Glass tiles are a popular alternative to ceramic or stone tiles, and use the same basic installation methods. There are several different types of glass tile available. Glass mosaic tiles, the most familiar, are 1” or 2” tiles face-mounted on sheets, uncoated glass tiles larger than 2” x 2” and coated glass tiles larger than 2” x 2”. Glass tiles share some similarities with ceramic tiles: The thin decorative surface of glazed wall tiles is glass, and the entire body of porcelain ceramic tiles is vitrified like glass. Nevertheless, glass tiles require careful detailing for a successful, long-lasting installation.
Before installation begins, you should familiarize yourself with the glass installation methods found in the Tile Council of North America’s (TCNA) tile installation handbook. It is highly recommended that designers, specifiers and tile installers also familiarize themselves with the ANSI A108.1 handbook and its specifications related to glass tiles. Both booklets are available through TCNA at www.tileusa.com.
Of the three major types of glass tiles, those larger than 2” x 2” and those with coated backs may be difficult to bond properly to either dry or wet-area substrates – even though glass, by itself, is an ideal material for use in wet areas. Back-coatings may be nothing more than regular paint, but coatings may also be made from durable, water-resistant materials. Some are made of colored glass fused to the backs of the tiles, and the backs of some glass tiles may be coated with reflective films. Regardless of the composition of the coating, following the glass tile manufacturer’s adhesive recommendations is essential to eliminate any compatibility issues.
Though glass installation methods are found in the TCNA Handbook, if the manufacturer’s instructions call for a specific method or backing, those instructions should be followed. If there is a problem with the installation and you use a different adhesive, you have bought the failure.
The same recommendations apply to non-coated and mosaic glass tiles. Plain glass tiles may not have any compatibility issues, but coated or not, glass tiles may be difficult to bond properly. Additionally, since uncoated glass tiles are transparent, how an adhesive is applied is an important consideration for two reasons: Notch trowel marks can be seen through the tiles, and if water or moisture seeps into the resulting adhesive voids, mold can grow and give the glass tiles an unsightly appearance that is impossible to remove.
As with any tile – ceramic, stone, or glass – using the right size notch is one of the most important parts of a tile installation for either a dry or wet area. Eliminating any voids behind a tile helps prevent cracking and the appearance of mold, and on exterior installations minimizes freeze/thaw problems. The best way to do this is to maintain the industry-recommended minimum 95% adhesive coverage (the industry minimum for tiles installed in dry areas is less, but installers will do well to stick with the 95% minimum). While 95% is good, when you can see right through the body of glass tiles, even the slightest voids will be visible.
Regardless of the tile I am installing, instead of reading the suggested trowel notch chart on a sack of thinset, I prefer to test trowels out on the installation substrate, using the tiles that are to be installed, and select the trowel that yields at least 95% coverage. On all installations – regardless of the type of tile – I back-butter each tile in addition to the thinset mortar I spread over the substrate. I do this to achieve the maximum possible adhesion, but with glass tiles, back-buttering also helps mask any voids in the adhesive bed that might show through the tile.
The type and color of the adhesive are also important. Use whatever the glass tile manufacturer requires, but if nothing is specified, a high-strength latex or epoxy thinset should be used. As for color, to help produce a bright appearance, use white thinset because grey tends to dull down the color.
Aside from ensuring that no voids are visible, the installation of glass tiles larger than 2” x 2” is otherwise the same as installing any other type of tile. For installing mosaic glass tiles (2” x 2” or smaller), there are two installation methods. The first method has been used for centuries and is more suited for skilled installers who can float mortar because the face-mounted sheets of glass are installed while the mortar is still soft. As well, grout is applied to the back side of the tiles before the mosaic sheet is positioned over the wall. This method is not for the faint of heart; it requires skill and practice, and is not recommended for novice or part-time installers.
The other method is considerably easier and requires far less skill. The mosaic sheets are installed over a hard substrate, and the grout is installed after the tiles have set up. The first step is to spread the adhesive, and because mosaic tiles are so thin, I use the smooth side of the trowel to flatten the ridges made by the notch trowel (Photo 1). This step will prevent adhesive ridges from oozing up and clogging the grout joints.
Next, the mosaic sheets are installed (Photo 2) and positioned so that the joints between sheets are uniform and match the grout joint width (Photo 3). Once positioned, the sheets are flattened with a beating block and hammer (Photo 4). This step not only smoothes the surface of the sheets, but ensures that each tile is fully bedded in the adhesive. At this point, the adhesive is allowed to harden and cure.
Once the sheets are locked in the cured adhesive, the paper facing is soaked with water (Photo 5). After a few minutes – once the glue holding the paper has softened – the paper can be removed (Photo 6). In hot weather, the paper must be kept soaked: if the paper dries out, the glue holding it to the face of the tiles will not soften and dissolve and only a portion of the paper will come off. Once the paper has been removed, any residual glue must be removed with a sponge before the grout is installed (Photo 7).
If you follow all of these steps, you will create a beautiful, durable installation. It can only elevate your career to learn how to install glass tile correctly.