2 METHODS REQUIRED FOR
A successful flooring installation begins following the completion of using both the calcium chloride and in-situ (RH or relative humidity) tests.
These two testing methods are recommended to acquire accurate results. Proper floor preparation is an essential requirement prior to the installation of moisture sensitive floor covering products on concrete. Floor prep begins with the accurate testing for both the moisture content of the concrete and the rate of moisture emissions.
In-situ tests, commonly measured with moisture meters, measure RH of the slab to assess the moisture content in the concrete that can potentially be emitted at the surface. Calcium chloride tests, on the other hand, measure the moisture vapor being transmitted.
The importance of conducting both tests is simple: While an in-situ test may provide an acceptable reading of relative humidity, there may be excessive emissions actually emanating from the surface. In contrast, there may be virtually no emissions but the slab may in fact contain a large amount of moisture that would be emitted once the vapor pressure conditions above the slab change. Check with the manufacturer of the moisture sensitive product you are using to determine if both test methods are required. If in doubt, the safest answer is to perform both tests.
The Taylor Tools #625 Calcium Chloride Moisture Test Kit accurately measures the amount of moisture (in lbs.) coming through the slab over a 1000 sq. ft. area during a 24hr. period. The kit is inexpensive and includes independent test results as part of the kit cost. The kit includes a pre-weighed plastic dish with an airtight snap lid containing anhydrous calcium chloride. It also includes a transparent plastic cover with pre-applied adhesive to secure the plastic cover to the floor in an airtight fashion.
When measuring relative humidity with a moisture meter, be advised that ASTM 2170 guidelines stipulate that RH readings to be taken at 40% of the thickness of the concrete slab. The traditional way of making that determination involves drilling a hole through the slab, inserting a bent wire to catch on the underside of the slab then measuring the length of the wire. After completing the measurement, the hole needs to be patched. It is critical to test in multiple areas of the jobsite as the slab thickness may be inconsistent across the concrete surface.