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Home » Concrete Moisture: How to Find It & How to Fix It

Concrete Moisture: How to Find It & How to Fix It

Moisture is the enemy of strong floors.

Proper concrete preparation, as we’ve covered before, is the foundation of every strong floor. All too often, contractors forget one incredibly essential aspect of preparation: concrete moisture. Moisture can significantly impact the success of epoxy coatings.

In this blog post, we delve into the crucial importance of moisture mitigation in surface preparation. We’ll talk about why it matters for epoxy flooring, and how contractors can fix it!

The Hidden Threat: Concrete Moisture

Concrete may seem solid and impermeable, but it can contain hidden moisture that can wreak havoc on epoxy flooring. Some describe concrete as a sponge, especially when it comes to water & ambient humidity. Here at Epoxy Classes, we know from experience that all of this jeopardizes epoxy coatings.

DeFelsko highlights how excess moisture, “can accumulate below the coating or flooring causing discoloration, cupping, buckling, blistering, adhesive failure, and/or mold growth.” This hidden threat doesn’t always show on the surface, either. It can hide in the concrete until temperatures rise, or fall, or just by the passage of time. This makes testing incredibly important.

Uncovering the Causes

Understanding the sources of moisture in concrete is vital for effective mitigation. As ConcreteMoisture puts it, “you’re never going to achieve, nor would you want, 100 percent dry concrete.” But you still need to account for any excess moisture! Common culprits include a few factors, some from installation, some from age. As a contractor, you should always know your floor before you start work on it.

One of the most common sources of moisture is just the freshness of the concrete. Freshly poured concrete releases moisture as it cures. This moisture must evaporate before coatings can be applied. Another common source is from hydrostatic pressure. Moisture can rise from the ground through the concrete due to hydrostatic pressure, especially in areas with high water tables.

Lastly, the older your concrete foundation is, the more likely it is that it’s picked up moisture from humidity. Especially in more temperate climates, like Florida’s infamously humid summers. Atmospheric humidity can seep into the concrete over time, causing surface moisture issues.

The Importance of Concrete Moisture Testing

Epoxy Classes’ professors understand the need for thorough moisture testing as a foundational step in the preparation process. That’s why we teach every step of installation, including testing. Moisture testing is a diagnostic tool to determine the moisture content within the concrete substrate.

This is crucial because even seemingly dry concrete can harbor moisture, and applying coatings without accurate testing often leads to adhesion failure. A good moisture meter from EpoxyETC is a concrete contractor’s best friend!

Flooring contractors working on an epoxy floor applying moisture barriers & epoxy resin.

Effective Methods of Concrete Moisture Testing:

Moisture Meters:

Moisture meters, also known as moisture content testers, are handheld devices that measure the moisture content within the concrete. These meters use different technologies, such as pin-type or non-invasive capacitance-based methods, to provide accurate readings.

For pin-type meters, insert the pins into the concrete at various locations and depths. Be thorough! For non-invasive meters, place the device on the concrete surface and follow the manufacturer’s instructions. As you can imagine, invasive meters provide more accurate results, but any testing is better than no testing.

Relative Humidity Testing:

Relative humidity testing involves placing sensors within the concrete to measure the relative humidity. This data helps assess whether the concrete is suitable for coating application. This is especially important if you live in a humid climate!

To do relative humidity testing, you’ll need to drill holes in the concrete and insert the relative humidity sensors. Seal the holes and leave the sensors for the manufactured specified duration, usually 24-72 hours.

Calcium Chloride Testing:

This method involves placing a sealed calcium chloride container on the concrete surface. The container absorbs moisture, and the weight gain is measured to determine the moisture vapor emission rate (MVER). Follow the manufacturer’s guidelines for placing the container on the concrete surface. Seal the container and leave it for the specified time, typically 60-72 hours.

ConcreteDecor talks about a few of these methods in-depth, but these are the most widely used methods.

Effective Ways to Solve Concrete Moisture

If you want a strong floor for your clients, you have to add effective moisture mitigation strategies to your toolkit. Here are some key methods:

  1. Moisture Barriers: Moisture barrier/vapor reducing products like EpoxyETC’s high quality line are specifically designed to counter hidden moisture. They act as protective shields, preventing moisture from migrating to the surface. EpoxyETC offers a range of moisture barrier solutions designed to create a reliable moisture barrier between the concrete and the coating.
  2. Surface Preparation: Proper surface preparation involves shot blasting or diamond grinding to create a porous profile that promotes strong adhesion while allowing moisture to escape. If the moisture levels aren’t too high, you can skip the moisture barrier and move straight to your mechanical preparation.
  3. Epoxy Primer: A high quality epoxy primer should inherently create a barrier that inhibits moisture penetration while enhancing coating adhesion. That being said, if the moisture content is too high, you’ll still need to apply a moisture barrier first.

The Role of Epoxy Classes

Epoxy Classes is committed to equipping flooring contractors with the knowledge and skills needed to address moisture challenges effectively. Our comprehensive 5-day epoxy resin and concrete polishing certification course covers moisture testing techniques, mitigation strategies, and hands-on training in surface preparation!

With hands-on training and experienced professionals by their side, contractors can confidently tackle moisture-related issues and build more successful epoxy floors. Get a head start on the competition today!


Moisture in concrete might be invisible, but its effects on epoxy flooring are far from hidden. Understanding the sources of moisture, conducting thorough testing, and implementing effective mitigation strategies are essential steps to ensure the longevity and quality of epoxy coatings. As Epoxy Classes empowers contractors with the tools to master these techniques, the threat of moisture should be a manageable challenge. Choose knowledge, choose preparedness, and choose Epoxy Classes to help you create epoxy flooring that stands the test of time.

At EpoxyClasses, we aim to equip contractors with the industry knowledge they’ll need to succeed. Whether it’s through our class or through our support, we’re here to help. Our technicians are a phone call away at (954) 287-3797! To resupply your toolkit, the EpoxyETC online store will deliver high-quality resources at affordable rates!