Technical Focus: Flatness Tolerances, Self-Leveling Underlayments and Radiant Uncoupling Mats
Flatness of the substrate or underlying structure has been and always will be paramount to the flatness of the finished flooring system, regardless of the type of flooring materials used. For years, smaller-sized tile enabled contractors to build under flooring during installation as needed in small areas to make up for non-flat substrate surfaces. As tile modules have evolved into large-format porcelain tiles and gauged porcelain tile panels, the flatness tolerances have become a key point of focus from both the tile manufacturers and installation systems companies.
The tolerances are, in fact, requirements for a beautiful and durable tile assembly. Ensuring a properly flattened substrate before the installation of tile finishes is now mandatory. Larger tiles simply cannot be installed as smaller tile bodies have been historically. Without the appropriate tolerances, floor installations can have many issues and failures that undermine long-term performance. This can result in lippage problems for porcelain tile installations and adjacent vinyl flooring can become excessively worn or torn at seam interfaces.
Radiant uncoupling systems are not for use exclusively with porcelain tile or stone finishes. These systems can support a variety of floor finishes, but cannot repair any deficiencies in flatness tolerances in the substrate. A traditional approach would require installing repair materials first, allowing them to dry, and then installing the uncoupling mat. Now, there is a new approach due to technological advancements in cement repair materials. This allows installation of the radiant uncoupling mat first, then flatness tolerances can be achieved by the installation over the mat system.
What’s the benefit to this approach? First, less repair material will typically be required to achieve flatness, with no wait times between prep and mat installation, as well as the ability of the installation contractor to manage final elevations at the top of the system versus prep below and final projections above. Second, using a self-leveling underlayment (SLU) will require the use of a primer over the substrate before installation. This is not necessary when using a high flow product such as TechLevel™ WSF Fiber Reinforced Self Leveling-Underlayment that has been designed for use over wood subfloors and other challenging substrates. Placement of an appropriate SLU over a radiant uncoupling mat can save significant time and money. Lastly, there is the advantage of having the radiant uncoupling system throughout the entire flooring assembly regardless of the floor finishes specified — whether carpet, vinyl, wood and/or tile — all on one flat plane.
Applying a cementitious SLU over an uneven substrate is the most efficient way to achieve a smooth, flat surface. This is critical for successfully installing ceramic tile, natural stone, terrazzo, vinyl and other demanding floor coverings. While preparing many substrates for leveling is relatively simple and straightforward, plywood and oriented strand board (OSB) subfloors typically must be reinforced with metal lath. Now, self-leveling technology eliminates the time-consuming and labor-intensive process of attaching metal lath to wood subfloors. This makes floor covering installations faster, easier and more profitable.