Uses of Mortar: Can Mortars be Used to Patch or Level an Uneven Concrete Floor?

The title of this blog is a frequently asked question that tile installers have considered when a concrete or plywood substrate dips or humps in the floor. Because mortar will stick to the concrete slab and the wood subfloor, and mortar will stick to mortar, then it would only make sense that mortar would work for leveling or patching concrete or wood floors, right? Well, the answer is actually no.

Mortars cannot be used to level or patch an existing concrete floor – ever! The materials used in mortars are different from self-leveling concrete and self-leveling cement. They render the product unstable once the thickness exceeds the manufacturers’ recommended maximum thickness.

Most thin-set mortars have a maximum thickness of 1/4" (6 mm) and medium-bed mortars have a maximum of 1/2" (12 mm). So of course, the next question is, “What if it is done in layers?” The answer again is no. Once the mortar is cured, each new layer becomes one with the previous layer; this makes the mortar unstable once curing has occurred.

Now that we have established that mortars won’t work for leveling and patching, what can be done with a dip or a hump in the substrate? We recommend choosing a self-leveler or patch product instead.

High-Quality Self-Leveling Compound Options

MAPEI makes several different levelers and patches to accommodate a variety of issues that an installer may encounter with concrete floors or wooden floors as substrates on a tile-installation project. The most versatile self-leveler is Novoplan 2 Plus, a high-strength, cement-based underlayment and repair mix for use over traditional concrete, plywood and other approved interior floor surfaces.

For smaller issues that only require patching and not necessarily the need to level an entire area, MAPEI makes a product called Planipatch, an ultra fast-drying, self-curing, polymer-modified, cement-based patching compound that rapidly develops high compressive strength. It can be used to fill minor voids, holes and cracks in various types of prepared floors, such as cement terrazzo floor, a wood floor, a garage floor or other concrete surface.

Novoplan 2 Plus and Planipatch are easy to use, work exactly as a self-leveling underlayment and patching compound respectively should, and are readily available at a local distributor in your area. Every installer should have both a concrete leveler compound and patching products ready to go when starting a new interior flooring project for a customer.

Get Helpful Tips on Tile Installation and Floor Leveling

Looking for more tips for tile installation or other floor coverings? Visit our System Solutions portal here. At MAPEI, we believe that preparation and execution go hand in hand to obtain the best possible solution to any situation.