Relative Humidity Testing
Relative humidity (RH) testing — performed per ASTM F2170 — measures the moisture content inside a concrete slab at depth. Unlike surface tests that only tell you what's happening at the top, RH testing reveals the true moisture condition throughout the slab, which is critical for predicting long-term flooring performance.
Key Takeaways
- RH probes are inserted to 40% of slab depth (for slabs drying from one side) or 20% (drying from both sides)
- Probes must equilibrate for 24 hours before taking readings
- Most flooring manufacturers specify maximum RH limits (typically 75-85%)
- RH testing predicts future moisture conditions, not just current surface conditions
- Readings above the manufacturer limit indicate the slab needs more drying time or a moisture mitigation system
Frequently Asked Questions
Most flooring manufacturers require ASTM F2170 and/or F1869 test results before honoring warranties. Installing over an untested slab is the leading cause of flooring failure.
ASTM F2170 requires 24 hours of equilibration after sensor installation. ASTM F1869 requires 60-72 hours. Plan accordingly before scheduling installation.
About the Author
Independent flooring inspector serving Southern California. Certified as NWFA Certified Inspector (#CP2416122), FCITS Master Inspector (#2031), NALFA Inspector, IFCII Inspector, and CFI University graduate. Specializes in forensic flooring investigations, moisture diagnostics, insurance claims, and expert witness services.
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