Key takeaways
- Moisture vapor can push a coating off from below.
- Plastic-sheet tests are a rough check; meters and in-slab tests are better.
- Moisture-tolerant primers can protect moderate readings.
- Never coat a visibly wet slab.
Why moisture matters
Concrete is porous. Water vapor that moves up through a slab can push a coating off, creating bubbles, blisters and eventual delamination. Slabs without a vapor barrier, below-grade floors and new concrete are the most at risk.
Simple checks
The tape-down plastic sheet test, a square of plastic taped to the slab for a day, shows condensation or darkening if moisture is moving. It is a rough check, not a measurement.
Professional tests
Surface moisture meters give quick readings. Calcium chloride tests and in-slab relative humidity probes give numbers a coating system can be matched to.
What we do about it
Moderate moisture can be handled with a moisture-tolerant primer. Severe moisture needs the source fixed: drainage, gutters, grading or a waterproofing solution. We will not coat a floor that is not ready.
Related services
Ready for a firm answer on your own garage? Design your floor or call 800-207-0499 for a free estimate.