Laminate on concrete slab

[CC Solutions]

HVAC will make a difference. Think of your concrete as a big sponge. If the air is humid the concrete may absorb moisture, if the air is very dry the concrete can emit moisture.

Another consideration is the concrete on grade is typically cooler than the airspace around it because it is in contact with the cool ground. A slab at 65 degrees may collect condensation if the temperature and humidity in the air around it gets to about 75 degrees and 70% RH.

The plastic sheet test will show you if the slab is actively emitting a large amount of moisture during the time you have the plastic in place. Only a relative humidity test will show you if there is a large amount of moisture in the concrete just waiting to cause you problems. It's for this very reason that most flooring manufacturers are rejecting the antiquated calcium chloride test for moisture emission and are embracing the relative humidity test.