Stone Tile Selection
Until about 50 years ago, most stone tiles came from quarries that had operated for hundreds or even thousands of years. These quarries were discovered and developed long before national or international standards, precision measuring equipment, or reliable test labs. Properties of stone were determined the hard way through trial, error, and experience. Over time, a history of use revealed any shortcomings of a particular stone, and as quarries supplying unusable materials were abandoned, quarries supplying good stone gradually accumulated catalogs of successful projects that were used to help sell the strength of their products. With this approach, precise measurement of properties was far less important than a stone’s ability to perform in a variety of environments such as: dry tropical (high heat), wet tropical (high heat and humidity and frequent rainfall), light-, moderate-, or hard-freezing (freeze/thaw cycles), continually submerged in water, and so on. As you might imagine, most of the history of the use of stone tiles involves big-budget projects for significant state or religious buildings.
That installation, using suspect tiles, only persists because the half-bath is very low use, and has never been subject to harsh cleaning methods. For an active household, though, those somewhat fragile tiles would be a mistake. How is an installer to know what to use and what to avoid? The first step is to understand that the fundamental difference between ceramic and stone tiles is that the properties of ceramic tiles are fixed by a combination of: ingredients for producing the tile body and tile glazes, how the ingredients are converted into a tile shape, how long the raw tiles are fired in a kiln, and how hot the kiln is fired. By altering the recipe, ceramic tiles exhibiting a wide variety of properties can be produced accurately and consistently. On the other hand, the properties exhibited by most stone tiles is expected to vary within the blocks quarried for stone, within any given batch of the same stone tiles, and within an individual tile.
As well, in spite of positive test results, unknown and unforeseen properties of stone may affect performance and durability. For this reason, while tests may confirm that a certain stone tile is suitable for an intended use, I prefer to use a selection method that avoids any shortcomings with testing. The method is relatively simple, but I use it to quickly determine suitability. Simply put, I ask the supplier to provide the location of a similar installation using the same tile I am considering. Claims of suitability often vanish once that question is asked, and whether the project is multi-million commercial or a simple household floor, it is always the first question I ask.
Many installers learn the hard way about stone tile installation, and often give up on stone after their first major problem, but to the installer who wants a challenging creative outlet, and a more profitable business, stone tiles present many opportunities. If you have an interest in installing stone tiles, I recommend membership in the Marble Institute of America (MIA) as an informative first step. MIA is a gateway to materials, methods, and techniques, and their Dimensional Stone Design Manual should be in every serious installer’s technical library. Armed with this knowledge, a profile wheel and a set of grinding and polishing pads, many installers have seen their interest grow into a full-time business.
Selecting the right stone tile is only the first step. Most stone tile floors require a stiffer structure than what is acceptable for ceramic tiles: make certain that the structure you want to tile meets the tile supplier’s requirements for deflection. Be especially careful of any structure that requires a crack isolation membrane system for the safe installation of the stone tiles selected for your project. Finally, since there are a number of bonding issues with stone tiles, don’t try to economize by selecting sub-par installation materials.
Author’s Note: In the interest of full disclosure, lest some readers think I am biased against stone or stone tiles, my wife and I absolutely love our wildly colorful Blue Louise granite kitchen, and with the exception of my wife’s tiles, or book projects using ceramic or porcelain, I have only worked with stone tiles since moving back to the west coast about 10 years ago. My 1995 Vermont HBA Best Bathroom Award featured several varieties of stone tiles.
- Marble Institute of America (MIA), www.marble-institute.com
- Tile Council of North America (TCNA), www.tileusa.com
- All photos courtesy Mike Mesikep