Large Format Tile & Thin Porcelain Tile (TPT) Panels
Large format tiles have been around for some time but have exploded in popularity over the past few years. Traditionally, tiles came in a relatively standard size such as 8" x 8" floor tile and 4" x 4" wall tile. Today, tiles are available from tiny glass mosaics that are 3/8" x 3/8" to large format thin porcelain tile panels that can be as large as 5' x 10'. Compared with standard tile installations, large format tiles present new challenges for tile installers. When installing large format tile, certain procedures and methods must be adhered so that the tile doesn't crack and leave behind a failed installation. Handling, lippage, subfloor preparation, mortar coverage, and curing / protection all require extra consideration during the installation process of large format tile.
A tile is considered large format when it is 16" x 16" or larger. However, a tile may also be considered large format if at least one edge is greater than 15" such as the popular wood-look porcelain planks. Large format tiles can be made of natural stone, ceramic, or porcelain with even larger, thin porcelain panels available called Thin Porcelain Tile ("TPT"). Thin Porcelain Tile panels, also called "thin tile" and "thin tile panels," is characterized by large panels up to 5' x 10' with a thickness from 3 to 6mm. Thin Porcelain Tile is not as commonly used in residential applications, but is more and more being used in commercial settings, and as with other large format tile, requires specific installation methods.
For consumers, large format tile is aesthetically pleasing with in a wide variety of colors and designs available, and as a design element, large format tiles can be used to make a smaller room appear bigger. Many people also enjoy the look of thin grout lines commonly used with large format tile. Additionally, because each tile offers more coverage per tile than traditionally sized tile, there are fewer grout lines. With fewer grout lines, maintenance becomes easier because a tile face is typically easier to clean than a grout line, and as many of us know, even sealed or epoxy-based grout can be difficult to keep clean and looking its best.
Thin Porcelain Tile ("TPT") also offers some extended benefits. Many of the Thin Porcelain Tile products on the market today are easy to clean and offer scratch, fire resistant, and waterproof surfaces. Because many are made of recycled materials, Thin Porcelain Tile is often considered a green product, and with such a thin product, less raw material is required during the manufacturing process. Additionally, the lasting durability of these products leads to sustainability, and because they are so light, less fuel is used during transportation making them a greener option compared to other tile.
With large format tile, it is imperative that the subfloor or substrate is properly prepared before laying any tile, and the larger the tile size, the more essential this becomes. It must be completely level and flat. Any dips or humps can lead to lippage that large format tile installations are prone to. Lippage is when one edge of a tile is not level with the adjacent tile's edge. This leads to the finished surface having an uneven appearance, degrades the quality of the installation, and can be a tripping hazard.
Additionally, uneven surfaces will make it difficult to achieve the proper mortar coverage and bond, another important aspect of installing large format tile. For some large format tiles, only specific substrates are approved by the manufacturer. For example, Thin Porcelain Tile (TPT) is often only approved over cement substrates.
Variance in Substrate
With traditional tile that is less than 15" x 15", there can be up to a 1/4" variance in the substrate over a 10' span. For tile with at least one edge greater than 15", the American National Standards Institutes (ANSI) recommends a maximum variance of 1/8" over a 10' span and 1/16" over a 24" span. A 6-foot level or 10-foot straight edge can be used to measure variance in the substrate. Any imperfections in the subfloor will be highlighted by large format tiles, so If the subfloor exceeds these specifications, the subfloor must be corrected with a self-leveling underlayment, patch, or grinding it down.
A self-leveling underlayment, such as
Laticrete NXT Level and Laticrete NXT Level-Plus, is a cement based product that can be poured on the subfloor to fix small imperfections in the subfloor and even out the surface. As it cures, the self-leveling underlayment produces a smooth and flat surface ready for tiling. For minor variances, a trowel applied self-leveling patch, such as Laticrete NXT Patch, can be used to bring the substrate to tolerance. Patching compounds can also be used to fix small variances on walls as well. The industry recommends using substrate preparation products and installation products from the same manufacturer to ensure compatibility.
Using the appropriate thinset/mortar is very important for a successful installation. With traditionally sized tile installations, thinset is used to bond the tile to the substrate. With large format tiles that often have a 1/4" (6mm) thickness, regular thinset can be problematic. For many large format tile installations, it is often recommended to used a medium-bed mortar to account for irregularities in the tile and substrate.
Using a thick layer of regular thinset instead of a medium-bed mortar can cause lippage or cracks because as the thinset cures, the displacement of water causes the thinset to shrink. As it shrinks and hardens, the thinset pulls on the tile and can result in damaged tiles. On the other hand, using an inadequate amount of mortar can lead to hollow spots. These hollow spots indicate that the tile is not fully supported, and the tile becomes susceptible to cracking at these points.
Medium-bed mortars are formulated to limit the amount of shrinkage during the curing process and are recommended for large format tile installations. Mortars designed for medium-beds will be able to support the tile without the tile slumping into the mortar. These mortars, however, can be difficult to trowel and work with in general. Newer types of high performance medium-bed mortars are formulated to not only be lighter, but are also much easier to trowel. When selecting a mortar, it is always advisable to consult the material manufacturer for mortar recommendations as not all mortars are suitable for every application.
Full and complete mortar coverage is an essential part of large format tile installations. Without the proper coverage, the tile and gout become susceptible to cracking along with a loss of bond to the tiles. To achieve a full coverage, start by using the appropriate trowel and troweling technique. For many large format tile installations, a larger trowel such as 1/2" x 1/2" square notch or a 3/4" x 3/4" rounded notch will help attain adequate coverage. For larger tiles, a U-notch trowel may be necessary for correct coverage.
With a correct trowel, a proper setting bed will be produced that to aid in eliminating voids and reducing time spent resetting tiles that don't have full coverage. There is no exact standard for trowel size selection, so trowel size may vary for different jobs and substrates. However, the larger the tile size, the larger the trowel that is generally needed. For instance, a 1/2" x 1/2" square or round notch trowel is commonly used for tiles sized from 13" to 20" while a 3/4" x 3/4” round notch trowel is typically used for tiles larger than 20". For thin porcelain tile panels, a specialty euro / zipper trowel is often used to achieve full coverage.
When applying the thinset to the substrate, the thinset should be combed in a linear, uniform direction. With the trowel held at a 45 degree angle, drag the trowel across the thinset in one direction leaving behind straight and full "ribbons" of thinset. Using straight trowel lines will also help prevent voids or air from becoming trapped between the tile and substrate for proper coverage and adhesion.
While a medium bed mortar will generally required for proper coverage, back buttering also helps to achieve full coverage. Back buttering is the process of using the flat side of the trowel to apply a thin layer thinset or mortar to the back of the tile before setting it. This helps to fill any voids on the back of the tile. Back-buttering is especially important with natural stone products such as travertine, granite, marble, slate, etc. because of the naturally occurring spaces and imperfections on the back of the tile. By filling the spaces in with thinset before setting, weaker areas are strengthened and better coverage is obtained.
For thin porcelain tile panels, a different method is used for back buttering. Instead of using the flat side of the trowel to produce a flat even coat on back of the tile, the notched side of the trowel is used to create the same ribbons of thinset as used on the substrate. These thinset ridges should be in a level line across the back of the panel and will line up parallel with the ridges of thinset on the substrate. By troweling the both the backside the panel the same as the substrate, 100% coverage can be achieved which is essential for the success of thin porcelain panel installations.
Large format tiles are more susceptible to cracking than smaller sized tiles. Movement along with tiny cracks in the subfloor can transfer to the tile and result in cracks. Traditionally, reinforced mortar beds had been used to allow the substrate and tile covering to move independently of each other and prevent the transfer of cracks from substrate to covering. However, reinforced mortar beds add a significant additional height to the installation and isn't practical by today's standards for new construction and remodels.
Uncoupling membranes are designed to replace the traditional reinforced mortar beds without the addition of significant height. While each manufacturer will have their own design, in general uncoupling membranes are composed of a waffle-like grid structure with an anchoring fleece on one side, are light weight, come in a roll, and are easy to install. Incorporating an uncoupling membrane or other crack isolation underlayment will help to prevent cracks from occurring.
Even with a perfectly flat subfloor, lippage is still another concern for large format tile installations. Lippage occurs when the adjacent edges of two tiles are not even. The bigger the tile, the more problematic lippage can become. Not only does lippage appear more prominent with larger size tiles, it also is presents a greater tripping hazard. Incorrect mortar bed, wrong setting techniques, and warpage can all lead to lippage.
Using an appropriate sized mortar bed, such as a medium-thick mortar bed, with correct setting practices will help to prevent lippage. Another extremely valuable tool available today are tile leveling systems. Both Tuscan Leveling Systems and MLT Leveling Systems are easy-to-use tile leveling systems that will greatly help in creating lippage-free installations. These systems generally consist of a few components including base/bottom plates, caps, straps, and installation gun and can be used for both floor and wall applications.
Tuscan Leveling System
Tuscan Leveling System is a 3 component tile leveling system including straps, caps, and installation tool, and can be used with grout joints down to 1/32". For wider grout joints, common tile spaces can still be used with the leveling system. The small, square foot / bottom plate attached to the end of each strap is slid under the edge of the tile 2 -3 inches from each corner. The cap then slides down over the strap and will sit on the top part of the tile. With the strap and cap in place, the Installation Tool is used to tighten down the assembly, locking all the tiles in place for a level and flat surface.
Both a Manual and Ergonomic Installation Tool are available with the Tuscan Leveling System. The Ergonomic Installation Tool allows the installer to adjust the tension of the tool by rotating a knob on the tool. The ability to adjust the tension is beneficial when doing large installations and also allows for a higher tension when setting large format tiles. The Manual Installation Tool does not allow for the tension to be adjusted.
To speed up the installation process, the straps and caps can be pre-assembled with a 1-1/2 - 2 inch gap left between the strap bottom plate and cap. Each assembly can then be quickly put in position on the tile and tightened. Once the setting material has properly cured, the straps are removed by snapping them off at the breaking point with the Installation Tool. While the caps can be reused around 25 times, the straps are single use.
Tuscan Leveling System - SeamClips
A new, single component leveling system from Tuscan are the SeamClips. The Tuscan SeamClips are an innovative and easy-to-use leveling system that is a single piece and doesn't require any tools. The SeamClips work great for lippage-free installations of natural stone, porcelain and ceramic tiles, large format tiles, and thin porcelain tile panels. To accommodate tile ranging from 1/8" to 3/8" thickness, 3 different type of Tuscan SeamClips are available including Red SeamClips, Blue SeamClips, and White SeamClips.
Because each Tuscan SeamClip is a single piece, they are designed to be used only once and don't have any replaceable parts like the traditional Tuscan Leveling System. This makes them an easy and cost effective solution for small, one-time jobs. However, their ease-of-use and economical price point also make them a good solution for tile installers that don't mind purchasing them for each job. To use, simply slide the base under the tile and close the wings down to create a level surface. Once the installation has cured, a rubber mallet is used to remove the top portion.
MLT Leveling System
MLT Leveling System consists of 4 individual components including bottom plates, straps, caps, and an MLT Removal Tool and can be used with tile from 12 " x 12" up to slabs 3/4" thick with grout joints down to 1/64". The bottom plates are separate from the straps and are available in different options for different types of tile including porcelain, thin tile, slab, and plank/offset. This gives the installer the versatility to choose bottom plates most applicable for their tile installation. Because the straps are separate from the bottom plates, the straps are reusable.
Like other tile leveling systems, the MLT Tile Leveling System also utilizes caps. While the caps can be used over a 100 times, a Steel Tongue Insert is an optional cap accessory that will help extend the life of the caps even further. Another optional accessory for caps are Rubber Feet to prevent the cap from scratching the tile. The Rubber Feet are valuable when working with delicate and easily scratched tile.