For flooring professionals, surface preparation includes a wide array of products and methods comprised of self-leveling underlayments, mortar beds, waterproofing/crack isolation membranes, patching and repair products, moisture mitigation membranes, crack repair, diamond grinding, shot blasting and scarification, just to name a few. The first step in a good surface preparation process is to conduct a full and thorough evaluation of the substrate to determine which of these products and methods, and how many, are needed.

Moisture mitigation membranes

Excess moisture in concrete is the leading cause of floorcovering failures. In North America alone, it has been estimated that the cost of floorcovering failures due to excessive moisture vapor emission from concrete floor slabs exceeds $1 billion per year. Fast-track construction practices and speedy return-to-service/turnaround time requirements have also contributed to an increase in concrete floor slabs not having a sufficient amount of drying time.

While excess moisture is a well-known issue in the flooring industry, concrete moisture conditions are often not measured or dealt with properly. When moisture-sensitive flooring products are installed, the excess moisture vapor in the concrete causes a highly alkaline condition at the bonding interface between the concrete and the floorcovering, attacking and weakening the adhesive, which often times leads to costly flooring failure. Most, if not all, moisture vapor related failures could be prevented by installing a moisture mitigation membrane prior to installation of the flooring products.

Moisture mitigation products are typically two-part, liquid-applied epoxy membranes applied in a single coat using a notched squeegee to gage the mil thickness. Moisture mitigation membranes, not to be mistaken with waterproofing membranes that are designed to prevent liquid water from penetrating into a substrate and leaking into occupied space below, are specifically designed to control the moisture vapor emission rate from concrete floor slabs. The use of a moisture mitigation membrane allows for the installation of moisture and pH-sensitive stone, tile, vinyl, rubber, resinous and other types of flooring.

Self-leveling underlayments, mortar beds and patches

Typically comprised of Portland cement, aggregate, polymers and “other ingredients,” self-leveling underlayments, mortar beds and patch products are used to fill in, flatten and provide a hard, smooth surface for bonding to the floorcovering. While the different products are similar in composition, it is the “other ingredients” that give each of these products specific performance and working properties, catering to various conditions, which may present during surface preparation or flooring installation. For example, a fast-setting patch may be needed to repair an area that is scheduled for a flooring installation the same day. Or, a flowable self-leveling underlayment may be needed to flatten and smooth a very large area that can be walked on a few hours after install. For projects that have large areas where a ramp or slope is needed, mortar beds are well suited, while a self-leveling underlayment is too fluid to create a slope or a ramp. Additionally, there are patching and repair products that can be ready for finished flooring in minutes. These are usually two-
component resinous products — epoxy or polyurea — which are typically mixed in small batches.

No matter what condition you may be faced with, there is a very good chance that there is a product available that was designed for that exact condition.

Waterproofing, anti-fracture and sound control membranes

Tile and stone installation membranes can be liquid-applied in a similar manner to paint, the most common application, or sheet-style. It is important to note that some membranes perform as waterproofing and anti-fracture membranes, while others will function as anti-fracture membranes and not waterproofing. Additionally, some waterproofing and/or anti-fracture membranes will function as a sound reduction product. Most liquid-applied membranes are painted on in multiple coats using basic tools, paint rollers and brushes at a specific thickness according to the manufacturer’s instructions.

Sheet membranes are installed using a suitable thinset adhesive, which is troweled onto the substrate then pressed into the adhesive, sometimes with the use of a weighted roller for floor application. These types of membranes are typically thicker than a liquid-applied membrane and offer waterproofing, crack isolation and sound reduction properties.

Sound reduction membranes are mostly sheet-style goods that are installed directly below the tile installation. Sound control membranes are available in a peel-and-stick design or via a sheet membrane that is glued to the substrate using a tile adhesive. The tile is then bonded directly to the sound control membranes. This style of membranes works by absorbing the impact of vibration like footsteps, reducing the amount of noise that will transfer to the rooms below.

Membranes vary greatly in specification, installation, performance and function from different manufacturers. Consult the installation guidelines from each membrane for details and instructions.


Always consult with the floorcovering and adhesive manufacturer for requirements regarding the level of surface prep, limitations on moisture conditions, compatibility with underlayment products, etc. Properly addressing all potential substrate issues will greatly minimize the risk for costly finished flooring issues down the road.