July 27, 2007
The glass tile segment of the tile industry seems to be continuing its stellar growth. I have been around awhile, and am always continually amazed at the creativity of those in the tile industry. This is readily apparent in the current offerings from the glass segment of the tile industry. At the recent Coverings show in Chicago I marveled at the amount of different glass products offered. As beautiful as they are, for the installer glass adds a new complexity to the installation process.
There are multiple processes of manufacture offering a multitude of patterns and sizes. Type of glass, backing, and size all require much more consideration than your typical ceramic tile. A fair learning curve still exists with glass tile products, especially in the larger sizes. Given the lack of consensus on installation of large glass, we will focus on the known cautions for all glass either large or small. This is an article about how to avoids callbacks and keep your money when installing glass.
Installation is the key to keeping beautiful things beautiful, customers happy, and protecting profits. While installers are grappling with methods of installing increasingly large porcelain tile, many lessons have been learned about installing impervious products. This is a good thing, as glass is also impervious, but glass tile brings with it a different set of needs for successful installations above and beyond those used for porcelain. In the case of glass, “tile is tile” does not apply. There are many concerns and considerations that need to go into successful installations of glass tile that may be “overlooked” without causing failure with other tile products.
Glass tile has been installed successfully using mortar beds for hundreds of years and mortar is still the preferred method of installation by trained industry professionals. However, today’s building methods and practices often don’t allow the opportunity for conventional (mud or mortar) installations. Additionally, the qualified labor available for this type of work has always been in short supply. Today we are in a thinset or thin-bed world where we bond directly to substrates. Glass tile can be successfully installed using these today’s methods by experienced tile setters.
With glass tile becoming a commonplace, there are now American National Standards (ANSI) for their installation. The recent completely revised ANSI A108 (American National Standards for the Installation of Ceramic Tile) will contain three new methods representing a balanced consensus of industry organizations. The new standards are for glass mosaics, tile smaller than 3”-by-3”. Given the wide range of properties on larger sized glass they were excluded from the new standard but the basic principles remain the same. The new standards are: Installation of Paper Faced Glass Mosaic Tile A108.14-2005; Alternate Method: Installation of Paper Faced Glass Mosaic Tile A108.15-2005; Installation of Paper Faced, Back Mounted, Edge Mounted, or Clear Film-Face; Mounted Glass Mosaic Tile A108.16-2005.
These standards contain detailed guidelines for successful installations established by many years of field experience and intensive testing in the field and independent laboratories. As with any ANSI method, manufacturers written instructions and local codes always prevail. Certain types of products, geographical areas, or construction practices may dictate additional considerations not addressed in the standards recommendation. The intended use of any standard is a minimum guideline for successful installations. Let us move on to some considerations with all tile products but particularly critical to glass tile.
Starting with the sales process, the end user needs to be aware that movement accommodation is critical with glass products. The aesthetically displeasing appearance of sealant cannot be overlooked in glass installations as it often is in other types of installations. Lack of movement accommodation is present in an overwhelming amount of tile installation failures and numerous glass tile installations. Movement (expansion) joints are a very tough sell to an end user.
Throughout my career it was always a battle to tell someone you needed to put a caulk joint in the middle of their 40-foot room or at the perimeter of their room. If you answered the phone calls and emails received about failures, their importance would be much clearer. Glass tile has a high degree of expansion and contraction. Movement or “expansion” joints are a requirement of every successful tile installation. There is no place this is more true than glass tile. Maximum spacing of joints needs to be every 20 to 25 feet interior and 8 to 12 feet in exterior or in areas exposed to sun or moisture. A 1/8-inch gap should be left at all wall joints. There are many additional recommendations contained in the Tile Council of America Handbook under EJ 171. These joints can be very disturbing to the end user if they are not aware of the necessity. On more than a few occasions I have been accused of trying to destroy the ambiance sought after and paid for before I got on the job. There are many areas an installer can deal with; destroying the dream sold to the customer is not one of them. The awareness of this vital component of installation needs to start with the sales process.
Glass tile manufacturers typically have very specific setting material recommendations. It is doubtful that mastic would adequately dry and is never recommended. Epoxy material seems a natural selection but it is too brittle to allow the movement needed by the expansive nature of glass tile. Modified thinsets are needed whenever a material is set in the thin-bed or direct bond method. While thinset is fairly universal with ceramic tile, that is not true of glass products. Size also makes a difference when selecting thinset; some have size limitations. Close attention should be paid to the recommendations of the glass tile manufacturer. Most have done extensive testing and base their recommendations on that testing and field experience. History has shown it is not wise to second-guess manufacturer research and field experience in the unlikely event there are any claims. White thinsets are preferred by most to minimize and avoid any shading. When liquid latex is offered, all other things being equal, it will offer superior performance by its better adhesion and drying properties.
Glass tile is a top shelf product requiring top shelf setting materials for proper bonding. If the tile will be exposed to moisture make sure the setting material is rated for such applications. Some thinsets will re-emulsify in wet applications. Spreading the thinset also varies from traditional tile. Back buttering is always a good idea on any tile; it should be considered mandatory with all glass tile other than mosaics, those less than 6 square inches. Glass tile is also not typically set into combed thinset. The spreading application for glass is key in the surface; comb the thinset with the notched side, and then make another pass with the flat side to flatten the ridges. The back buttered tile should then be placed into the fresh thinset mortar and beat in with a beating block to assure coverage and flatness. Notch size recommendations vary with the size of tile. Make sure the tile is dry and clean when thinset is applied. It is wise to wipe the back of the tile with a clean dry towel. A problem frequently seen in cracked glass tile complaints is excessive thinset applied under the tile. Tile setters often do this for “out of square” conditions or where a surface is not flat and level; we call it “padding the tile”. All thinset shrinks as it dries some more than others. This shrinkage may result in cracked tile. The area where the tile is to be installed needs to be properly prepared before installation. The tile setter will not be able to correct out of square or plumb (flat) conditions with thinset without potentially having a detrimental effect on the tile when it is installed.
When it comes to cutting glass tile, as you may have come to expect, things are also a little different. Some glass tile can be easily scored and snapped with a quality cutter like most ceramic tile. Some require scoring both sides of the tile and still others can only be cut with a wet saw. Special glass blades are available though in most instances a quality porcelain blade will suffice. Quality is a keyword here. Glass tile likes fine diamond grit and lots of it. It also likes lots of water and very little pressure when being cut. There are quality score and snap cutters available that will work on some glass tile products as well as glass specific hand tools. When installing tile with a backing, some manufacturers recommend cutting from the backside of the tile.
Gout as we have come to expect, also varies by product. Recommendations are typically based on joint with and the properties of the tile. Some scratches easily, while most do not. Check for recommendations on either sanded or unsanded. Another serious consideration is drying time. Joints are better left ungrouted until the thinset has reached an initial cure. This can vary widely with type of thinset and the environmental conditions of the installation. The bond to glass is very fragile during the initial drying stage and should not be disturbed until it has achieved adequate strength. With smaller tile, such as 1-by-1 or 2-by-2, a few days may be all that is necessary. However, as the tile gets larger, the drying time increases. Even with ideal environmental conditions, you should think in terms of days, not hours for larger glass tile. Additional time should be added for low temperatures or high humidity. Sealing glass tile serves no purpose. Grout can always benefit from a sealer but once again, drying time can be extended before the application of grout sealers.
With such a wide range of materials available you need to know your specific product manufacturers recommendations so you can properly prepare your customer and installer for accommodations they may not have customarily made for other types of ceramic tile installations. Glass tile has very specific needs for successful installations. I do not think glass tile is much more difficult to work with than other tile products. But, it does not offer the “forgiveness” of other tile products. It requires both experience and strict adherence to well established installation procedures for successful. Good installations make for happy customers and that is what we all want.