I installed polished travertine marble over mud set walls in January 2009. Now it is almost May and the homeowner reports cracks that go right through the marble. I have never had something like this happen. I have been in the trade for over 13 years and never seen this. I have also talked to several 30 year plus guys who never heard of it either. The builder is trying to say my mortar bed failed. Not sure how that could happen since I have done everything exactly the same as I was taught and have done for years. The mortar bed was fully cured before I set the marble. Some of my friends think it is deflection because the floor joist possibly cannot support such a large amount of weight. Anyone out there with any advice!!! Im willing to replace the tiles but I feel that if there is something wrong with the structure that it will just do it again.