Relative humidity (RH) testing (ASTM F-2170-16) is conducted through the direct insertion of in-situ probes that measure RH deep within the slab. Their depth-specific application has proven to provide an accurate representation of moisture conditions within the concrete slab.
RH measurements taken "in" the concrete are less susceptible to environmental influences or ambient changes at the surface of the sub-floor.
According to ASTM standards, the concrete must stabilize at service conditions for a minimum of 48 hours to meet ASTM Standards for conducting valid moisture (relative humidity) testing.
Equilibration or stability occurs when a drilled hole achieves thermal and moisture equilibrium. For the accuracy of the readings it is necessary to wait until equilibrium is restored after drilling.
Moisture’s migration through drying concrete can vary depending on ambient conditions like air humidity, temperature and surface conditions. It is imperative to know the slabs internal moisture condition before installing flooring.
Now, if a slab has been power-troweled, its surface loses the ability to release moisture in the slab at the surface level. Drying time will slow or even stop completely.
Keep in mind that all flooring as all adhesives are not created equal. But generally speaking most floors and adhesives can be installed at RH reading under 80%.
The type of flooring product to be installed determines the acceptable level of relative humidity in the slab itself. Different RH specifications apply to different materials such as resilient flooring, wood, adhesives, sealers and epoxy coatings.
Always check with the floor-covering manufacturer for a relative humidity specification.Most flooring manufacturers, adhesive manufacturers and industry associations recognize and specify relative humidity testing.
ASTM F2170-16 gives general industry guidelines. Typical relative humidity requirements range from 75% to 90% RH, depending on the flooring and or adhesive product be installed.
All flooring and adhesives come with manufacturer installation instruction on the box, on the bucket and in the can. If no instruction are available on the job site, they most likely can be found on-line. It is imperative that you read and follow these installation instruction.
Test methods like calcium chloride kits or hand held surface meters do not get into the slab for a true overall moisture picture that is key to successful flooring installations. But they do prove to very useful during the slab evaluation process.
Understanding the conditions, test method and timing of the moisture conditions in the concrete slab will help you to better insure a successful flooring installation.
Floor Testers, LLC. 2016 - All rights reserved.