Marble installations, when done correctly, are a source of pride and beauty. Marble is a long-lasting finishing product; however, it requires proper maintenance to retain its good looks.
As marble continues to grow in popularity, it is very important that you, as a purchaser, are especially careful in your selection. Marble is imported from areas as far away as India, Israel and Turkey, and it is important to make the correct decisions.
Your first step is to find a qualified supply source where you can expect support for problems that may surface when your marble is delivered. Step two is selecting the type and color of marble you desire. Never select color from one sample piece; the tile is cut from a single block of marble and there will be shade variances. Be sure to take veining into account, especially when considering the layout. The veining of one tile may be in a fairly straight direction, while another’s may be offset. As an installer, you should expect that the pattern installation be decided in advance.
Should the tile have a honed finish, as recommended by the Marble Institute, or should it be a polished finish? The majority of marble installed today is polished. Of course, polished tile has a distinct look and will probably require more maintenance. Another factor to keep in mind is slip resistance, of which honed tile is the better provider.
Another concern is the “softness” of the tile; some softer tile is not recommended for use on the floor. The Marble Institute recommends an abrasion resistance of 10.
Once the choice is made, communication between the installer and end-user becomes of the utmost importance. Some of the problems that may occur after installation include discoloration, warping, a loss of vein material, hollow sounds and cracking. If the customer is aware of these possibilities ahead of time, it will save everyone involved a lot of time and money.
Discoloration can occur in “thin” (3/8-inch) marble. This may be caused by gray mortar or adhesive being used as the bonding agent. Gray mortar may be acceptable for darker-colored tile, but white mortar should be used under light-colored tile. I do not recommend the use of organic adhesive in any case.
There are certain marbles that are not stable and may curl from the moisture in Portland cement mortar or organic adhesive. Certain greens and blacks are in this category. If using or installing marble that is considered unstable, you will have to use a 100-percent solids epoxy or a polyurethane. Information on a stone’s stability and hardness is available from qualified mortar manufacturers and distributors.
Another potential installation problem is dusty tile. You may wish to wash this bond breaker off, or simply use your bonding mortar and mix it thoroughly on the back of the tile. Setting dusty tile into mortar may result in failure.
The preferred method to prevent cracking utilizes a cleavage membrane and the thick-bed method. However, I am certain the vast majority of residential installations are done with the thin-bed method. In any case, for interior installations, 80 percent coverage is required to prevent hollow sounds and to reduce the chance of edge cracking from foot traffic.
Make sure you understand the coverage requirements. Get the importer or producer of aggregate marble tile to tell you whether their product does or does not require 100 percent coverage. Do not give anyone a “Get out of jail” card by not following guidelines or collecting the necessary information.
The thickness of marble dictates the use of expansion joints as a vital part of a successful installation. The Tile Council of America has determined that interior areas should have expansion joints every 24 to 36 feet in each direction. If the tile is over a joint in the concrete, an expansion joint must be placed above the concrete joint.
I always seem to be talking about moisture, and rightfully so. It is important to test concrete on-grade for moisture. Excessive moisture can cause expansion in the marble veining and cause it to “pop” out. Marble is a beautiful and long-lasting part of your building. The proper marble and setting materials, combined with good floor prep practices, will provide the consumer with the installation they desire.