CONCRETE MOISTURE TESTING NOFMA PROCEDURES​

There are several methods to test the slab for high moisture. Moisture testing only confirms current levels that are currently present and does not forecast future levels.
What is the acceptable moisture limits in concrete before installation of wood flooring?

1. Moisture

a. Calcium Chloride test – 2 test kits per 1000ft. Test center of floor and exterior wall areas. If the concrete tests higher than 3 lbs, the slab is not acceptable and the glue may not bond well.

b. Phenolphthalein KIT – Chip the concrete and apply 3 or more drops of the solution to the test area.
If the color changes to pink or red, the presence of moisture is indicated. Test several areas especially near exterior walls and walls containing plumbing. Moisture content must not exceed 3% as read on the upper scale of this meter.

c. Tramex concrete Moisture Meter – used to determine whether the moisture in the concrete is acceptable, ready to begin installation. Moisture not to exceed 4.5% (Surface type meters will only measure moisture at the top 1 inch of the slab.) New slabs typically must cure for 90 days prior to installation.

d. Plastic sheeting and Duct tape method – This test only establishes the presence of moisture. Meters establish the true levels. Duct tape a 18 inch square piece of 6mm clear sheet plastic on the concrete floor. Ensure that the plastic is airtight then set a table lamp next to it. If after 24-48 hours droplets of water exist between the plastic and cement, a moisture barrier will be required. As a precaution, We recommend using a moisture vapor barrier whether or not moisture is present due to potential changing conditions. For more information, go to www.NOFMA.org.

2. Sealers

a. Determine if concrete sealers have been applied and remove by scarifying the surface as recommended by the adhesive manufacturers instructions. Urethane flooring adhesives will not adhere to concrete sealers.