How to Test a Concrete Floor Moisture

2018-09-12

Concrete is a porous material, which means that a concrete slab would contain a fair amount of moisture. For new construction projects, moisture or liquid vapors trapped within a concrete floor can lead to installation delays and flooring damages during a floor’s lifecycle. Thus, it is important to find out how much moisture in the concrete floor. Here are the two most common types of test for concrete moisture.

Plastic-Sheet Moisture Test

The easiest way to determine if you have moisture that transmits through your concrete floor is ASTM D 4263 Plastic-Sheet Moisture Test.

You can do this simply by cutting a 16”x16” piece of plastic sheeting and taping down the perimeter with duct tape to the surface of your concrete floor.

Check the squares every few days. If you find moisture on the bottom, you have moisture in the slab. Moisture on the top, more common in a basement, is a sign of condensation from high humidity in the room. Moisture on both sides means that you have moisture in the air and in the slab. If none exists, then you should be fine. 

However, temperature and dew point can affect this test and a dry sheet test isn't necessarily a sure sign. Especially, you are planning to put an epoxy coating on the floor.

For a more accurate test, you might want to consider the next option.

Calcium-Chloride Moisture Test

A calcium-chloride test is used to determine exactly how much moisture have emitting from your concrete slab. You may need to order your calcium-chloride moisture testing materials online. Depending on the test kit you order, it should take about 3 days to complete the test.

By the way, before testing, you have to grind the concrete surface and conducting a simple pH test.

If the floor is emitting more than 3 pounds of water vapor per 1,000 square feet, you will need to first apply a proper moisture sealant before installing epoxy, or think about other types of flooring, such as carpets or tiles, which will not be affected by the moisture level in the concrete.

Just remember, of all the things that need to be considered before you decide on an epoxy coating or paint for your concrete floor, determining if you have a moisture issue is the first step. It’s easy and fairly quick to do and can save you from the disappointment and anguish of a failed floor coating.