To determine whether too much moisture is present or migrating through concrete, ASTM D4263 “Standard Test Method for Indicating Moisture in Concrete by the Plastic Sheet Method” is useful. An 18" x 18" transparent polyethylene plastic sheet (minimum 4.0 mils thick) is placed on bare concrete and the edges are taped to form an airtight seal. The sheet is left in place for a 16-hour period (minimum). The shortcomings of this method are that the test takes 16 hours to perform and does not quantify the amount of moisture present. Also, floors to be coated are often indoors and no sunlight is present. In this case, place a light (100 watt) approximately 8"-12" over the plastic sheet. However, it can be stated that if any amount of water is detected, during or subsequent to the test, there is probably too much moisture to install a floor coating system.
Usually the frequency of testing can be determined on a per job basis, a minimum of one test per 1,000 sq. ft. of floor area should be performed.
That being said, if you find no moisture you should be good. If you have a gut feeling that you might have a moisture issue, go ahead and perform ASTM F1869 “Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride.
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