We've been asked the question, Do we need to use other types of moisture testing for floors besides relative humidity? Is it a good idea to use multiple methods to understand the moisture condition of the floor?
In our opinion, relative humidity is the only method that's necessary because it reveals the true moisture condition within the concrete, which is what the floor covering will see after it's installed. Other methods, such as the calcium chloride moisture emission test, we've shown to be misleading, and therefore, the most reliable test is really sufficient by itself.
The electronic handheld meters, as we've seen, only indicate a small portion of the moisture near the surface of the concrete, and, again, don't give us a true picture of what's happening deeper down.
When we put in situ probes into the concrete slab, we see the true moisture condition and it's the best predictor of long term performance of the floor.