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Concrete Moisture Testing Guide (2022)

Concrete moisture testing leads to stronger epoxy.

Before starting any work on your concrete, it’s important to understand the moisture levels within it. Skipping this important step can lead to a weakened finished installation. This guide will teach you how to perform concrete moisture testing so you can guarantee a stronger floor.

As any epoxy flooring contractor will know, surface preparation is one of the most crucial, often skipped, steps of installing epoxy. Cutting corners during preparation leads to repair costs in the long term. If you’re installing epoxy on concrete, moisture testing should be considered an essential part of your surface preparation.

Why You Need to Test Concrete for Moisture

When you install epoxy flooring over concrete, the epoxy bonds directly to the concrete. High moisture levels in concrete could cause the epoxy to bond incorrectly, and it could peel or flake off. In some cases, high moisture levels can even cause the concrete to crumble.

To ensure a strong, lasting installation, it’s crucial to test the moisture levels in your concrete before beginning work. This should involve, no matter your method, testing multiple spots and also the ambient moisture of the space. Epoxy is a strong system that lasts for years after it cures, but it’s up to you to ensure that it has the proper foundations.

How-to: Concrete Moisture Testing

An image showing concrete contractors assessing an industrial concrete floor.

There are a few different ways to test the moisture levels in concrete. From destructive methods requiring inserting a probe into the concrete, to more non-destructive meter based tests.

Moisture testing procedures vary in size, thoroughness, accuracy, invasiveness and more. You can find the right one for you depending on your on site needs with the help of this guide. The ASTM industry standards for moisture will be your manual to interpreting the testing results.

Whichever method you choose, it’s important to test more than one spot in the concrete. It’s also essential to take into account the ambient temperature and humidity levels.

Plastic Sheet Test

One of the more vague testing tools is the plastic sheet test. The Plastic Sheet method saves you money upfront, but it is not accurate enough to truly understand the moisture level. This most likely will lead to your epoxy system failing due to moisture exposure down the road.

Calcium Chloride Testing

If you don’t have a moisture meter, you can also test the moisture levels in concrete by using a calcium chloride test kit. This involves mixing a specialized powder with water and then applying it to the concrete. The powder changes color if the concrete is too wet.

Calcium Chloride is slightly more accurate, and is a preliminary procedure to determine if you’ll need a more invasive test. Be aware, though, because the testing kit really only performs a surface level analysis of the concrete.

Non-Invasive Meter Testing

Meter testing is the most convenient and efficient testing procedure for surface (and slightly into) moisture in concrete. A meter analyzes the concrete’s moisture level by transmitting electrodes into a slab, and feeds results based on the signal. This test does not require you to damage your concrete, but as a result it is not the most exhaustive test of the deeper moisture.

Of the surface analysis methods of concrete moisture testing, this is by far the most accurate. For most on site needs, you can feel comfortable installing epoxy with just meter testing.

For your meter testing needs, we sell a top of the line non-invasive device on our EpoxyETC website, the Tramex CME5 Concrete Moisture Meter.

In-Situ Probe Testing

If you want to be exhaustive before applying epoxy, and you don’t mind slightly damaging the concrete base, you’re rewarded with accuracy by probe testing. By probing about 40% of the slab’s depth, you can test for deeper moisture that could ruin your epoxy installation in the long term.

Destructive testing, like probing, offers more than the alternatives in terms of fully understanding the moisture atmosphere of your concrete. It does require that you probe into, thus damaging, your concrete. It’s up to you to weigh the risks and the rewards of performing this exhaustive concrete moisture testing procedure.

Learn How to Work With Epoxy

Understanding your surface preparation is an integral part of installing stronger epoxy. Although you can use online guides like this to gain some understanding of the process, working hands-on is the best way to really learn. With our 5 day Epoxy Classes program, you can work with experienced and licensed professionals the ins and outs of working with epoxy, from start to finish. In the class, we cover:

  1. Concrete Moisture Testing & surface preparation
  2. How to install epoxy floors
  3. How to manage & market your epoxy flooring business.

Sign up today and help us kick start your career in the flooring industry!


Once you have your moisture readings, you can use them to decide how best to proceed with your flooring installation. If the moisture levels are too high, you may need to take additional steps to ensure a successful installation, such as adding a moisture barrier. By following the steps in this guide, you can be sure that your installation goes smoothly and lasts for years to come.

If you have any installation concerns, questions about surface preparation, or anything else, call and ask our trusted specialists at (954) 287-3797. From your moisture testing devices to your epoxy resources, you can find it at competitive prices on our EpoxyETC online store.

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