The Importance of Accurate RH Measurements in Concrete

Posted by Tom Laurenzi on Jan 3, 2015 12:58:00 AM

Before building on top of concrete, it is necessary to make sure that the concrete is properly cured first.For any flooring contractor, following the ASTM-F-2170 standard for concrete is important. By adhering to this standard for construction on concrete, you can protect your work, and thus your reputation as a contractor.

The most integral part of following ASTM-F-2170 is being able to take accurate readings of the relative humidity (RH) conditions inside the slab. Without knowing the RH conditions of a slab, it is impossible to know the condition of the slab for flooring installation, adhesive or other coating.  

Adhering to ASTM-F-2170 with Accurate RH Readings

Under the ASTM-F-2170 testing standard, flooring contractors need to test the RH of the slab itself. This is done using a thermo-hygrometer with in-situ probes.

The basics of the ASTM test involved drilling a hole in the slab, inserting a sleeve into the hole and then capping the hole to allow the cavity to acclimate.  After acclimation, the RH sensor is inserted and a reading can be taken. Such readings are repeated until the concrete is ready at proper levels.  

To ensure maximum accuracy, and adhere to the ASTM standard, the calibration of the sensor must be checked once every 30 days. If a sensor is not checked at least that often, then the standard will not have been adhered to, and the sensor’s readings might be considered invalid for testing purposes.

Why Stick to ASTM-F-2170?

There are several reasons to utilize this standard when installing flooring or doing other construction work.

First, and foremost, the F-2170 standard is a reliable method for ensuring that concrete is sufficiently dry to build upon. Many flooring, adhesive, and coating manufacturers name this standard as an approved testing method for the use of their particular product. Adhering to this test method, contractors can accurately predict how a concrete slab will behave later on.

Another reason to use ASTM-F-2170 standards for testing concrete is that failure to do so can void warranties for flooring installation products. Remember how many manufacturers cite F-2170 as an accepted testing method? If concrete isn’t tested via an approved method before installing other flooring, then the manufacturer will not be held responsible for damage that occurs as a result of moisture bleeding from the slab.

Finally, using the ASTM-F-2170 standard helps to protect your reputation as a reliable flooring contractor. By getting the job done right the first time, you can avoid callbacks that cost you time and money, and insure having a happy customer.  

Consequences of Bad RH Readings in Concrete

As was mentioned before, adhering to the ASTM standard requires the use of an accurate testing method, such as an RH meter with an in-situ probe. If the readings provided by the RH meter are not accurate, it can lead to a false conclusion about the RH conditions deep in the slab.

At the least, an inaccurate reading could cause delays in construction, as the concrete is incorrectly assessed as being too wet to build on. However, building on concrete that is still wet when you think it’s dry can be much, much worse than a simple delay.

What can happen if concrete is too wet when other flooring is installed? Consequences include:

  • Excess moisture in a concrete subfloor can ruin wood flooring that is installed over said concrete.Cupping, warping, and buckling. Wood will absorb excess moisture as it bleeds from a concrete subfloor. As the wood absorbs moisture, it will expand, causing a number of deformities when adjacent pieces of wood push against one another.

  • Adhesive failure. The adhesive used to secure top floor materials to the subfloor can fail, causing tiles or wood to become loose.

  • Mold. Mold can grow in almost any damp, dark environment where there is carbon to feed on, such as the underside of a wet piece of wood.

In any of these situations, there will be an immediate need to come back and redo the job. The old flooring will need to be ripped up, and new flooring installed to take its place. This costs you time and money.

Not only does redoing an expensive flooring job cost you money for the materials needed to do the job, it costs you by making you unavailable for other jobs, which creates an opportunity for a competitor to step in and pick up a contract that should have been yours.

Once damaged, a good reputation is very difficult to restore. Keep yours intact by using a reliable thermo-hygrometer for your RH testing needs, and taking care of said meter so that it remains accurate for a long time to come.

Learn more about how you can ensure accurate readings from your RH-sensing thermo-hygrometer today by checking out our Relative Humidity Sensor Behavior and Care guide or by contacting Delmhorst directly.

Topics: Wood Flooring Flooring concrete