Loose tiles
Perhaps the most striking thing about visiting a tile store is the vast array of tile available. Produced in a wide spectrum of colors, sizes and shapes, tile is sold mainly as separate, loose tiles, all of which share a common requirement in setting: They must be consistently spaced. Setters installing loose tiles have used any number of devices to space them evenly—sticks, nails, string or rope, and, since their development in the late 1950s, tile spacers. The latter are small plastic devices sold in various shapes and widths that establish consistent grout joints between tiles. Some manufacturers resolve the problem of spacing by building spacing lugs into the sides of the tile or by packaging tile in sheet format.
Sheet-mounted tiles
Sheet-mounted tiles are individual tiles evenly spaced and mounted on a backing sheet, approximately 12 in. square or larger. Various kinds of tiles are packaged in sheet format, but most are vitreous, no larger than 4 in. square and mounted on paper, plastic mesh or a grid of rubber dots (see the photo below). The placement of the mounting material distinguishes the several types of sheet-mounted tile. As its name suggests, face-mounted tile has its mounting, a sheet of paper, adhered to the face of the tile. This paper is left in place during setting and is dampened and removed after the adhesive has dried. Back-mounted tile is held together by plastic or paper mesh applied to the back of the tile, which is left in place when the tile is set. Dot-mounted tile is joined by small rubber or plastic dots between the joints, which are not removed for setting. Wherever the mounting is positioned, the sheet of tiles can be easily trimmed to approximate size with a sharp utility knife, a razor knife or an x-acto blade.
The obvious advantage of placing the mounting material on the back of the tile is that the face is then visible during setting, making it easier to align the tile and grout joints. The disadvantage of this arrangement is that the backing material interferes with the bond of the tile and adhesive. In the case of dot-mounted tile, some setters also report installation problems caused by a thin film of oil deposited on the back of the tile when the dots were applied.
Tile backs
Although a tile’s face gets most of the attention, its back deserves note, too, since it’s often intentionally covered with raised ridges, dots or squares. The configuration of a tile back varies greatly from tile to tile. It is consistently designed either to expand the surface area of the back (or thus increase the adhesive’s bond strength) and aid in the firing process or denote manufacturing information.
Ridge-backed tile is extruded tile whose back bears a series of elevations, which can effectively double, and in some cases even triple, the flat surface area of the back. Button-backed tile has raised dots or squares on the back, which separate the individual tiles when they’re stacked in a kiln, allowing heat to pass evenly among them and ensuring a uniform firing. Finally, many tiles are embossed with identifying marks to denote a particular production run of tile or to record color and other manufacturing specifications. All of these various markings can be helpful when you need to find replacement tiles for restoration or remodeling work.
Glazed wall tile
Generally speaking, glazed wall tile is nonvitreous tile with white gypsum or terra-cotta-colored bisque and a soft glaze, which makes it unsuitable for floor use. In contrast, floor tile is any nonvitreous, semi-vitreous, vitreous or impervious tile, whether glazed or unglazed, that is considered sturdy enough to be used for floors. This tile could, of course, also be used for walls, as perhaps some of it should be—some tiles officially classified as floor tiles are not particularly durable, or they may have a tough vitreous bisque finished with a fragile glaze.
Most glazed wall tile sold in the United States is produced in this country by the dust-press method. Usually about 1/4 in. thick, these tiles are most commonly made in 4 ½ in. and 6-in. squares, though larger tiles up to 12 in. square are available. With a few exceptions, these tiles are intended for wall use, rather than for floor and countertop installations. With proper waterproofing, they can be used for wet installations, but they should be limited to interior use, as they are not freeze/thaw stable. Glazed wall tile requires no special setting bed and can be installed with either an organic mastic or a thinset adhesive for dry installations, but should be used only with a polymer-modified thinset adhesive for wet installations.
