In many high-end custom homes, the marble floor tile is the same material used on the shower and bathroom walls; the material is interchangeable with both horizontal and vertical surface areas. With the proper substrate and employing the correct setting techniques, marble floor tile is not too heavy for walls.
A sound, proper substrate is absolutely necessary for wall installation of heavy marble floor tile. A lath-and-mortar substrate is the strongest and soundest. A cement backerboard substrate is also adequate but the backerboard must be 1/2 or 5/8 inch thick. A 1/4-inch backerboard does not provide enough strength for installing large marble wall tile.
Polymer-modified thin-set mortar is the only setting material that you should use for a marble floor tile wall application. Polymer-modified thinset has special bonding agents and glues in it that provide an extra bond and "bite" to the ball -- this is especially important given the weight of the stone. Expert tile setters also use a rubber mallet to position the marble tile and comb both the substrate and piece by applying thin-set mortar with a v-notch trowel.
Thick, heavy pieces of marble floor tile -- especially lathered-up with thin-set mortar -- are extremely heavy. Experienced tile setters install heavy marble tiles on walls with the help of an associate or journeyman. Suction cups -- sold at tile supply warehouses -- come in handy for handling heavy pieces. Also, it is of paramount importance that the pieces of marble floor tile do not have any cracks in the body of the stone. Called "dry pockets" in the tile and stone trade, small cracks in the stone crack a piece while lifting it.
In some cases, building code requires the use of special fasteners called "mechanical fasteners" on vertical areas to install heavy marble on walls. This aspect of building code typically only applies to extremely high heights. Nevertheless, it is a good idea to check local code in your area.