How to Perform a Moisture Test for Epoxy Floor Installation

What You'll Need
Broom and dustpan
Shop vacuum
Moisture test kits
Alkalinity test kits
Calculator to determine vapor transmission
Penetrating sealer
Mop and bucket

Before you install your epoxy floor finish over a concrete subfloor, a moisture test is recommended. Excess moisture rising to the surface of concrete will destabilize your epoxy floor and can buckle it, or lift it right off the concrete. Excess alkalinity will eat epoxy coating, causing it to bubble and split. Follow the steps outlined below to perform a moisture test prior to an epoxy floor installation.

Step 1: Clean and Dry the Concrete Floor

Sweep, vacuum and dry the concrete floor with a shop vacuum to ensure it is emitting as little moisture as possible.

Step 2: Check the Room Temperature and Humidity

Moisture tests are most reliable when done in an air temperature of 65 to 85 degrees F (18 to 30 C), with relative humidity levels not exceeding 60 percent.

Step 3: Set Up the Moisture and Alkalinity Test Kits

Use one test kit for every 333 square feet of concrete floor space, that is, 3 per 1000 square feet. Set the test kit on the concrete floor and cover it with the bright red plastic dome cover provided. Note the weight of anhydrous calcium chloride in the dish when you start the test period.

Step 4: Check the Vapor Transmission Rate

After at least 60 hours, and no more than 72 hours, remove the dish of anhydrous calcium chloride from the test kit dome. You will have to cut off the dome cover to do this. Compare the weight of the calcium chloride dish following the test with its weight preceding the test time period. You can have the calcium chloride weighed through the agency where you purchased the test kit, or you can buy a precision weigh scale along with the test kit to obtain immediate results. The weigh scale is useful for many other do-it-yourself projects around the home.

Step 5: Safe Vapor Transmission Levels

For new concrete the vapor transmission level cannot be greater than 3 pounds/1000 square feet. This means each of your three test kits cannot have picked up more than 1 pound of moisture each. Many new concrete floors, however, test out at between 10 and 15 pounds of water vapor per 1000 square feet, or 3 to 5 times the recommended maximum limit.

Step 6: How to Reduce Your Floor's Moisture and Alkalinity Levels

The best way to reduce the moisture level in your concrete floor is to cure the concrete for at last a month. The recommended curing time is 3 to 4 months, in warm weather conditions, and up to 6 months if the concrete was laid in the autumn. Once the tested moisture level is at the safe maximum, you can pour your epoxy floor onto the concrete. If time is of the essence, apply a penetrating sealer to your concrete floor surface. Choose a sealant that will also reduce the alkalinity or causticity of the concrete, caused by the lime used in making it. Apply the penetrating sealer with a fiber mop, according to the manufacturer's instructions.