Glass Tile on Floors! Are You Kidding?
While the majority of glass tile manufacturers focus their efforts on decorative tiles, suited for walls only, there are a growing number of glass tiles suitable for residential and light commercial floor applications. Glass tile is now available in numerous sizes, shapes, colors, finishes, slip ratings and body strengths, all of which should be considered prior to specifying glass tile as flooring. Test results using the American Standard Test Method (ASTM) C 648 Breaking Strength test, which determines the amount of force it takes to break a tile (tile body strength) and ASTM C1028 test, which determines static coefficient of friction (slip resistance) provides insight into how a glass tile may perform in various environments.
An example of breaking strength, set by the American National Standards Institute (ANSI), is the minimum of 250 pounds of force for unglazed pavers. Glass floor tile with breaking strengths of over 800 pounds of force are now available. These high breaking strengths demonstrate that glass tile can be manufactured to the same performance standards as tile traditionally used in light commercial flooring.
This is a surprising revelation to many. However, body strength alone does not make a glass tile great for floors! To slip or not to slip - this is another important question when specifying any type of flooring.
To determine how slip resistant a tile might be, dry or wet, we can enlist ASTM C1028 the current American standard for determining the static coefficient of friction of for tile surfaces. This is an important consideration in selecting the appropriate glass tile for flooring applications in public spaces such as lobbies or restaurants. Always consult local code in order to ensure compliance with OSHA and Americans with Disabilities Act (ADA) recommendations. Another vital aspect of the specification process is the installation procedure. In further evaluating the viability of glass, we turn our sights to preparing the bonding surface (substrate).
Substrate preparation, the most critical part of any tile job, is similar to most other tile with the exception of seven day minimum cure times for all mortar beds and the exclusion of any wood substrates.
TCA F102-03: Recommended for exterior floors, decks or patios (concrete cured 28 days minimum) where positive drainage below slab is provided, with a maximum variation of 1/4-inch in 10 feet from the required plane.
TCA F111-03: Recommended for use over structural floors subject to bending and deflection with a maximum variation of 1/4-inch in 10 feet from the required plane.
TCA F112-03: Recommended for use over mortar beds cured a minimum of 7 days, in slab on grade construction where no bending stresses occur.
TCA F113-03: Recommended for mortar beds cured a minimum of 7 days.
Room to Move
Expansion provisions are another part of the installation that should never be overlooked in glass tile projects. Since the needs of each installation vary an architect should specify the location, depth, width and type of expansion material as recommended in TCA EJ 171-03. In the event your project lacks specifications, and you are confronted with making on site decisions, please do not cover existing expansion or control joints in the slab. General recommendations are to place movement provisions every one hundred square feet, at floor perimeters to reduce contact with walls, and around column bases, fixtures, piers and retaining walls. Frequency, depth and width also increase with extreme variations in temperature such as direct sunlight. Sheet and trowel-able membranes do not eliminate the need for expansion provisions and although the recommended adhesives are usually very flexible they are designed to work with expansion provisions not to replace them.
Adhesives recommended by glass tile manufacturers vary from pure silicone to highly flexible118.4 latex Portland cement mortars. The majority of glass tile makers recommend specific 118.4 mortars as the result of collaborative testing, between glass tile and adhesive manufacturers. If the glass tile you are installing lacks a specific adhesive recommendation please contact 118.4 mortar manufacturers for a list of their products approved for setting glass tile. Not all 118.4 adhesives are recommended for glass tile so consult manufacturers prior to use.
Remember the larger the glass tile the longer your cure times should be prior to all foot traffic including the grouting process. Using the correct (required) adhesive is critical to the success of the installation. To highlight the importance of the recommended bonding mortars let's take a brief look at non-recommended adhesives.
Epoxy, while having tremendous bond strength, does not supply the flexibility and movement properties to make it compatible with glass, particularly in direct sunlight, therefore it should not be considered for installing glass tile. On the other hand, mastics, while more convenient for installers, have not shown sufficient bond strengths. In addition, mastics resist curing and tend to yellow behind glass tile, which can cause unsightly variations in some translucent glass tile.
We've addressed glass tile selection, substrate preparation and adhesives so let's move on to installation techniques. The most widely used notch trowel in the tile industry is the 1/4-inch-by-1/4-inch square notch trowel. This trowel works well for most large module glass tile. However, if your glass tile is thinner than 1/4-inch, it's necessary to reduce the notch size to minimize the amount of setting adhesive coming up through the grout joints yet still gauge an optimal setting bed. This concept is particularly crucial for installing thin glass mosaics.
Glass tile manufacturers recommend various techniques for installing their products. Over the last couple of years, however, we've seen more unification especially in procedures used for light bodied opaque (translucent) and clear (transparent) glass tile. Recommended installation techniques vary slightly from one glass tile manufacture to another. Please reference two field reports published by the Ceramic Tile Institute of America, available at www.ctioa.org, for the installation of glass tile. The first (2002-12-12) looks at installing large module glass tiles, and the second (2002-4-25) is for directly bonding paper faced mosaic glass tile.
Glass tile has become a highly sought after product with broad appeal because of its luminescence, depth, texture and pure color. It will continue to revolutionize our world's living spaces and to elevate the quality of tile projects as long as it is properly specified and installed.