Before installing any type of flooring on a concrete subfloor, you should always check for moisture, even if the surface looks and feels dry. Concrete can hold and release water vapor long after it's cured. If not addressed, the sneaky and quiet moisture can and would permanently damage your flooring. This will means costly repairs as you would have to replace a part of, if not, your entire floor.
Common Ways to Test Moisture in Concrete:
1. Plastic Sheet Test (Quick and Easy DIY Method)
- Tape a clear plastic sheet (approx. 2’x2’) tightly to the concrete surface.
- Leave it sealed for 24–48 hours.
- If condensation appears underneath, your concrete has a moisture issue.
2. Moisture Meter Test
- Use a moisture meter designed for concrete.
- Readings above manufacturer-recommended levels mean you’ll need a moisture barrier or breathable subfloor solution.
3. Calcium Chloride Test (Most Accurate for Vapor)
- This test measures moisture vapor emission rate (MVER) in lbs/1,000 sq ft/24 hrs.
- Ideal if you're installing sensitive flooring like laminate, vinyl, or engineered wood.
- Often required for warranty compliance for professional installations.
Why Moisture Testing Matters:
- It can protect your flooring from warping, mold, or adhesive failure,
- Help you determine the right underlayment or subfloor system,
- It's usually required by flooring manufacturers before installation.
Bottom Line:
Moisture in concrete isn’t always visible, but almost always there. A simple test now can save you from health issues and expensive repairs and replacement later.