Did you know that gauged porcelain tile/gauged porcelain tile panels and slabs (GPT/GPTPS) were originally developed to be used as a veneer to cover aged and damaged marble on buildings in Europe following World War II? According to Sam Biondo, Jr., national technical presenter, MAPEI, many of the buildings were built in the 1940s and 1950s, using two-inch thick, 10’x4’ marble slabs. 

The dilemma was to destroy the age-old structures or to simply cover them up. It was up to porcelain manufacturers to find a solution. The result: 5’x10’ and 5’x12’ porcelain tile veneers—the precursor to today’s GPT/GPTPS. 

GPT/GPTPS for walls and floors range in thickness from 3mm to 6.5mm. GPT slab thickness for flooring applications ranges from 5mm to 6.5mm. Anything over 7mm is considered standard body tile. What’s the difference? GPT/GPTPS are manufactured using less material than standard body tile to create a lightweight option in a large format. The manufacturing process requires less energy, making them a more “sustainable” option, according to MAPEI’s reference guide on “Gauged porcelain tile panels/slabs—floors.” Special handling techniques must be used to maneuver the thinner format to prevent damage prior to and during the installation process. 

MAPEI hosts trainings on GPT where Biondo and other trained tile professionals teach students everything from industry standards to material handling to tool requirements to proper surface prep prior to installation. Here, we will focus on how to prep a slab for floor installation and how to properly maneuver it. There’s more to it than you would think! Bear in mind that the training is a simulation, using smaller pieces of slabs and a pre-built module that meets the proper flatness specification.

Ready, Set, Go

After all the necessary preparations have been taken to ensure your workspace has been secured and cleaned and the slab has been safely delivered and placed in the prep area, you must make sure all of your tools and supplies are accessible and ready to go. For this application, MAPEI’s Keraflex Super Large-and-Heavy-Tile Mortar is being used. Keraflex Super is designed for wall and floor applications.

Step One

In preparation to move the tile from the “crate” to the work surface, wipe the top surface of the slab with a damp sponge, removing any dust or residue.

Gerald Sloan, technical services representative, MAPEI uses a sponge to clean the tile. Photo: Floor Trends & Installation.

Step Two

Dry excess water prior to applying suction cups.

Dave Moore, technical services representative, MAPEI, uses a microfiber towel to mop up standing water. Photo: Floor Trends & Installation.

Step Three

Apply suction cups ensuring that all water has been removed and the suction cups are secure. Suction cups are ideal for the smaller slabs. “Anything larger than this requires a frame where you’ll see the suction cups made on the frame,” said Sloan.

Moore demonstrates application of two different types of suction cups. Photo: Floor Trends & Installation.

Pro tip: According to Sloan, “handle [the slab] as though you are handling glass.” Using the appropriate tools means using high-quality suction cups. He warns installers to limit the number of times your hands touch the tiles. When shopping for suction cups, he advises looking for something with a suction indicator to let you know that they are functioning properly. Moore adds that keeping the suction cups clean and protected is imperative to the life of the suction cup. “As soon as I’m done with those cups, at my first opportunity, I put those covers back on the suction cups,” he said.

Step Four

Coordinate the handling of the slab. This means not only talking through the liftoff, but it also means being careful with foot placement and hand placement as you make your way to the prep area.

From left: Moore and Sloan pause to shift hand placement. Photo: Floor Trends & Installation.

Step Five

Place tile on work area. According to Sloan, one meter by one meter or larger slab requires a minimum of three people to maneuver the tile. Two people are needed to handle the tile and one person must act as a spotter, overseeing the path the slab and handlers travel, watching for trip hazards, and in this instance, ensuring the sawhorses are centered.

Chad Loveless (center), sales representative, MAPEI, acts as the spotter, checking the sawhorses to make sure they are in the correct place. Photo: Floor Trends & Installation.

Step Six

Use a damp sponge to remove the kiln release from the backside of the tile in preparation for the Keraflex Super. Failure to remove the kiln release can cause bonding issues. Kiln release is exactly as it sounds. It is a refractory material that is applied to the backs of tiles to prevent them from sticking to the kiln rollers.

Sloan using a damp sponge to clean the backside of the tile. Photo: Floor Trends & Installation.

Step Seven

Use the correct trowel. Using a conventional trowel, like the one Sloan is pointing to, will be a challenge to get the appropriate coverage. Instead, the Euro/Slant ridge trowels that Moore is holding are what is recommended for this application.

A ½”x ½” trowel is not recommended for GPTPS mortar application. Photo: Floor Trends & Installation.

Step Eight

Trowel the tile before the substrate. “I always choose the tile,” Sloan said. “It’s going to be less absorbative, so you will end up with a lot longer open time.” Open time is how long the mortar retains its ability to bond to tile after being applied. Be sure to hold the trowel at a 45-degree angle and once the tile is completely back-layered with the Keraflex Super, trowel outward from the middle.

Keep the trowel strokes consistent. Photo: Floor Trends & Installation.

Step Nine

Assuming you have tested your substrate for absorption (one drop of water for one minute) and the drop was absorbed, use a damp sponge to clean the substrate. Trowel the Keraflex Super on to the substrate. Sloan points to the ANSI A108.19 Interior Installation of GPT and GPTPS standard 13.8. It states, “Overspread the mortar on the substrate by at least an inch wider than the gauged porcelain tile or gauged porcelain tile/slab you plan to embed.” This is to ensure full support of mortar at the tile edges and corners.

Notice the troweling on the substrate is from the center outward just like on the slab. Photo: Floor Trends & Installation.

Step Ten

Maneuver the slab and place. Each step is exactly the same as moving the slab from the “crate” to the sawhorses only in reverse. Communication between tile setters is imperative. Use the spotter to help look for trip hazards and keep the slab lined up with the mortar.

(Left) Sloan, (Center) Loveless and (Right) Moore work together to place the slab. Photo: Floor Trends & Installation.

“The intent here is to show you that it's not difficult to install GPT,” said Sloan. “It's just cautionary, but once you get the feel for it and understand the parameters of what could go wrong and how to avoid it, then you can be very successful with it.”