Among other reasons, chances are that your marble floor tiles are not exactly square and using grout makes up for the small differences. You can have very narrow joints that are nearly imperceptable. Google search marble without grout and you’ll find lots of good reasons not to.
- Rhoda Fry
http://www.billfryconstruction.com/I’ve used Marble on two 1500 square foot basements and the owner didn’t want any grout joints, Im living proof it can be done, but it is very difficult to get perfect. I used 12x12 peices of marble, getting them perfectly flush was tough.
Thermal expansion and movement of the substrate will cause stress in the tiles. These stresses will be exerted on the tiles, as they push upon each other.
The result will be that tiles crack, buckle and come loose.
There are published standards for the installation of stone tiles. Google Marble Institute of America (MIOA) and the Tile Council of North America (TCNA). They both have published installation guidelines and manuals that have become the “bibles” for installation practices.
The TCNA Manual address crack control (cleavage) membranes, installation practices, cure times, movement joints, substrate construction & acceptable flexation of floors. ANSI (American National Standards Institute) has also established installation practices for stone and tile floors, which have been adopted by the IBC (International Building Code).