Tiles from Stone
Natural stone tiles can be beautiful but as a natural product they are less uniform in color and pattern, and require more planning for use and installation. Mass-produced stone tiles are uniform in width and length. Granite or marble tiles are sawn on both sides and then polished or finished on the top surface so that they have a uniform thickness. Other natural stone tiles such as slate are typically "riven" (split) on the top surface so that the thickness of the tile varies slightly from one spot on the tile to another and from one tile to another. Variations in tile thickness can be handled by adjusting the amount of mortar under each part of the tile, by using wide grout lines that "ramp" between different thicknesses, or by using a cold chisel to knock off high spots. Some stone tiles such as polished granite, marble, and travertine are very slippery when wet. Stone tiles with a riven (split) surface such as slate or with a sawn and then sandblasted or honed surface will be more slip-resistant. Ceramic tiles for use in wet areas can be made more slip-resistant either by using very small tiles so that the grout lines acts as grooves or by imprinting a contour pattern onto the face of the tile. The hardness of natural stone tiles varies such that some of the softer stone (e.g. limestone) tiles are not suitable for very heavy-traffic floor areas. On the other hand, ceramic tiles typically have a glazed upper surface and when that becomes scratched or pitted the floor looks worn, whereas the same amount of wear on natural stone tiles will not show, or will be less noticeable. Natural stone tiles can be stained by spilled liquids; they must be sealed and periodically resealed with a sealant in contrast to ceramic tiles which only need their grout lines sealed. However, because of the complex, nonrepeating patterns in natural stone, small amounts of dirt on many natural stone floor tiles do not show. The tendency of floor tiles to stain depends not only on a sealant being applied, and periodically reapplied, but also on their porosity or how porous the stone is. Slate is an example of a less porous stone while limestone is an example of a more porous stone. Different granites and marbles have different porosities with the less porous ones being more valued and more expensive. Most vendors of stone tiles emphasize that there will be variation in color and pattern from one batch of tiles to another of the same description and variation within the same batch. Stone floor tiles tend to be heavier than ceramic tiles and somewhat more prone to breakage during shipment.