How To Test Moisture In Concrete The Right Way

Accurate Results In Concrete Moisture Testing 

One of the worst hazards for concrete is moisture or excess water. Understanding a concrete moisture test can help ensure your flooring installations are top-notch.


Modern concrete can last about 50 years before needing repairs or replacement. Before starting your next project, you should know how to get the most out of your concrete. If you're curious about learning the proper test method, Deslauriers is here to offer our guidance.

Dangers of Moisture in Concrete 

To begin, what are the dangers of moisture in concrete? Concrete is a wet substance before it sets, making it difficult to see why water is bad for concrete. However, moisture levels can prove caustic if your concrete has too much water.


Using too much water can render your concrete floor slabs useless. Will moisture affect your concrete floor cost or cause water damage? Here are some of the most important hazards of moist concrete. 

Humid Rooms 

One issue with moist concrete is that the moisture will seek to escape. If the room with your fresh concrete seems humid, the moisture may be escaping your concrete. The issue will continue until you can sap the moisture out of the concrete. This effect may magnify if your concrete is in a garage or patio.


The heat from being so close to the outdoors can worsen the moisture conditions. These ambient conditions will not only make the room less comfortable but will also damage the concrete. Continued humidity will slowly wear your concrete down over the months. 

Less Secure Concrete 

Concerning damaging the concrete, water is far from good for the flooring material. Some are confused by this, as water is also an ingredient in concrete. Water in concrete can cause it to corrode or fall apart. On the surface, this can lead to an uneven area and chipped concrete. In the interior, the concrete floors can fail to be properly set. 

Cracks Over Time 

One result of less secure concrete is cracks forming over time. The moisture will cause your concrete to swell and expand in areas of significant moisture. As this occurs, your concrete will break away from itself. The resulting cracks can worsen in time and threaten the structural integrity of your concrete. In a storage area or garage, this is particularly dangerous.


The added stress of a heavy vehicle moving over the concrete can worsen cracks significantly. If you use your concrete as the foundation of a building, high moisture can cause it to crumble over time. Ensure your safety by avoiding any cracks or damage to your concrete. 

cracks in concrete cracks in concrete

Longer Time Setting 

One of the first stages of laying concrete is to give it time to "set." "Setting" is the phase where the concrete lies still and hardens. Part of this process is for the concrete to absorb the necessary moisture. 

However, if there's too much water, setting can take significantly longer. For extremely wet concrete, it may fail to ever fully set. Be careful not to get any concrete on you at this time. Wet concrete is hazardous to human skin and should be removed as soon as possible. If concrete dries on your skin, you may need medical attention to remove it. 

Damaging Sealants 

Once the concrete has set, one of the best ways to protect it is by sealing the concrete. Vinyl, polyurethane, and epoxy sealings can help keep moisture out. It will also help with avoiding stains, cracks, and other forms of damage. However, if you seal concrete that hasn't released moisture, you'll seal that water inside. As a result, the water will try to force its way out of the sealant. 

Poor Base Setting

Finally, concrete is often used as a base setting for other flooring installations. Wooden flooring, carpet, and other building materials are often placed on top of concrete. Moisture sweating through can ruin the flooring. 

Even disregarding the damage to the flooring, your concrete's moisture will generate mold and mildew. Mold is linked to a myriad of health issues, especially for people with respiratory difficulties. Mildew can produce an unpleasant, moldy scent while also causing health issues

How to Conduct a Concrete Moisture Test 

Now that we know why having moist concrete is bad, how can you complete a concrete moisture test? There are several ways to measure the moisture. As such, you can pick the humidity test method that best fits you.  For accuracy, many find that moisture meters are the best option. However, a meter with pins often isn't desirable for a polished concrete floor. Here are four ways to test your concrete moisture levels. Doing so will help you measure the amount of water lingering in your concrete. 

Plastic Sheets

The first choice is a DIY option that's low in cost, but not as accurate as you may want. Take some saran wrap or other type of plastic wrap. Cut the plastic sheeting into 24-by-24-inch squares and ensure no holes or tears in the plastic. Holes would let the moisture escape. Place the sheeting flat on the concrete and use masking or painting tape to secure the edges. Leave the sheet for at least 12-24 hours. Afterward, return to remove the tape and check the sheet. 

If the underside is moist, it captures the moisture your concrete releases. While this is a cheap way to test concrete, it doesn't provide enough moisture. This method confirms your concrete has excess moisture before moving on to another method. 

Calcium Chloride Kit 

A calcium chloride test is another accurate way to test how much water comes from your concrete. The kit includes one or two tablets of calcium chloride and a small plastic dome. 
Place the tabs on the concrete in a clear section of the room. Cover the tabs with the plastic dome. The tablets will respond to any water that's released. If they don't react, there's no water. You can judge your floor's moisture content (MC) by how severely the tablet reacted. 

Moisture Meter 

Finally, an accurate moisture meter is the best way to test your concrete. This is one of the ideal standardized test methods when measuring moisture content. Concrete moisture meters involve needing to drill into the floor. 

Drill three probes in your concrete. For every 1,000 square feet, drill an additional probe. Insert your moisture meter's probes and seal them with a cap. After 24 hours, record their readings with a hygrometer. Using this method, you can measure precisely how much moisture is in your concrete. 

You can look into pinless moisture meters instead for testing, resulting in an unclear read. These are often more expensive but don't require drilling into the concrete. 

concrete moisture meter concrete moisture meter

How to Dry Your Concrete 

You must fix the issue once you've confirmed excess moisture in your concrete. If you leave your concrete as it is, you'll need to replace it much quicker. In the meantime, the concrete moisture levels will continue to make the ambient conditions unpleasant. 
Here are the two best ways to dry your concrete. 

Dry the Room 

Your first method is to let the concrete dry out naturally. To do so, leave the room aerated and install dryers in the area. One effective way to dry the room is with low-cost box fans. These are inexpensive, easy to operate, and can keep the airflow moving to whisk away moisture. However, it's not the most effective method. A more effective choice is to purchase or rent an industrial dryer. These will remove moisture from the air and help pull it out of the concrete. 

Redo the Flooring 

You may need to redo the flooring if the concrete was incorrectly prepared. To do so, you'll need to remove the concrete that's there permanently. Removing concrete is a messy, dangerous, and difficult job. We strongly recommend hiring professionals to remove the concrete for you. Additionally, it's best to let professionals handle the concrete laying. While laying concrete is a popular DIY task, letting professionals bring their experience is better. That way, there's less chance that your concrete will be low-quality. 

Here at Deslauriers, we offer custom concrete forms. Our skill in engineering helps us bring your next construction project to life. If you have a customization you'd like for your next concrete project, we're happy to help. 

Handling Your Floor Installations 

Performing a concrete moisture test can help ensure your concrete was correctly mixed. Monitoring the concrete moisture levels can ensure your concrete is safe and stable. 
Allow professionals to handle the most difficult parts so you can enjoy your new installation in peace. Interested in learning more about how Deslauriers can help you perfect your next project? Contact us to see how we can assist you in your construction goals.