Concrete floors: mitigating steam related faults

Photos provided by Maxxon

Written by Heather (Yario) Rice

Whether it is new construction or renovation, proper floor preparation is essential to carrying out a quality floor installation while extending the life of the finished floors. In the past twenty to thirty years, regulations for volatile organic compounds (VOCs) have made buildings safer for their occupants; However, these regulations have also created new challenges for designers and general contractors, such as in cases of flooring failures associated with moisture vapor.

As the industry’s understanding of moisture emissions has grown, so have the types of solutions to mitigate the problem. Today, a new class of moisture barriers makes it easier and more cost-effective than ever to properly prepare concrete for finished pavers.

On July 2, 2003, ozone and its precursors, including VOCs, were added to Table 1 of Canadian Environmental Protection Act, 1999 (CEPA 1999). This has provided Environment Canada with additional tools and legal authority to develop and propose measures to control VOC emissions. Since then, Environment Canada has continued to review and update its VOC regulations. On May 2, 2015, an order proposed to amend the definition of VOCs as listed in Table 1 of CEPA 1999 Posted in Canada Gazette, Part One. Removing solvents from adhesives makes them compatible with VOCs; However, the resulting products were sensitive to moisture vapor in a way the industry had not seen before.

Anhydrous calcium chloride (CaCl) test for ASTM F1869, to measure the moisture vapor emission rate (MVER) of concrete floor.

In the author’s notes, prior to the adoption of VOC regulations, moisture-related failures were largely unheard of. They note that flooring faults began to occur more frequently in the early 2000s. The flooring industry quickly learned that moisture vapor emissions were to blame. Not only were these types of emissions common, but they can also come from a variety of sources. Panels, especially on grade, can vary in moisture content and emission levels. From groundwater intrusion to major weather events, the amount of moisture present throughout a slab can vary, increasing and decreasing seasonally and throughout the life of a building. Panels that have been tested with low moisture emissions for weeks, months, or years can still fail down the road.

Common building practices also have the potential to cause moisture-related problems. A hard slate burning or grouting process was used to achieve floor flatness but had the secondary effect of sealing the surface. The application of curing and sealing speeds up the curing process and seals the surface to protect it from commercial damage. When it is time to install the flooring, manufacturers will require that the surface of the slab be opened to remove the joints.

Since both processes trap moisture in the slab, opening the surface allowed water vapor to escape as the slab’s relative humidity (RH) sought to balance with ambient conditions on the job site. Not only did this cause condensation to form when the adhesive bonded to the board, but it could also pull the alkaline from inside the board to the surface, creating a high pH environment. Standard adhesives can handle a pH of nine, while a freshly opened tablet can easily reach pH 11 in a short time frame.

Under the floor, one of two things will happen: Either the adhesive will not dry or the adhesive that was dry when the floor was installed will emulsify. This is where mold, mildew, and other severe floor failures will start. As with any emerging issue, preliminary tests and solutions must be developed before improvement is possible.

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