Mark Pennine, Ardex technical manager, recommends the use of a pourable mortar in thin and large-format tile installations. “A pourable mortar allows the installer to achieve proven 95 to 100% coverage on the back of the tile when installing over a flat and smooth floor surface that was prepared using a self-leveler.”
He noted that subfloor preparation is even more crucial with these types of specialized tile products. “Self-leveling underlayment will help create a smooth substrate. Additionally, preparing walls to make plumb with a screeding and smoothing mortar ensures a properly prepared surface for any tile installation.”
According to Dan Marvin, MAPEI director of technical services, one of the problems with thin tiles is there are no industry standards for the products yet, so “thin tile” may mean something different from one manufacturer to another. “The U.S. tile industry has put out a joint statement saying the minimum thickness for a floor tile should be 5.5mm (around 1/4”), but some manufacturers continue to allow tiles as thin as 3.5mm (1/8”) on floors. As tile gets thinner, there is less margin for error in installation and the products you use to install the tiles.”
He said to ensure full coverage of mortar on the back of the tile, choose a polymer-modified mortar that flows well but is thixotropic. “Thixotropic mortars (look for a ‘T’ rating in the ISO or ANSI code) go from fluid to stiff quickly once you stop troweling them. Trowel the mortar on both the substrate and the back of the tile in parallel lines with a ‘euro-notch’ type of trowel designed to let the trowel ridges collapse easily. When the tile and the substrate come in contact with one another, add some energy to fluidize the mortar and work the air out. We recommend an orbital sander with a rubber pad, starting from the center of the tile and working to the edges.”
Minimizing lippage—a common problem in thin-tile installations—requires a very flat subfloor and the use of a mechanical lippage system, he added. “There are several of these available on the market but find one that allows you to clean the mortar out of the grout joints before it cures. Grouts should be either epoxy, a high-end cementitious grout or one of the new ready-to-use grouts depending on the service environment. Because of the size of these thin tile panels, it’s important to follow industry standards (EJ171) for the width of grout joints and the inclusion of soft joints.”
Marvin commented that thin tile panels are often flexible, with a reinforcing fabric on the back. “Make sure the setting materials you use can flex and are compatible with the backings. We have been testing thin tile systems on our Universal Floor Tester and have found they work well over a variety of solid substrates but aren’t the best choice for use with a thick membrane. Roller-applied membranes tend to yield better results than thicker sheet membranes in high traffic areas.”
QEP’s Brad Miller, vice president of product management/development, said installing larger and thinner tile has led to manufacturers modifying some tried-and-true tools. “Trowel notches have been modified with varying depth for installation of thin tile, along with deeper, thinner grooves versus a standard square or U-shaped consistent notch. Special cutting systems have been designed due to the longer length of thin tile and how fragile it can be. Double and triple suction cups are being used to help installers move and place these larger and heavier tiles.”
Art Mintie, Laticrete’s director of technical services, said medium-bed mortars are ideal for large, heavy tile as they can support the weight and be built up to thicknesses of up to 1/2” and even 3/4” in some cases. “Mortars that have long open and adjustability time are ideal for large thin porcelain tile as more time is required to apply the adhesive mortar, place the tile, adjust it and then properly embed it. These mortars also require the ability to ‘wet out’ the substrate and the back of the large tile while being able to ‘collapse’ properly to achieve the maximum amount coverage possible.”
He also recommends knowing the proper tools and staging equipment for these types of installations. “This would include a table where cutting can take place, forklifts that can move the crates around, wheeled staging frames where the tiles can be relocated as required and access to a large enough elevator if the tiles need to be moved to upper floor areas. The use of setting frames, suction cups, large rail cutters, handheld vibrating pads and other specific equipment will make the project installation successful. The use of the proper trowel type (typically a slant notch or special euro notch trowel) and mechanical edge leveling system will help achieve the proper coverage and prevent lippage.”
Regarding subfloor flatness, he points to Tile Council of North America (TCNA) recommendations. “When tiles have at least one edge that is greater than 15 inches in length, the maximum allowable variation in the substrate is 1/8” in 10’ from the required plane, with no more than 1/16” in 24” when measured from the high points in the surface. The use of crack isolation membranes can also be helpful in preventing existing or potential future non-structural cracks in the substrate from telegraphing through the tile layer,” Mintie noted.
According to Michelle Swiniarski, Bostik’s ceramic installation systems market manager, depending on the tile type, scoring and cutting can be difficult and lead to an uneven edge. “It is best to invest in a premium-quality wet saw and take your time while making the cut. While drilling, it may be best to use cool water, especially with porcelain, to avoid cracking.” A best practice she recommends is to order extra tile to compensate for cracking and rough cuts.
When working with mortars designed for heavy and large tiles, be sure not to overwater the mortar. “This may lead to the tile shifting and sinking into the mortar, causing lippage and reduced physical characteristics of the mortar. Care must be taken to key the mortar into the substrate prior to troweling the mortar in a straight, parallel line and install perpendicular to the ridges so an adequate bond may be achieved.”
Swiniarski noted to consider the size of the grout lines, which will be different for natural, calibrated and rectified tiles. “It is also frequently necessary to wait a longer amount of time for the mortar to set, as the larger tiles and thicker application of mortar may extend the drying time before grouting to avoid efflorescence.”
Steve Taylor, Custom Building Products’ director of technical and architectural marketing, said to choose a large-format tile mortar with extended opening time. “Mortars designed with an extended open time give the installer the flexibility needed to get the tile positioned and obtain a good bond. Specialized mortars for floor applications have been designed to flow and fill in the ridges under the tile.”
It is also important to use the specialized tools developed specifically for large and thin tiles. “Specialized trowels deliver the best mortar coverage and ridges to promote full coverage. Other tools have been also developed to handle very large, 3’ by 10’ tile. They are critical for moving these tiles into place without damage. Once the tile is back-buttered with mortar, it can be difficult to pick and place on the substrate. Special frames simplify this process. There are also new tools for cutting these large tiles. Mechanical edge control systems are almost mandatory with these large-format tiles to minimize lippage.”
He also commented on the importance of using a crack isolation membrane. “The very thin tiles, less than 5.5 mm thick, have a lower breaking strength and the industry is advocating the use of membranes. The soft membranes may not support the tiles adequately and cause cracking. We advise testing any tile and membrane combination with the Robinson Floor Tester.”
Tom Plaskota, Tec/H.B. Fuller Construction Products’ technical support manager, stated many manufacturers apply mesh backing to large, thin tiles with an epoxy or other resin-type adhesive. “Resin backing minimizes the breaking of thin-cut fragile stone, but can present challenges to installers seeking a strong bond. Selecting the right setting material allows installers to realize the benefits of resin backings, while achieving a strong bond.”
Look for setting materials that have not only good bond strength but non-sag capabilities for walls and non-slump characteristics for floors. “With large, thin tile, it is important to use materials with high resistance to shock and impact, and that have the compressive strength to support the panels. Mortars should also have medium-bed characteristics to control the amount of shrinking that occurs during the curing process.” He added that strong, durable grouts are essential.
Here is how he recommends setting up the crew. “The largest of these tiles – up to 10 feet long – must be handled by at least two people. Once installation begins, one person will mortar the substrate, while another simultaneously back-butters the tile. To keep pace, at least one more individual will continuously mix and maintain the flow of mortar. Even the smallest installations of large, thin tile require a crew of at least four people.”
Special handling equipment is also required. “To prevent damage from occurring during forklift operation, specific fork sizes must be used. For example, to handle a crate of 3’ by 10’ tiles from the side, 44” long forks are recommended. Handling the same crate from the narrow end requires forks that are at least 84” long. Lifting multiple crates with longer forks may require forklifts with a greater lift capacity. Be sure to have the appropriate forklift on the job site.”
Plaskota added, “Two installers should handle each large porcelain panel, always keeping it perpendicular to the floor and protecting its corners from impact. If the panels have fiberglass backing, use gloves to avoid hand irritation. When unloading, position each porcelain panel on its long side. Lean the slabs against a supporting wall, while keeping cardboard or wooden strips suitably spaced beneath them.”