Glass, Glass, and More Glass
June 1, 2006
Just when we were getting used to porcelain tile products, along comes an old product with a new focus.
Growth in the glass tile segment of the tile industry is nothing short of stellar. I have been around awhile, and am always continually amazed at the creativity in the tile industry. I struggle to think of any product market, cars, furniture, or even toys, that is blessed with the creative talent and dedication as good as those who work in the design part of the tile industry. This is readily apparent in the current glass tile offerings. But, as many of you know, my dedication is on the installation side of the tile equation so this is not an article about how to sell glass. Rather, it is an article about how to keep your money when you're installing glass tile.
Installation is the key to keeping beautiful things beautiful, customers happy, and protecting profits. Many installers are still grappling with the issues of installing large porcelain tile. Now with the increasing popularity of glass tile, many are applying some of the lessons learned about installing impervious products such as porcelain and glass. This is a good thing in many respects but glass tile brings with it a different set of needs for successful installations above and beyond those used for other ceramic products. 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 in other product segments of the tile industry.
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 and the qualified labor available for this type of work has always been in short supply. Today we are in a thinset or thinbed world where we bond directly to substrates. Glass tile can be successfully installed using these methods by experienced tile setters over cementious or dimensionally stable surfaces.
Glass tile installation has become a commonplace to the point where for the first time we will have American National Standards (ANSI) for its installation. In the third quarter of 2006 a 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 for glass will be:
These standards contain detailed guidelines for successful installations established by many years of field experience and intensive testing by 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. Its intended use is a minimum guideline for successful installations.
Let us move on to some considerations with all tile products but particularly critical to glass tile. Before a single tile is set, and starting with the sales process, is movement accommodation. Lack of movement accommodation is present in an overwhelming amount of tile installation failures. This is 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 and at the perimeter of the room. Glass tile has a high degree of expansion and contraction; movement or expansion joints are a requirement of every tile successful installation. There is no place this is more true than glass tile. Maximum spacing of joints needs to be every 20 to 25 feet for interior applications and 8 to 12 feet in exterior applications 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 method 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 "look" sought after and paid for before I got on the job. Please educate yourself and the sales people in this critical performance area. There are many areas an installer can deal with on the job; destroying the dream sold to the customer by the salesperson is not one of them. The caulk or sealant needed for these joints should be made part of the sale and matched to the grout as closely as possible. This requires advanced ordering and consideration during the grout selection process. Another possibility is a premade movement joint offered by many manufacturers. You can often turn these into design statement making it a desirable part of the installation. We did it for years; it works.
Glass tile manufacturers typically have very specific setting material recommendations. Mastic will never adequately dry whether used on the floor or wall. 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 thinbed or direct bond method. All glass is not equal! Each possesses different properties from different processes of the manufacturer; 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. It is not wise to second guess their research and field experience in the unlikely event (with proper installation) there are any claims. White thinsets are preferred by most to minimize and avoid any shading. When a liquid latex is offered, all other things being equal, it will offer superior performance by its better adhesion and typically fast 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 over 8-by-8; it is mandatory with 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 to 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 glass tile with a clean dry towel. One other problematic area with glass 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." As thinset shrinks some as it dries, this is not a good idea and can 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. The 12-by-12 glass tile shown in pictures accompanying this article was sent to us because the installer claimed it could not be cut without excessive breakage. The saw shown along with several others had no problem cutting a ?-inch off chip free. We also drilled a hole in the other sample of the same tile; as you can see, there were no problems there either. Specialized equipment is not always required. One manufacturer recommends using a glass cutter and thick piece of wire for straight cuts. It doesn't get much simpler.
Grout, as we have come to expect, also varies by product. Recommendations are based on joint with and the properties of the tile. Some glass tile scratches easily; most does not. Check for recommendations on either sanded or unsanded. This will also determine joint width as unsanded can not be used in a grout joint wider than 1/8-inch. 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 environmental conditions. 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. Given ideal environmental conditions, you should think in terms of days, not hours for larger tile. Additional time is required 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.
The preceding article can only be considered a general overview of considerations for the installation of glass tile. There are always going to be exceptions to the rule. Most importantly, you need to know your products and their recommendations so you can properly prepare your customer and installer for accommodations they may not have previously made for other types ceramic tile installations. Glass tile has very specific needs for successful installations. Good installations make for happy customers and profitable trouble-free installations, and that is what we all want.