Contractor Greg Andrews of Greg Andrews Tile -- along with Gerald Sloan, Director of Training for the National Tile Contractors Association (NTCA) -- addressed a full room about issues related to glass tile installation at Total Solutions Plus, which was held at the Sheraton Wild Horse Pass Resort in Chandler, AZ, from November 7 to 11, 2011.


During Total Solutions Plus -- held at the Sheraton Wild Horse Pass Resort in Chandler, AZ, from November 7 to 11 -- Gerald Sloan, Director of Training for the National Tile Contractors Association (NTCA), and contractor Greg Andrews of Greg Andrews Tile teamed up to present an educational seminar on glass tile installation. Among the topics discussed in the hour-and-a-half session were the differences between the three types of glass tile, installation performance, common issues faced when working with glass tile and installation techniques for glass mosaics.

The seminar kicked off with Sloan describing his first encounter with the installation of glass mosaics. “The glass was extremely expensive, very small and very thin,” he said, explaining that he soon realized that he needed assistance with the installation. “Since then, I constantly look into what is new and how we can improve on problems.”

Andrews then went on to explain the three types of glass tile:
  • Cast Glass -- Tiles are formed in a liquid state at 1,600 degrees Fahrenheit or higher. Many cast glass tile surfaces are wavy and slightly textured with inherent folds, bubbles and creases. These unique intrinsic properties are achieved through the casting process.
  • Fused Glass -- Tiles are typically made from sheet glass units that are altered through heat between 1,023 and 1,599 degrees Fahrenheit. During manufacturing, different materials and glasses are fused to the sheet glass units -- usually in multiple stages -- to create a variety of colors and patterns. Fused glass tile surfaces can be smooth, textured, uniform or non-uniform.
  • Low-temperature-coated glass -- Tiles are made from sheet glass units that are altered at temperatures less than 1,022 degrees Fahrenheit. Typically, these alterations involve heat-transferred coatings applied to the back of transparent sheet glass units. These coatings can contain wide varieties of colors and patterns.
“I know there is a lot of confusion and misinformation when it comes to glass tile,” he said. “I tell everyone it looks like tile, but it is glass. It is different than ceramic or stone. Primarily, what we see on the jobsite is Cast and Fused glass. Coating is primarily found in the decorative realm -- backsplashes and walls.”

At the end of the session, Sloan provided a live demonstration. “One thing we run into when installing small glass is that we are [often] not using the right trowel,” he said. “You want to keep thinset out of the joints.”

Installation performance

When the discussion turned to installation performance, Andrews could not stress enough the importance of referring back to the manufacturer. While EJ-171 Movement Joint Guidelines for Ceramic, Glass, and Stone -- as published in the TCNA Handbook for Ceramic, Glass, and Stone Tile Installation -- instructs that movement joints should be incorporated into all tile installations, he believes that a more stringent system should be considered with glass tile installations because glass expands at a higher rate than ceramic tile and stone.

“EJ-171 is not universal,” said Andrews. “It is not up to us to decide, but we should use common sense.” He went on to state that although many TCNA Handbook installation methods can be applicable to glass tile installation, when using these methods with glass tile, it is necessary to consider the aesthetic and performance aspects of the tiles being used. Additionally, he told the audience that when installing glass tile, the tile manufacturer should be consulted for any proprietary installation guidelines and relevant physical properties for the application being considered.

Another point to consider when installing glass tile is that with translucent glass you really can see through to the substrate. Also, glass handles less movement than other material.

Andrews also explained “Substrate Rules of Thumb,” which include:
  • The need for proper backing
  • Approved reinforcement (lath)
  • Fastener schedule
  • Proper mixtures
  • Sufficient curing
  • Crack isolation/waterproof membrane
  • Properly finished surfaces
  • Free of contaminants


Common issues

During the seminar, Andrews also outlined some common issues installers face when installing glass tile. They include:
  • Trowel marks
  • Ghosting
  • Cracks
  • Bonding issues
“Trowel marks are not only unattractive, but they can cause cracks,” he said. “[Also], a lot of times when we are cutting glass, we can pre-stress it. You might not see it right away, but a crack could show up six months later.” Andrews also went on to say that while glass is difficult to bond, it can be done.

Patience and attention to detail play a crucial role in the installation of glass mosaics. Properly backbuttering the tile is an essential technique to a successful installation.
Photo courtesy of Cipriano Landscape Design

Techniques for installing glass mosaics

When it comes to installing glass mosaics, Andrews and Sloan refer to the following standards:
  • A-108.14 -- Backbuttered over a fresh mortar bed
  • A-108.15 -- Backbuttered over a cured mortar bed or CBU
  • A-108.16 -- Thinset over approved substrate
“A misconception a lot have with backbuttering is that you think you need to fill the whole back of the tile with thinset,” said Andrews. “You should squeegee some off. Backbuttering keeps the thinset at bay so it doesn’t ooze up through the tile. It also creates a great interface between fresh thinset and fresh grout.”

Andrews brought up another commonly asked question: When do you pull the paper? “You pull the paper when it tells you to,” he said. “It depends on the temperature. It could be 15 minutes or it could be an hour.”

The discussion also touched on how to correctly apply a thinset. “Troweling is so important,” said Andrews. “What is really important is to smooth it out because trowel marks will show up. It might not be right away, but they will show up. [Also] coverage is imperative -- not just sheet to sheet, but row to row too. Smear the thinset, flatten it out and then pull the tape. Every now and then, it is good to pull up a sheet to make sure there is good coverage.”

In a nutshell, troweling techniques include:
  • Flatten out notch marks on substrate
  • Backbutter glass using a box screed for uniform thickness of thinset
  • Wiggle the glass into place using slight pressure rather than tapping on the surface


Large-format glass tiles

A glass tile that is 3 x 3 inches or larger is considered to be “large format.” “It scares me to death when I see large glass,” said Andrews. “The larger the tile, the more difficult the installation. Large tiles, when being bonded, go through expansion and can lead to problems. Every time we raise the size of the glass, we up the ante.”

Problems related to large-format glass tile include:
  • Lower impact resistance
  • Difficulty cutting
  • More sensitive to movement
  • Must be isolated from surface penetrations such as pipes, fixtures and other restraining obstacles


“I know there is a lot of confusion and misinformation when it comes to glass tile,” said Andrews. “I tell everyone it looks like tile, but it is glass. It is different than ceramic or stone.”
Photo courtesy of Modono Glass Tile

Cutting recommendations

When working with glass tile, it is important to take great care during the installation. “You have to be patient and take your time,” said Andrews. “It’s more expensive to install glass.”

He went on to say that he uses tools specifically designed for glass rather than ones for tile. “I started seeking out companies that sell tools to the glass industry,” he said. “If you go online and look up glass, you will find a wealth of companies that sell great tools.”

A few recommendations for cutting glass tile include:
  • Use blades and core bits designed for cutting glass, running at low rpm’s lubricated and cooled with water
  • Never cut square corners; always use a core bit on the inside corner of cuts
  • Hone edges with diamond pads or silica carbide sandpaper
“We cut from both sides when cutting glass,” explained Andrews. “Start at the top and go about halfway, then flip it over and go partly through the other side for a nice clean cut. If you plow through, you can explode it.”

While Andrews led the discussion on glass tile installation, Sloan offered insight and some of his own experiences with the material throughout the presentation. In conclusion, Sloan provided a live demonstration. “One thing we run into when installing small glass is that we are [often] not using the right trowel,” he said. “You want to keep thinset out of the joints.”

During the demonstration, the floor was open to questions. This gave audience members the opportunity to present problems they have run into when working with glass tile. Throughout the year, the NTCA offers educational seminars -- such as the one presented at Total Solutions Plus -- in cities across the U.S. For more information on the organization and its education program, visit: www.tile-assn.com.