Proper floor preparation is an essential requirement prior to the installation of moisture sensitive floor covering products on concrete. At the top of the floor prep list is accurate testing for both the moisture content of the concrete and the rate of moisture emissions. That’s right . . . two separate tests.

In-Situ tests measure the relative humidity of the slab to assess the moisture contained in the concrete that can potentially be emitted at the surface. Calcium Chloride tests, on the other hand, measure the moisture vapor actually being emitted.

The importance of conducting both tests is simple: While an in-situ test may provide an acceptable reading of relative humidity at 40% of the slab depth, there may be excessive emissions actually emanating from the surface. In contrast, there may be virtually no emissions while the slab may in fact contain a large amount of moisture that would be emitted once the vapor pressure conditions above the slab change.

Either case could create major installation problems. And in light of recent tests conducted on the in-situ probe method (relative humidity) at W.R. Grace under the auspices of the ASTM committee, it is even more important to conduct both tests. The in-situ test showed a discrepancy in relative humidity readings from one manufacturer to another. The ASTM effort is now to standardize probe and sleeve design to reduce these variations.

Installers and technicians who currently combine both the in-situ and calcium chloride tests will benefit from these proposed refinements to give both the installer and the customer a reduced risk of floor failure.

Through our worldwide distributor network, Taylor Tools provides both types of moisture testing products - Calcium Chloride test kits and In-Situ Moisture Meters.

Both the moisture content of concrete and the amount of moisture being emitted
are independent variables and subject to change depending on atmospheric conditions.
Therefore, both moisture testing procedures are required for accurate evaluation.