In my field of work I have seen many tile floors fail due to improper subfloors and wrong glues used during installations. Most tile floors when finished always look great unless the work was done half fast. What you dont know is what was done before and during the installation of the tile. Subflooring is the most important part for the longevity of a floor. All ceramic tile companies recommend a minimum of 1 1/4" subflooring before any tile is set. Most all of homes are built with 3/4" plywood flooring through out the house so an extra 1/2" where ceramic tile is to be applied is necessary wheather you use plywood or cementboard. Since ceramic tile, like concrete, is a solid product that does not do well under any movement is very likely to crack if the proper steps are not taken. What we do at WMB Construction is make sure the original subflooring is properly secured to the floor joists using 2 1/2" screws.(screws always hold better that nails that builders use during new construction.) Next we install 1/2" cement board(Perma Base) over original subfloor setting the cement board in Sturdi-Flex adhesive and using 1 5/8" screws every 3" to secure the cement board down. Now tile is ready to be set on top of a subfloor that is completely indestructable. Some might say my methods are a bit over the top but a little extra material and labor is well worth a great installation so that I can sleep at night
