QUESTION

I had problems with my bathroom contractor, and I had to let them go and then I left town for three months. My real Carrara marble Tile has been stored outside for three months under sheets and blankets in Los Angeles California. It has been pretty dry, however the temperatures have gotten up to 105 at certain times. It isn’t stained and looks perfect.

The tile guy arrived today and said that the marble is no good and could crack. He wants me to buy all new pieces. This will cost me thousands. Is he right? He also said that the floor tile Has to have sand in the grout for the floor to be even. Is that true? Please help.

ANSWER

ANSWER - I don't know why someone would say the marble could crack, if it isn't already cracked.  I don't know what evidence there could be to suggest the marble could crack if it isn't already cracked.

Normally it is moisture that can be damaging to a marble that is left out in the elements.  It is possible that excessive heat and moisture could cause a stone to warp if it is being subjected to disproportionate heat or moisture, or that it cools or dries disproportionately after being subjected to heat or moisture respectively.   If that were the case, then you should be able to see that the marble is warped.

If you put two pieces of marble together face to face or back to back, and there are gaps because the marble tile doesn't sit flat, that could be problematic.  It is possible to install the marble in a way to help compensate for warpage; if the warpage isn't too extreme.  It should not have more than 1/32" warpage to meet the standards.

If the marble is not stained or excessively warped or damaged in some other way, then there isn't any reason why it can't be installed and perform well if it is installed correctly.

Cementitious grout comes in two forms; either sanded or non-sanded.  You can only use non-sanded grout in grout joints that are 1/16" wide because the sanded grout won't fit into that small of a joint. Although you can use non-sanded grout in grout joints up to 1/8" wide. If you use it in wider grout joints then it will have a tenancy to crack.

A sanded grout can be used in grout joints that are 1/8" wide or up to 1/2" wide.  There are special grouts for wider grout joints.

The MIA standards recommends a minimum 1/8" wide grout joint, but never less than 1/16" wide for stones that don't have variations in size.  Sanded grout is more resistant to cracking, so I always use sanded grout in grout joints that are 1/8" wide.