Understanding Floor Moisture Mitigation – Construction Canada


By John T. McGrath, Jr.

When it comes to flooring specifications, understanding proper moisture metering, mitigation, and proper floor preparation will protect against the costly pitfalls of commercial construction. Specifying industry-recognized practices will protect against disruptive corrective action. Besides cost, moisture-related flooring failures cause disruptions large enough to shut down building operations, resulting in lost revenue, health and safety hazards, and unhappy customers.

During soil preparation and moisture testing (including ASTM F1869-16a, ASTM F2170-19aand ASTM F710-19e1) have become common practice, these critical steps can be overlooked due to tight deadlines, limited budgets, inexperienced contractors, uninformed specifiers, or installation crews that lack proper training. The result can be a plethora of flooring problems appearing days or weeks after a floor is installed, including adhesive breakdown, bubbles, suction cups, gaps between tiles or planks. and mold conditions.

For these and many other reasons, it is essential that architects, designers and other specifiers understand the root causes of moisture-related flooring failure, the importance of ordering standardized moisture testing and the roles of site readiness assessment reports and pre-construction meetings. in the process of preparing the floor covering. It could mean the difference between their next success or a black mark on a company’s reputation.

Advanced Testing Standards

Most resilient commercial flooring designs install over a concrete slab subfloor. Newly poured concrete slabs often take weeks or months to harden, slowly releasing moisture as they dry. When resilient, non-permeable flooring systems are installed prematurely, they fail due to evaporation of moisture rising to the surface of the slab.

These moisture problems are only exacerbated by extreme cold, high humidity, and other environmental conditions. In many Canadian provinces, daily high temperatures rarely exceed freezing from November to April. Combined with heavy snowfall and high humidity, concrete slabs in unconditioned spaces can freeze quickly, affecting the strength of the concrete.

As a result, the American Society for Testing and Materials (ASTM) has developed standard practices for moisture testing and mitigation, and well-trained and certified flooring contractors are putting them into practice across the country. .

ASTM F1869-16a is an anhydrous calcium chloride test covering the quantitative determination of the rate of water vapor emitted from the concrete substrate over time. The relatively simple test involves sealing a small dish of calcium chloride onto a clean section of concrete under a plastic dome. The salt absorbs moisture in the localized environment and the weight gain after three days plugs in to calculate the water vapor emission rate (MVER).

While ASTM F1869-16a tests the surface of a concrete slab, ASTM F2170-19a goes even further. This in situ relative humidity (RH) test provides the quantitative determination of the relative humidity present inside a concrete substrate. It formally recognizes the use of in situ probes as a means of performing relative humidity testing and, at the time of its adoption, represented a fundamental change in the way humidity was measured in subfloors, as well as in the degree of accuracy of information that testers could obtain from relative humidity meters.

In-situ probes measure moisture content deeper in the concrete matrix, while calcium chloride only tests the surface of the slab. Each probe or sensor requires a hole measuring 19.05 mm (0.75 in) in diameter and at a depth equal to 40% of the slab thickness for slabs drying on one side, or 20% deep for a slab drying on both sides. The probes can also remain in place for weeks to determine if there is a change in humidity levels.

When testing, it is also crucial that installers consult flooring product manufacturers, as surface preparation requirements and methods vary depending on the type of substrate, subfloor, underlayment and of flooring specified.

For example, when applying floor coverings over concrete substrates, some floor coverings require light grinding or shot blasting to a specific concrete surface profile, while others require more aggressive mechanical surface preparation. to obtain a tenacious adhesion. Slab moisture conditions such as RH, MVER and alkalinity (pH) level should also be considered by installers.

In addition to ASTM F1869-16a and F2170-19a, ASTM F710-19e1 supports the acceptability of preparing a concrete subfloor for the installation of a finished resilient flooring product, ensuring the resolution of substrate profiling issues and the resolution of potential bond failures. This ensures that the conditions are acceptable for installing the resilient flooring in a timely manner.

Despite the widespread adoption of these test methods, there remains an alarming amount of flooring failures. From hospitals to office buildings, hotels to college campuses, rushed construction, tight budgets, and a lack of awareness of these testing standards have resulted in $2.4 billion spent each year in the United States to remove dampness. and repair or replace damaged floors, based on data from Independent soil testing and inspections.

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