Marble tile can be installed over existing ceramic tile provided the ceramic tile is in good condition and has a relatively flat surface. One problem when tiling over existing flooring is caused when parts of the hidden floor come loose. If the ceramic tile is not firmly adhered to the sub-floor it will come up and cause the marble tile on top of it to come loose as well. Check the floor carefully for damage before you decide to install marble over ceramic tile.
Things You'll Need
Ceramic tile adhesive
Clean the ceramic tile thoroughly to remove any dirt or residue that may have accumulated on the floor.
Check the floor for any loose tiles and glue them down with ceramic tile adhesive.
Use a notched trowel to apply a layer of thinset mortar to the floor. Work in sections and only spread as much mortar as you can cover with tile before the mortar dries.
Press the marble tiles into the thinset mortar. Leave a 1/16-inch space between each tile to create a very thin grout line. Continue to spread mortar and lay the marble tiles until you have covered the entire floor. Cut the marble tiles to fit as necessary with a wet saw.
Apply marble sealer to the tiles following the directions for the sealer you chose. Sealing the tiles now will make grouting easier as the grout will be easier to remove from the face of the marble tiles.
Prepare grout according to the directions on the package and spread the grout across the tile with a rubber float. Move the grout around to fill the grout lines and then use a damp sponge to wipe away excess grout from the surface of the marble tiles.
Purchase white thinset mortar when you are installing white marble, as gray thinset mortar may be visible through the surface of the white marble.