High-quality mortars are the backbone of every ceramic tile and stone installation. The products we use today have several millennia of refinement behind them, providing optimal adhesion under a variety of conditions. However, despite their importance to installations, mortars have a finite realm of applicability. Installers at every experience level develop bad habits that see them using mortars to perform functions well outside this realm. Let’s look at three of the more prevalent mortar misuses and misconceptions about what they can achieve.
I can’t tell you how many failed jobs I’ve come across where the installers used mortar to fix or fill low areas under the tile. This exceeds the performance demands mortars are intended to meet. A thinset mortar is designed to have no more than a /-inch of build under the tile once the tile is beat in. When the /-inch is exceeded, you push the limits of how much the mortar will shrink during the curing process. This can cause unwanted lippage in the finished tile job. Even high-performance large and heavy tile (LHT) mortars that can have up to a /-inch of material under the tile after beaten in are not engineered to be used as a flattening agent.
Instead, many tile-setting materials manufacturers offer products especially formulated for patching and leveling. Products like Merkrete’s Pro Patch Plus will quickly and easily flatten defects from featheredge to /-inch, bringing the substrate in line with industry requirements for the chosen tile type. The flattened substrate then provides the ideal surface for the mortar to effectively bind the tile.
Another misconception about mortars is that they will automatically provide full coverage for the job. Industry coverage requirements remain 80 percent or better for dry interior areas and 95 percent or better for all exterior applications. Mortars do not magically provide these coverages. Many other factors have a direct impact on coverage.
The substrate needs to be flat. Mortars need to be mixed according to manufacturer instructions to yield the correct consistency. The installer needs to choose the proper trowel size. Larger tiles may require back-buttering to get the needed coverage. There are a variety of techniques geared to every type of installation that will help with coverage needs, so it’s essential to research industry best practices for the job at hand.
No, tile will not automatically have the proper adhesion by simply pressing it into the mortar. Installers need to key the mortar into the substrate. Then, the mortar needs to be troweled parallel to the short edge of the tile. The tile should then be placed down into the mortar and moved from side-to-side to close the ridges and allow air to escape. Once you have set a few tiles, it is always recommended to pull one up to see if you are achieving the needed coverage.
The truth is your mortar is meant for only two things: to hold the tile or stone in place and to bond to the substrate. No more, no less. There are a myriad of products available that can handle the other aspects of tiling that mortars were never designed for. These are purposely engineered to provide the ideal conditions for mortar to do its job.
That’s not to say that any mortar will suffice for every job. The tile type and project specifications can vary wildly, so it’s imperative to understand the capabilities of the materials available to you. For instance, large-format tile floor installations call for a mortar that will not create lippage from the weight of the tile. Products like Merkrete’s 720 Dustless LHT Mortar are formulated for thicker, non-slump application to minimize shrinkage during curing and help ensure tiles remain in plane.
Let’s say you want to install the same tiles on a wall surface. You’re going to want a more versatile mortar with additional properties suited to vertical installations. A mortar with non-slump properties alone will avoid lippage, but it’s not guaranteed to keep the large tiles from sliding down the wall. A mortar like Merkrete’s 820 Dustless Merlite has non-sag properties to create an instant bond that keeps tile firmly in place throughout curing. It is lighter than a typical mortar to reduce the gravitational pull on the installation while it cures.
Versatile mortars like 820 Dustless Merlite are great cost-saving, time-saving options for projects with several different types of installations. In addition to floor and wall applications of large and heavy tile, it can easily be used to bond any size tile from mosaic to thin-gauge panels. Plus, its 30-pound bag delivers the same coverage as a typical 50-pound bag, reducing wear on installers and transport vehicles.
No matter what your next project is, it’s essential to have a thorough understanding of what your mortar can and cannot do. Don’t push it to perform functions best handled by dedicated products. Consider your needs, partner with a manufacturer that anticipates them and assemble the materials accordingly.