The Bottom Line of RH Testing

Relative humidity (RH) testing is a 21st-century challenge to the traditional anhydrous calcium chloride test. Over the years, contractors have deployed various means of measuring concrete moisture content (MC). Calcium chloride testing dates back to the 1940s, and since that time, flooring contractors have shaken their heads as concrete moisture problems ensued. The anhydrous calcium chloride test said they could proceed, and then moisture proved to be a problem. Repeatedly, the industry came to realize that concrete slab was not given sufficient time to dry.

With decades of performance difficulties, the flooring industry began to question its methods for measuring concrete MC. Experts began to wonder if the moisture vapor emissions rate (MVER) assessed by the anhydrous calcium chloride test was too confined to the slab surface. By the turn of this century, the anhydrous calcium chloride test had come into question.

Concrete Facts

RH represents a fresh methodological approach to concrete MC measurement. Wagner Meters developed its Rapid RH® system to assess RH at 40 percent slab depth with in situ probes installed within the slab through drilled holes. The Rapid RH® features Smart Sensors which equilibrate to produce meaningful MC data within one hour of installation. This being said the ASTM standard does require a 72-hour reading prior to making an installation decision. Wagner Meters’ Smart Sensors remain in the concrete slab in order to provide ongoing, instant sensor-to-sensor RH readings, should this be necessary. The Rapid RH® helps contractors to make immediate and informed decisions on slab moisture management.


In times of intense productivity, The Rapid RH® provides crucial cost savings for builders. If time is money, the Rapid RH® is a recipe for meeting installation budget targets. Compared to the anhydrous calcium chloride test, the Rapid RH® in-situ test method saves over 150 hours of installation time (based on industry estimates for tests on 13 slabs). The Rapid RH® rewards thorough slab installers with multiplied cost-savings.

Rapid RH® Time (Cost) Savings:

  • Preparation: 130 minutes
  • Site protection: 120 minutes
  • Test processing: 125 minutes
  • Clean-up: 13 minutes

The Rapid RH® test accurately identifies how much excess moisture remains inside the slab. As those results inform professional decisions, contractors allow sufficient drying time or make alternate choices for flooring and adhesive installations better suited to the current RH level within the slab.

Put simply, the Rapid RH® system makes business sense.


In the early 2000s, the American Society for Testing and Materials (ASTM) established standard F2170 protocol, which outlines the proper procedure for in-situ RH concrete assessment. In fact, ASTM F2170 has become the standard for lightweight concrete slab installation. Since then, the standard for RH testing has been updated several times, and Wagner’s Rapid RH® consistently keeps step with the ASTM F2170 updates and ensures full compliance with this industry standard.

Although the American Society for Testing and Materials has disallowed ASTM F1869 for lightweight concrete applications, the standard still applies to other types of slab moisture assessment as measured by the anhydrous calcium chloride test. The MVER satisfies F1869 at the time of concrete assessment.

The Rapid RH® for ASTM F2170 and the anhydrous calcium chloride test for ASTM F1869; which one to choose?


Concrete slabs perpetually hold a certain amount of MC, so contractors need to assure that concrete has sufficient time to reach the in-situ RH level specified for the intended flooring application. If RH is too high, the risk of adhesive or flooring failure rises accordingly.

The Rapid RH® contains several crucial features to assist flooring installers with RH measurement. With accurate RH testing, contractors ensure accurate levels of moisture internally in order to make the most informed decisions. With this information, installers can make informed, accurate decisions on when they can safely apply adhesives and floor coverings that will last for the duration. The Rapid RH® provides state-of-the-art concrete moisture measurement, so contractors can have the most accurate information to make well-informed decisions, therefore ensuring a completely successful flooring installation.

History brings change, and RH testing facilitates a fundamental shift in concrete moisture management methodology. The Rapid RH® allows builders to save, certify and succeed in concrete slab installation.

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Jason Spangler

Jason has 20+ years' experience in sales and sales management in a spectrum of industries and has successfully launched a variety of products to the market, including the original Rapid RH® concrete moisture tests. He currently works with Wagner Meters as our Rapid RH® product sales manager.

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