Moisture testing is absolutely essential for your concrete flooring. Following the proper process prevents the products you apply from failing due to high moisture vapor content. This can happen with both new and old concrete. Radiant in-floor heating does not prevent you from having high moisture vapor.

It is important to understand that moisture testing takes 3 days or 60-72 hours. The Calcium Chloride Test is one of the most well-known tests to measure the moisture vapor levels in a concrete slab. It is the standard test used by the majority of flooring contractors in the United States. The American Society for Testing and Materials (ASTM) states that Moisture Vapor Transmission Rates (MVTR) of four pounds per 1,000 square feet over a 24-hour period is the maximum rate allowable to successfully cover concrete with adhesives, sealers, or coatings. Per ASTM F1869, test density is required to equal 3 tests in the first 1,000 square feet, with one additional test for each additional 1,000 square feet of the concrete slab surface. MVTR can be determined by comparing the weight of the calcium chloride in the test before and after the test time (60-72 hours). It indicates not just whether moisture is present, but the quantity and MVTR traveling upwards through the slab. It is recommended to follow all product instructions included with your Calcium Chloride Tests.

STEP #1: Identify how many tests you need, and plan out their placement across your flooring area. The test site should be at the same temperature and humidity expected during normal use. For example, 2,000 square feet (SF) requires 4 Calcium Chloride Tests (3 tests for the first 1,000 SF + 1 test for the remaining 1,000 SF).

STEP #2: Prior to placement of the tests, the test areas should be clean and free of all foreign substances. It is recommended to use a diamond grinder to prep each test area (20” x 20”) 24 hours prior to testing.

STEP #3: Pre-weigh each test with the lid on, using a gram scale accurate to 0.01g. Verify the starting Dry Weight that is printed on the test. Write on the lid the Start Date & Time you are setting the test. Under Plot No. write down the location you are setting the test. For example, NE Bathroom.

STEP #4: Remove the lid from the test and carefully place the test on the prepped floor space without spilling any of the calcium chloride. Place the lid under the open dish. Avoid mixing lids with dishes from other tests.

STEP #5: Remove the release paper on the plastic cover and immediately place the plastic cover over the calcium chloride dish and press firmly to make an airtight seal. Complete this step with all tests placed.

STEP #6: Leave the tests undisturbed for a minimum of 60 hours. DO NOT EXCEED 72 HOURS! Be sure to note the Start Date & Time the test was started and collect the test within this timeframe.

STEP #7: After 60 hours, and BEFORE 72 hours, have passed, remove the cover and replace the lid on the test dish. Make sure that none of the calcium chloride is spilled. Record the Ended Date & Time on the lid.

STEP #8: Using a gram scale accurate to 0.01g, weigh the test dish with the lid on. Record the Finished Weight on the lid. Take the Finished Weight in grams and subtract the Dry Weight in grams. This will give you the Weight Gain in grams. Take your Start and Ended dates & times and calculate the Total number of hours exposed.

STEP #9: Depending on the manufacturer of your Calcium Chloride Test, there are several online calculators available. For example, Taylor Tools Calcium Chloride Tests can be calculated online at: https://www.taylortools.com/calculator

STEP #10: Using the online calculator, input the Weight Gain in grams and the Total number of hours exposed. This will give you the final number you are looking for, pounds of moisture vapor emitted over 1,000 SF in 24 hours.

*IMPORTANT NOTE*Check your specific Product Data! Different coating products can handle various amounts of moisture vapor. For example, many standard epoxy primers cannot handle above 3 lbs. of moisture vapor. However, do not worry! We have special products that can handle up to 15 lbs. of moisture vapor and above!

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