Moisture Management

Nov. 4, 2004
Putting floor moisture problems out to dry
One of the most frustrating problems a building manager can face is debonding: the failure of a new floor system as a result of moisture problems.Unfortunately, there are rarely simple solutions to remedy this problem once the floorcovering has been installed. If left untreated, the problem can result in tripping hazards, unsightly floors, and mold growth.Often the solution to the problem involves removal of the floorcovering and application of a surface treatment to seal the floor. This can be both highly disruptive and expensive. Action taken before the floorcovering is installed is often the key to a successful installation and to avoid costly remedial measures down the road.The ProblemFloor moisture problems most often are associated with concrete slabs-on-grade (floors supported by soil). Problems most often occur with non-breathable floorcoverings such as vinyl, resin terrazzo, plastic-backed carpet, or vinyl composition tile. The primary cause of the problem is moisture vapor that emits from the concrete – it can result in debonding, bubbling, or warping of the floorcovering from moisture vapor condensing beneath the floorcovering. If a good-quality vapor barrier is used under the slab during construction, floor vapor levels normally remain at acceptable levels after initial drying.Answering the following simple questions might help you prevent problems on your next floorcovering project:

Do I need to worry about floor vapor problems with an old floor? If a non-breathable floor product (e.g. vinyl tile) had previously been installed on the floor, it is a good indicator that floor vapor may not be excessive. However, the newer water-based adhesives may be more sensitive to moisture than many of the older solvent-based adhesives. Testing should be performed well in advance of the new floor installation to determine whether floor moisture will be a problem for the new products being installed.What about installation of flooring products on a new slab? If vapor emission conditions are unknown, perform tests to assess whether floor vapor is a problem. All concrete contains moisture immediately after it is placed and will dry over time. Unfortunately, the time for the concrete to dry to a level sufficient to install adhesives may be longer than allowed by the project schedule. In some cases, it may take 6 months or more for the slab to become dry enough to install flooring products. If a vapor barrier was not installed or was damaged during construction, the floor may be too wet to accept floorcoverings.

Most floors do not have moisture problems, but the ones that do can be very costly and disruptive to remedy. Today’s new-generation adhesives are more sensitive to moisture than products used in the past. This makes evaluation of the floor moisture more important than ever for flooring projects. Always evaluate conditions prior to flooring replacement so the
project can be completed with confidence.
Mark E. Leeman, PE, is senior project manager at Facility Engineering Associates PC (, Fairfax, VA.

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