Concrete moisture is the number one cause of flooring failure and accounts for approximately $3 billion of loss annually. Liability exposure for moisture-related flooring failures may extend to several members of the construction team, including the flooring contractor, general contractor, flooring and adhesive manufacturers and the project specifiers.*
In the early life of the concrete slab, water is used in the hydration of the cement to produce high-quality concrete. Excessive water, water not used in the hydration process, is used to make the placement of the concrete easy. During the evaporation period, concrete must give up most of the excess water to become suitable for impervious and low permeability flooring systems.
Flooring such as sheet vinyl, vinyl composition tile, and polymer coatings and surfacing systems are referred to as impervious or low permeability. These flooring systems are very dense and do not allow for passage of moisture. When impervious or low permeability flooring is installed over portland cement concrete with high moisture content, this moisture will migrate upward through the top of the concrete slab, carrying dissolved alkalis inherently present in the concrete. These alkalis can destroy the bond between the concrete and the flooring materials. The alkalinity will become concentrated and this moist, high pH environment at the bond line can cause failure. This failure may be evidenced by disbonding, adhesive breakdown, osmotic blisters and staining. The excessive moisture may also allow for microbial growth with the related reduction in indoor air quality.