‘Moisture’ is a simple word that can lead to anguish for flooring professionals and building owners. More specifically, ‘excessive moisture vapor emission’ can cause the failure of both soft and hard flooring installations. But it is preventable. Understanding when, why and how to mitigate will help prevent moisture from marring your installations.
Moisture enters flooring installations through vapor transmission, which sometimes begins long before installation starts. In fact, moisture often enters the subfloor when it is first poured. This water may eventually migrate from within the slab to evaporate at its surface.
As an installer, it’s your job to look for potential moisture problems – even if they begin long before you arrive at the job site. After all, if left unaddressed, moisture can move through the slab and break down flooring adhesives, which warps and buckles the flooring. Moisture can also lead to microbial growth in the flooring system, as well as deterioration of the finish flooring and coatings.
Selecting the very best moisture solution means taking several factors into consideration – especially the relative humidity and condition of the slab and the job’s specific requirements and timeline. First, test your substrate’s moisture levels, using the ASTM F-2170 test. Because moisture migrates upward from within the slab, measuring moisture at its surface will not accurately portray the subfloor’s relative humidity. Probes placed at specified depths inside the slab more exactly measure its relative humidity levels, and as a result, more reliably measure the risk moisture poses to a particular installation. Be sure to follow the instructions of your relative humidity equipment, and refer to the flooring manufacturer’s guidelines for the recommended relative humidity levels and testing procedures.
Note that moisture test results indicate the moisture condition of the slab only at the time of the test. Although concrete absorbs water from the ground, it can also absorb water vapor from the air in humid conditions. Moreover, concrete releases more water vapor when the air humidity is low. These fluctuations in environmental conditions can affect relative humidity levels.
Some admixtures can prevent concrete from emitting moisture vapor. However, once the concrete slab is in place, topical application of a moisture vapor barrier is the only option for moisture mitigation. These liquid coatings are applied to the slab, where they will prevent moisture from seeping up and into the flooring system. When selecting your topical product, keep in mind the new ASTM F3010-13 standard for moisture vapor barriers. This standard explicates the properties, application and performance of moisture mitigation systems on high-moisture concrete floors before installing resilient flooring. Look for products that meet or exceed this standard.
Keep your job’s timeline in mind when selecting a moisture mitigation system. Some products can be applied to damp or new concrete as little as 48 hours after concrete placement. And some moisture vapor barriers require no shot-blasting, need only one coat and cure within 4 to 5 hours, allowing for same-day flooring installation. When time is an issue, look for these products.
Once you’ve determined that mitigation is necessary and selected the right product for the job, ensure that your surface is strong enough for a proper bond with the moisture vapor barrier. Test the substrate with a knife. If it produces a fine powder, mechanically prepare the surface by grinding or shot blasting. Then clean the surface until it is free of debris. If your surface does not produce any powder, your floor should be contaminant free. Consult with your mitigation system’s instructions for more specific surface preparation requirements, as well and mixing and application instructions.
Both efficiency and frugality are valued during floor installations. Although moisture testing and careful product selection require an initial expenditure of time and money, they can ultimately save you and your client from frustrating and costly callbacks.