Art & Decorative Tile Techniques: Stone Tile Fabrication Techniques
Stone tiles were in popular use long before ceramic tiles were perfected, but after thousands of years, installers today rarely take the time to provide the detailing that has always stood for craftsmanship. Stone can be cut into blocks, slabs, tiles, and trim shapes that are available from most well-stocked stone suppliers, who also may cut slabs to size and shop-polish the edges for fabrication on-site. The installation of slabs requires specialized tools and skills that take years to hone, but the installation of stone tiles is relatively simple with the tools you already use for installing ceramic tiles. Practically anybody can install stone tiles, but to make the installation professional looking requires the ability to profile and polish an edge, and that requires several additions to your tool kit. But before we begin fabricating, let's cover some of the basics about stone tiles.
Surface PreparationThe setting bed should be flat and level to within 1/8-inch in 10-feet for tiles up to 12-inches, and within 1/8-inch in 10-feet for larger tiles. The allowable deflection of the floor, or the space between joists, should be no greater than what is allowed by the stone distributor or manufacturer: For ceramic tile and a few stone tiles, the industry standard limits deflection to 1/360th of the span of the unsupported floor or the distance between joists. For many stone tiles, though, deflection must be reduced to L/480, L/720 or more, depending on the stone. The setting bed must be dust-free and clean, and all the setting materials should be acclimated to room temperatures for at least 24 hours.
Surface preparation is a normal part of the tile installation process. In fact, surface preparation continues even after the stone tiles have been installed: Surface preparation includes maintaining fresh tiles in an optimal condition while the adhesive-the thinset mortar-cures before installing the grout. It also includes maintaining the grout until it fully cures, and the application and curing of any sealant or sealers that are included in the installation.
SortingWith few exceptions, all the stone tiles you receive for installation will be different from each other in color, hue, surface features, texture and other characteristics that may sometimes contrast or even clash. For this reason, all the tiles should be laid out, observed, and sorted to best complement the installation and avoid glaring contrasts between neighboring tiles. This takes time, which should be figured into your bid or estimate, but is another detail found that separates the ordinary from professional installations. Tiles with obvious, hollow-sounding veins should be culled or used for cuts, and tiles that are excessively thick or thin are set aside and often used on closet floors, or other infrequently seen areas. Check also for manufacturing "milk," the thin, dusty residue sometimes seen coating the backs-and some times the front-of stone tiles. This dust layer, leftover from the manufacturing process, is a bond breaking substance that must be cleaned off with all tiles rinsed with clear water before installation. If you cannot sort the tiles into a useful pattern or insert, at the very least, shuffle the tiles, as they are removed from their containers, to help evenly distribute any anomalies.
LayoutThe layout of stone tiles should be done according to the same ANSI A108 specs used to install ceramic tiles; that is, no tiles less than half size where possible, balanced cuts on either side of the floor, with the best layout preserved for the focus floor. A good layout is a part of the artistic side of tile installation, whether ceramic or stone, and an opportunity for the installer to make craftsmanship noticeable and appreciated by anyone with an eye towards beauty.
InstallationThe interface between stone tiles and the setting bed is critical since the properties-and strength-of every stone tile varies within each tile: Do not expect that any stone tile has the reliable strength of ceramic, and can bridge over gaps in the adhesive. Stone tiles should always be installed with the ANSI A108 minimum for wet areas: 95 percent uniformly distributed adhesive contact. This can be improved a few percentage points by back-buttering each tile with a uniformly thick 3/32 coating of latex thinset, and using the industry-approved "hinge-and-slide" method when bedding each tile. Don't expect to achieve optimal adhesive contact without creating something of a mess, so clean off the surface and around the edges of all tiles before moving on to the next area: 2/3 of the thickness of the tile should be open and free to receive grout.
DetailingSince cutting is an important part of each installation, you should have a good-running wet saw equipped with a blade appropriate for the material you need to cut. There are soft, all-purpose, and hard blades available to any installer who sets stone tiles frequently.
If you already use a wet saw for cutting ceramic tile, you already know the drill for cutting on a wet saw: always keep plenty of fresh water on the blade for cooling, ease the tile into the blade and start slowly, pick up the feed rate through the body of the tile, then slow down so the blade can exit the tile without damaging it.
By replacing the blade, the same saw you use to cut tile can also be used to produce bullnose and other trim profiles. For these 3/8-inch thick tiles (1/2-inch or thicker tiles, as well), the process begins with cutting all the trim tile stock to size. For this article, cutting base trim that is 3 1/2-inches wide allows me to get three lineal feet of trim from each piece of 12-inch tile. Next, I use a diamond blade to rough the corner of each piece, and then feed them into the profile blade in three or four steps. I could cut the profile in one step, but the wear on the blade would be excessive and unacceptable. Instead, after roughing each tile with the angle grinder, I adjust the fence so that only a small portion of waste is removed at each pass, and send all pieces of stock through the saw at each setting, to speed the process, until the desired profile is achieved. The next step is to remove the scratches left by the wheel and polish the exposed edge.
PolishingEdge polishing is one of the hallmarks of a professional installation. On some stones, it can be done using wet sand paper available from the local hardware store, but for the best possible finish, and a polish to match the manufacturer's, I utilize a kit made from two sets of pads-one for on-site dry polishing, and another for wet polishing at the shop.
Edge polishing is a two-part process composed of several steps. The first step is to remove all scratches made by the profiling wheel, while the polishing process involves using increasingly finer grits to produce a variety of surface finishes from honed to high-gloss. To begin the process using wet-cutting tools, I use a XX-grit pad mounted in an MK XXX wet grinder made specifically for safe wet polishing. First, I ensure that plenty of cooling water is flowing through the spindle, and then I begin an up-and-down motion with the grinder, to cover all the rough material exposed by the profiling wheel. Again, to save time, I run all the pieces through each grit stage until the desired finish is obtained, and use plenty of water to flush rougher waste grains away before switching to a finer grit. Hook and loop pads are the industry standard for changing discs, with quick-connect options available from a limited number of manufacturers.
If possible, try to determine what grit the manufacturer used to polish the field tiles, and use that grit to finish the edge of your baseboard tiles. Use an air blast to dry the treated area, and be careful to observe the texture before and after each stage polish-this and patience are the hallmarks of a professional job well done.
Compared to an installation whose exposed edges are sharp and marked with repeat ridges made by the saw blade, a craftsman's installation is beautifully detailed regardless of the style or décor, and adds significant value to any structure. For the installer, it is an opportunity to turn the ordinary into a real work of art.