Dec. 9/16 2013; Volume 27/number 16
By Gary Liddington
Moisture problems are the bane of anyone associated with flooring installation, and the battle begins long before the first plank, tile or sheet is actually installed. The opening salvo is proper subfloor preparation, pure and simple. No one would paint her house over existing chipped and peeling paint, so why would anyone embark on an installation of quality flooring without ensuring the surface is properly prepared and within well-established moisture limits?
The instructions for most flooring installations require the subfloor to be clean, dry, flat and free of any contaminants. It is well established that it normally takes about 30 days to dry one inch of concrete, so a 3- to 4-inch slab will need three to four months to reach a reasonable level of dryness. However, in this current age of fast-track construction, this time frame is rarely allowed, and the resulting moisture conditions can be quite detrimental to flooring installation. There are plenty of excuses for the lack of proper subfloor preparation, but they don’t come from a true flooring professional.
Subfloor moisture always exists at some level, regardless of the age of the floor. Failing to address it is a sure recipe for disaster that someone is going to have to pay for. The beginning step of any flooring installation must be the determination of how much moisture has to be removed. The most common methods of measuring subfloor moisture are the calcium chloride test and the relative humidity test.
The anhydrous calcium chloride test is performed in accordance with the ASTM F-1869 test method and the relative humidity test with the ASTM F-2170 test method. The calcium chloride test measures the rate of moisture emission and the relative humidity test measures the amount of moisture present in the floor. Regardless of the method used, these tests must be run in complete compliance with the test methodology. Ignoring the directions on measurement in an enclosed, acclimated installation jobsite only negates the accuracy of the readings. Sometimes people claim that they cannot afford the time to run the moisture tests properly or at all; the truth is that you cannot afford to not run moisture tests.
If moisture readings are within the established limits, the likelihood of a successful flooring installation is greatly increased. However, recognizing that there isn’t complete certainty when it comes to moisture and its measurement, the flooring adhesive industry has long been proactive in developing products that are either more tolerant of moisture or offer varying levels of remedy to subfloor moisture situations.
Adhesives featuring advanced cross-linking properties that result in waterproof bonds are very resistant to moisture in subfloors; however, this protection is limited to the adhesive itself. A crosslinking adhesive that is troweled down for flooring installation will allow moisture movement between the trowel ridges. Although the cured adhesive is largely unaffected by existing moisture, the installed flooring itself is subject to moisture exposure and deterioration. In order for an adhesive to assume some measure of protection for the flooring, it must be applied so as to become a homogeneous membrane over the subfloor.
The top products offering moisture inhibition are those that are multi-functional in terms of providing installation bonding and moisture retardation, as well as sound deadening properties and concrete subfloor crack isolation. For example, W.F. Taylor has developed multi-functional adhesives based on modified silane (MS) polymer that offer floor adhesion, very low perm ratings, sound suppression that meets or exceeds major building codes and provide concrete crack isolation.
Perm ratings are a measure of the adhesive to inhibit moisture, and the lower the rating, the greater the ability to retard moisture movement.
As long as water is used to make concrete, there will be moisture problems to contend with in concrete subfloors. There is no substitute for proper subfloor preparation, but the innovations of flooring adhesive manufacturers provide additional tools.