Moisture Measurement in Concrete Floor Slabs: A specifier’s primer

What does this mean for construction specifiers?
Measuring moisture only at the concrete surface does not account for changing ambient conditions, for the moisture gradations throughout the slab, or for the all-important moisture equilibrium that occurs after floor installation. As discussed in this article, most types of moisture testing are largely inadequate or misleading. Years of scientific testing, along with extensive use in the field, indicate in-situ RH testing is the one proven, accurate way of getting at the real moisture condition of a concrete slab. No other test method has been shown to be as consistently reliable for avoiding unnecessary and costly flooring failures. (The in-situ RH specification is available for download at Those wanting to learn more about moisture measurement in concrete slabs, can access a free online course hosted by Howard Kanare, an expert in the interactions of concrete floors and moisture. Visit

Therefore, it is important specifications for a project always identify the specific concrete moisture test to be conducted. This decision should not be left to someone who may unknowingly choose a moisture test method yielding misleading or inaccurate results.

It is useful to keep in mind the moisture condition of the concrete slab is closely tied to pH—a measure of hydrogen ion concentration. This can be assessed quite simply using a pH meter.

When moisture is not an issue, pH should not be one either. Still, given highly alkaline conditions will typically lead to de-bonding and other serious flooring issues, it is generally good practice to test the pH, and many flooring manufacturers require it. 

Jason Spangler has 17 years of experience in sales and management in a spectrum of industries. He has successfully launched a variety of products to the market, including the original Rapid RH concrete moisture tests. Spangler works with Wagner Meters as its Rapid RH product sales manager. He can be reached at

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