Moisture testing is one of the most misunderstood steps in the concrete construction process. Despite improved standards and wider awareness, builders still make costly mistakes when it comes to evaluating moisture in concrete slabs.
These errors can result in flooring failure, warranty issues, and avoidable delays. Let’s look at the most common missteps—and how to avoid them.
Mistake #1: Relying Only on Surface Readings
Using handheld moisture meters alone is a fast way to get fooled. These tools measure surface-level conductivity and don’t account for deeper moisture, which is what really affects flooring adhesion.
Moisture at the surface can vary with ambient conditions like HVAC status or recent rainfall. But what’s happening 40% into the depth of the slab? That’s what actually matters.
For a full breakdown of how these tools work—and when they fall short—see Understanding Concrete Moisture Meters – A Comprehensive Guide.
Mistake #2: Skipping ASTM-Compliant Testing
Even experienced crews sometimes skip proper testing due to time pressures. But without following ASTM F2170 (RH probes) or ASTM F1869 (calcium chloride), test results won’t meet manufacturer or code requirements.
That means:
- Warranties could be voided
- Legal liability increases
- Flooring failures become your problem
Compliance isn’t just a technicality—it’s a shield.
Mistake #3: Testing Too Early
Concrete continues to release moisture as it cures. Testing too soon (especially before HVAC systems are operational) gives an inaccurate view of long-term moisture behavior.
Tip: Always stabilize the building to expected service conditions before conducting RH or MVER testing. That means closed windows, running HVAC, and steady humidity levels.
Mistake #4: Assuming “Dry to the Touch” Means “Dry Enough”
Concrete that feels dry may still have dangerously high levels of internal moisture. This false sense of security is a leading cause of floor failures, especially with vapor-sensitive materials like:
- Vinyl
- Rubber tile
- Epoxy coatings
- Adhesive systems
Moisture is invisible—and ignoring it is expensive.
Mistake #5: Not Documenting the Test Process
Verbal reports or cell phone snapshots don’t cut it. Proper documentation includes:
- Test locations and depth
- Environmental conditions
- Test method used
- Results and interpretation
This record protects your team—and supports your timeline—if issues arise later.
Final Thought
Moisture testing isn’t just about checking a box. It’s about protecting your build, your budget, and your reputation. When builders rush, guess, or assume, it’s the slab that calls the bluff. Know better. Test smarter.