A large walk-behind scrubber can be used to clean both stone and tile surfaces. These machines can also be equipped with diamonds to hone stone floors. They are also good for grout cleanup on a newly installed floor.
I recently met a ceramic tile contractor at a trade show and the subject of installing stone tile came up. He told me that he did not understand why there was such a big deal about setting stone. " After all, it's the same as setting ceramic tile," he said. He could not have been more wrong. While there are similarities in setting stone and ceramic tile, there are major differences that, if the setting mechanic is not aware of, could lead to disaster. What can go wrong, you might ask? Complete failure of bond, sometimes called loss of bond or delamination, is a common problem caused by improper setting material and technique. Discoloration and/or staining due to the wrong setting material. Efflorescence appearing, caused by over use of water. Mysterious scratching caused by sanded grout. Shall I go on? The problems can be numerous, and can be avoided if you know the differences. Let's take a look at the differences in setting stone and ceramic tile and some of the problems associated with improper technique and setting material selection.



Polishing of stone flooring with a floor machine. Care must be taken with stone not to scratch the floor, whereas ceramic tile will generally not be harmed with standard pads.

The Tile:

There are many differences between ceramic tile and stone tile. Ceramic is a man-made product, and is generally homogeneous in construction. In other words, each and every tile has the identical composition, and therefore has predictable qualities. On the other hand, stone tile is a product of nature and can differ in composition from tile to tile and therefore has unpredictable qualities.

Ceramic tile is generally non-porous to slightly porous, resulting in a very low absorbency. Stone tile can be very absorbent, and for this reason can cause several different setting problems.

Ceramic tile is generally lightweight and relatively thin. Stone tile ranges from 3/8-inch thick to as much as 1 1/4-inches thick and can be very heavy. A 12-inch-square stone tile can weight as much as 10 pounds or more.

The back of a ceramic tile is cast with many different corrugations designed to provide the proper bonding of the tile to the setting bed. The back of a stone tile has no corrugation, and is generally saw cut or smoothed.

Ceramic tile is generally resistant to acids. Certain stone tile, marble for example, is very sensitive to acids. It is important to know the differences in the material you are working with. This will avoid many problems during and after the job.



A hand machine as pictured here should never be used on ceramic tile, but can work well for stone surfaces.

Preparation:

A good stone or tile setter knows that preparation of the surface to which the tile will adhere is the key to a trouble-free installation. This is where setting stone tile and ceramic tile have common ground. But there are some differences. Due to the porosity of stone tile, it is important that the substrate to which the setting bed is to adhere be free of materials, both organic and inorganic, that might cause staining of the tile. Green plywood that contains sap can bleed through. The nails that attach the plywood to the floor can rust and bleed through the surface of the stone. Will the subfloor support the weight of the stone tile? If stone tile is set on a floor joist, there is a possibility that if any deflection is encountered, the stone tile can develop what is known as compression cracks. Compression cracks appear as fine, hairline cracks below the surface of the tile. If deflection is suspected, it is recommended to install a slip sheet to absorb this deflection.

When preparing the subfloor, use some common sense and be aware what can possibly go wrong. Knowing the properties of stone and ceramic and their differences can save a lot of headaches.



Students at the National Training Center for Stone and Masonry Trades participating in a hands-on seminar on stone installation and fabrication.

Tools Required:

When setting stone tile, you can throw away your tile nippers and tile cutters. Stone cannot be trimmed and cut like ceramic tile. A wet saw equipped with a good diamond blade is a necessary tool. Many tile setters use kneepads, but when setting stone, it is important that your knee pads do not scratch the surface of the stone. It may be a good idea to tape Styrofoam to the kneepads. Check them often as you work to avoid picking up sand and stray grit.



Setting Materials:

Many of the setting materials that are used for ceramic tile can also be used for stone tile, but there are some exceptions. Many green marbles cannot be set in water-based setting materials. If they are, they can curl at the corners. I have received calls from dozens of installers who made this mistake. Green marble should be set in epoxy and not in water-based materials such as thinset or mud. However, I have been told that there are several water-based materials that are being developed specifically for these difficult materials. Check with the manufacturer and make sure their material is recommended for setting green marble.

Another problem with certain setting materials is what is called "Bleed Through." Many translucent stone tile (whites and lighter colors) will permanently darken if a gray setting material is used. It is always a good idea to use a white setting material when setting stone to avoid this problem.



Setting:

The procedures for setting stone or ceramic are relatively the same, but again we have some differences that should be noted. Due to the smooth backing of stone tile, it is of utmost importance that stone tile obtain 100 percent contact with the setting material. These procedures are detailed in The National Tile Contractors Association Reference Manual and the Marble Institute of America Design Manual.

Before any stone tile is set, it is a good idea to lay out the tile dry. Since stone tile varies from tile to tile, you will need to lay out the material to make sure you do not set tiles that would not be aesthetically pleasing. This of course involves a lot of extra time, but you do not want to hear some of the stories where customers refused to pay for an installation because the veins were going in the wrong direction or there were shading differences from one tile to another. Perform a dry layout, get the customer's approval, and you will avoid any problems.

Avoid using excessive amounts of water when installing stone tile. Too much water can cause a condition known as efflorescence. Efflorescence can be detected by a white powdery residue developing on the surface of the stone. This powdery residue is dissolved salts from the setting bed being carried to the surface. If this condition occurs, the salts can be removed by dry buffing the tile with a soft cloth. The efflorescence will stop when the setting bed completely dries.



Grouting:

Stone tile should always be set with as narrow a grout joint as possible. You will need to avoid grout joints over 1/8 inch. The reason is simple. If stone tile, especially marble, is set with a wide grout joint, you will need to use sanded grout. Sanded grout will scratch stone tile. The only way to remove scratches from stone tile is to hone and polish the surface. If sanded grout is used, the honing process will pull the grout out, and it will re-scratch the tile. The grout will have to be removed prior to any honing. This can be costly and very time consuming. Always set stone tile with narrow grout joints and only use unsanded grout.

Another grout type that is becoming popular is epoxy grouts. Epoxy grout on certain types of stone can cause problems. Some of the darker epoxy grout can bleed into the stone causing permanent staining. This is especially true on granite. Granite tends to be more porous than marble, and can absorb epoxy very readily. If using epoxy grout on stone, it may be a good idea to do a mock-up installation. Also check with the grout manufacturers; there are available several non-staining epoxy grouts.



Clean-up:

You just completed a beautiful stone tile installation. You were careful in preparation, you used the proper setting material, and you used unsanded grout. You're ready for clean-up. You end up using the grout cleaner you have always used, and what happened? The shine on the stone is gone. This is a common mistake that is made by many. Most grout cleaners are acid- based, and acids will affect marble tile. Never, never, never use acid-based cleaners on marble tile. Use only neutral cleaners and water. Non-acid grout cleaners are now available from several stone maintenance supply distributors.



Care and Maintenance:

It has been my experience that many tile setters do not care what happens to the tile installation once they have been paid. Do not make this mistake. Always give your customers the proper care instructions. On marble tile, NEVER recommend or use vinegar and water. Vinegar contains acetic acid that can dull the marble. Recommend only a good neutral cleaner or stone soap. The Marble Institute of America has designed a care guide for marble and stone. Give this to your customer and read it yourself. More installations have been damaged due to improper care and maintenance than by any other procedure.

These are just a few of the differences between setting ceramic and stone tile. Most of the problems can be avoided by a thorough understanding of the materials used. There are available several sources for proper installation methods. The Marble Institute of America can be reached at 614-228-6194 or www.marble-institute.com. The National Tile Contractors Association 601-939-2071 or www.tile-assn.com/. The Tile Council of America 864-646-8453 or www.tileusa.co