Moisture Testing: A Critical Step in Flooring Construction

When concrete hardens, it is hard to imagine that it began as a liquid slurry composed of aggregate, cement, and water. Because water is a primary ingredient in concrete, moisture slowly dissipates over the years. While the impact of moisture on concrete hardly matters for outdoor surfaces, it is a significant consideration for indoor applications. If you are using concrete to build residential walls and floors, moisture will affect its performance and quality.

How does moisture impact flooring?

Moisture is an issue with concrete, especially when it is not allowed to dry correctly. Moisture testing is necessary because the highly porous surface of concrete allows moisture to seep into the surface. If you install flooring on concrete with high moisture content, the flooring will trap the water vapour inside. If moisture cannot evaporate, it will encourage mould and mildew growth. Humidity also contributes to flooring damage, especially for organic materials like wood. As a result, flooring will warp and bubble.

Testing concrete moisture level

One critical step in constructing flooring is checking for moisture. Contractors use either a relative humidity meter or a calcium chloride kit. These methods are precise and provide definitive results. The moisture level of concrete becomes the deciding factor in choosing the appropriate flooring material. Most flooring manufacturers indicate the suitable moisture level the product can tolerate.

DIY moisture testing

If you do not have the tools used by professionals, you can test for moisture using duct tape and clear plastic sheets. Cut pieces of plastic and tape them over the areas of concrete you want to test. After 48 hours, check if the plastic is wet. However, this simple test is not sufficient to determine what type of flooring material you will use. In determining the moisture rate of concrete, you still need to use a testing device.

Flooring materials and concrete moisture content

The amount of moisture in concrete becomes increasingly problematic in basements. The higher humidity levels worsen the condition of the floor. Similarly, the same problem ensues in new concrete floors that did not undergo proper curing and drying. One way to reduce the impact of moisture on flooring is to add a subfloor so that flooring does not come in direct contact with concrete. In general, the following types of floors are most compatible with concrete:

  • Porcelain or ceramic tile flooring
  • Moisture resilient flooring such as luxury vinyl
  • Rubber tiles
  • Natural stone flooring like marble

If the concrete has high moisture content, you need to avoid using the following flooring materials:

  • Carpet
  • Solid wood
  • Engineered wood
  • Laminate

Nevertheless, many flooring manufacturers advertise products as resistant to moisture. Even laminate and wood flooring can be installed on top of concrete without encountering any issues. It is best to follow the manufacturer’s installation guidelines to know the most appropriate way to use the flooring material.

For most above-ground flooring installations where the concrete was allowed to dry correctly, choosing flooring material is not an issue. This is typically the case with multi-level buildings where there is ample time to allow complete moisture evaporation from concrete.

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