Concrete Moisture Content For Flooring

Understanding relative humidity in concrete.

Concrete moisture content for flooring.

A definitive test that measures the amount of moisture released from the concrete requires a calcium chloride kit or a relative humidity meter. Concrete slabs and floors can be excellent subfloor surfaces for tile and other floor coverings but too much moisture in the concrete can cause problems with flooring installations. In this section we breakdown the main ways water can get into your concrete which causes a buildup of excess moisture and list effective methods to prevent moisture problems from occurring. Mfma does not recommend testing for concrete moisture content within 60 days of pour.

Testing with either method will tell you how precisely how much moisture is present making it possible to choose a surface flooring that is appropriate. Commonly concrete floors are vulnerable to moisture and suffer from different detrimental influence of moisture such as lifting tile off the floor rotting hardwood damping carpet coating delamination and many more. Concrete slab moisture content installation of an mfma flooring system shall not commence until the subfloor is determined to be dry by industry standard testing procedures. The answer may depend on your next step.

How moisture gets into concrete. If your concrete contains excess moisture and high rh levels this can lead to disastrous flooring failures resulting in costly repairs and liabilities. Before installation the moisture content of the subfloor should be within 4 percentage points of the new flooring fig. So there isn t a truly accurate way to objectively establish the precise moisture content mc of concrete.

This can also affect what a safe level of moisture in the slab would be as denser mixes might be less prone to letting moisture escape all at once. Therefore it s advisable to have a floor tested for moisture content prior to installing flooring or moisture barriers. It is vitally important to test your concrete slab s moisture before installing flooring over it. These problems are not only disrupting functions of the building due to maintenance operations but also costly.

Three methods for testing concrete moisture levels. Duct tape an 18 inch square piece of plastic onto the exposed concrete and leave it for 16 hours. Acceptable moisture levels in concrete according to astm standard when testing via astm f2170 the rh level of a concrete slab needs to be at or below 75 unless the flooring system manufacturer provides alternate guidelines. One of the simplest most economical test methods for determining whether there may be moisture in concrete is the astm d 4263 concrete moisture test.

If the moisture content between the new flooring and subflooring varies more than 4 percentage points or 2 for boards wider than 2 1 2 the flooring should not be installed. Condensed moisture accumulation under the plastic at 16 hours can indicate a problem. During the construction of a concrete building an essential step in the application of flooring is the importance of monitoring the relative humidity rh moisture levels and the moisture evaporation rate of your slab.