Moisture-related floor covering and coating problems have in recent years become among the most common and costly issues being faced by design professionals, contractors, manufacturers, installers, and building owners. Each year, such problems account for hundreds of millions of dollars in unanticipated expenses to correct problems and resolve disputes.

Here are some commonly asked questions on this issue.

Question: Why does it seem that moisture-related flooring problems are more common today than in the past?

Answer: Moisture-related problems with flooring materials installed over concrete slabs are not new and have been around since the earliest days of flooring installations. However, the magnitude and frequency of such issues does appear to be more prevalent today.

There are a number of reasons why moisture-related flooring problems are so common today. First, we live in a fast-track world where construction schedules often do not provide sufficient time for concrete to dry naturally to a level acceptable for the installation of flooring or coating materials.

Second, it is all too common for below-slab moisture protection to either be omitted from the building design or for the materials used to provide a less than adequate protection, be installed improperly, or compromised during construction.

There are several other factors, such as the change from solvent-based to water-based adhesive formulations and the widespread use of curing and bond-breaking compounds.

Question: Where does the moisture come from?

Answer: The first moisture that is a challenge to any new flooring installation is free water within the concrete itself. Free water, or water of convenience, is that water above what is absolutely necessary to hydrate the cement particles and brings a concrete mixture to a workable consistency for placement. Free water does not combine chemically in the hydration process and is present within the concrete paste, aggregate particles, or within capillaries or pores of the concrete.

The second source is moisture rising from below the slab. If an effective, low-permeance vapor retarder material is not installed directly in contact with the underside of the slab, the concrete will be exposed to a perpetual source of moisture rising from below. Without an effective vapor retarder below the slab, the flooring material becomes the stopping point for rising moisture, setting the stage for problems to develop.