the builder of my house did not use any cement board under tile so i have many cracked tile in kitchen and baths. anything i can do to repair this without raising floor level due to handicap wife?
not using hardibacker is not a reason for having cracked tiles. the reason could be #1 poorly installed sub floor, #2 wrong installation materials, #3 people walking on the floor before the mortar/thinset has set up. what i would try to do is replace the broken tiles correctly (your cheapest route) make sure they're set up very well before grouting, grout them properly and over time, see if they crack again. if they do crack again then you can explore the sub floor option.
Yep --- cement board is not mandatory as MLBSF said.
One thing to consider --- many homes are built to minimum code in which case the floor structure at minimum code is only rated for carpet or sheet goods ( like vinyl ). They are too *bouncy* for ceramic tiles unless .. a) the floor sturcture has been strengthened -- b) built with closer spacing of joists.
Another factor that also can cause cracked tiles is * dry laid *. This where the thinset is applied to the floor and dries too quickly before the tiles are set in place --- and depending on your tile they may have not been back buttered if required.
Hard to say what can be done to repair the problem --- worse case the tiles need to come up --- floor structure strengthened --- uncoupling membrane installed -- new tiles properly laid overtop.
What they said above plus;
The first thing to do is to determine if the floor joisting is adequate for tiling. You need a deflection of L360 or greater for ceramic tiles, and L720 for natural stone tiles.
The bare minimum for the plywood layer is 5/8" with exterior glue plywood. Can you read the label printed on the plywood from the under side? 3/4" would be nicer.
While tile can be installed directly onto plywood, most pro's will not do it as there are too many things that can go wrong. An uncoupling membrane or 1/4" cbu will help a great deal. CBU adds no structural strength and no help in reducing the deflection. CBU manufacturers require the CBU be installed over a layer of thinset and held in place with screws or ring shanked nails.