfloor layer should be exterior grade plywood or an underlayment specifically designed for ceramic tile installation like cementous backerboard.
Special setting materials are available which will allow ceramic tile installations over existing floors that are solid and already meet the above requirements. Failure to provide a sturdy base can cause grout to crack and release or tile to crack.
The quality of raw materials, the firing process, and the sophistication of glazing applications that create realism will determine the quality of the finished product. These quality differences are often reflected in the price.
Floor tiles are rated for glaze wear and slip resistance, which are important factors to consider. Glaze ratings should exceed 3 for residential applications with the exception of bath areas that can use tiles rated 2. Tiles with a slip resistant rating of 0.5 or better should work well in most indoor residential applications.
Use caution when selecting tile for installations outdoors. Unglazed quarry tiles, tiles with heavily textured surfaces, or porcelain paver tiles, all with slip resistant ratings of 0.6 or greater are possibilities. They must also be frost resistant.