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Before floor covering is installed, concrete dryness testing (ie. concrete moisture testing) and pH testing must be performed to meet ASTM standards. This testing is conducted to prevent potential flooring failures, which costs commercial property owners millions of dollars per year to remediate.

First, let’s talk about the two methods used to measure concrete dryness:

  1. In-Situ Relative Humidity Testing is done by drilling holes about 40% deep into the concrete slab and then setting probes for 2 days and readings are taken on day 3. These probes measure the percent of relative humidity within the slab that will likely come to the surface once floor covering is introduced.
  2. Calcium Chloride Testing involves sealing a small dish of calcium chloride on a clean section of concrete under a plastic dome. The salt absorbs moisture in that environment and the weight gain after 3 days is used to calculate the moisture vapor emission rate (MVER) of the concrete slab measured in pounds.

The biggest difference between these two tests is that In-Situ measures the moisture within the slab, whereas Calcium Chloride measure the moisture being emitted from the slab. We prefer In-Situ Testing because it provides more predictive data that is less impacted by the introduction of floor covering. Whereas, Calcium Chloride Testing only tests the top 1/4″ – 1/2″ of the slab, which doesn’t account for the entirety of the slab. When floor covering is installed, a greater volume of moisture may travel up through the slab than what was originally anticipated.

In addition to testing concrete dryness, pH surface testing is also required. pH testing measures the acidity/alkalinity of the surface of the concrete. There are two methods commonly used:

  1. Electrochemical Method using electrodes and a millivoltmeter (Electronic Digital pH Meter)
  2. Colorimetric Method using distilled or de-ionized water and pH test strips (pH paper)

We prefer the pH meter testing method because it’s more precise and leaves less room for human error as people may perceive color differently.

When is testing imperative?

  • Anytime you’re dealing with slab-on-grade regardless of whether the slab is new or existing.  Unlike an elevated slab, a slab-on-grade rests directly on the earth below it.  Depending on how old the slab is, it may or may not have an intact vapor barrier underneath to prevent moisture intrusion.  However, if there is no vapor barrier installed or if it’s no longer working properly, then you risk moisture traveling up through the slab. This could happen during wet rainy months or could result from sloped landscaping and/or poor irrigation. All these factors can potentially “feed” the slab with moisture.
  • When you’re installing non-permeable materials. Non-permeable materials do not “breathe”, which means high levels of moisture can get trapped underneath the material causing flooring or adhesive failures, or even mold growth.
  • When the manufacturer requires moisture testing to be conducted in accordance to the ASTM F-2170 (In-Situ) or ASTM F-1869 (Calcium Chloride) as well as the ASTM F-710, which measures the pH/alkalinity of the slab. The manufacturer will not warrant their materials if they’re installed on slabs that exceed their specified moisture and/or pH parameters (this goes for elevated slabs too). If testing finds high moisture and/or pH levels, then those issues must be addressed and mitigated before install can begin.

Make sure you protect your flooring investment by checking off these boxes before your next install.  Feel free to reach out to us if we can help!