A moisture meter is a handheld device that uses electrical impedance or capacitance to give a fast, non-destructive relative reading of moisture near the surface of a concrete slab.
Understanding Moisture Meters in Pre-Installation Testing
A moisture meter is a handheld electronic tool used to take a quick, non-destructive reading of relative moisture near the surface of a concrete slab. Contractors use them as a fast first pass before deciding whether more thorough moisture testing is needed.
How Moisture Meters Work
Most concrete moisture meters use electrical impedance or capacitance, sending a small signal into the surface and measuring how it changes based on moisture content. The reading is relative rather than an exact percentage, which means it is most useful for comparing different areas of the same floor to spot problem zones rather than as a precise measurement on its own.
Moisture Meter vs. RH Testing
A moisture meter gives an instant, surface-level, relative reading with no waiting period, while RH testing measures actual conditions deeper in the slab and takes at least a day to produce a valid result. Most contractors use a moisture meter to quickly scan a floor and flag areas of concern, then confirm those findings with RH testing before making a final decision on coating.
Practical Tips for Using a Moisture Meter on the Job
Scan the entire floor in a grid pattern rather than checking just a few random spots, since moisture can vary significantly across one slab. Pay close attention to areas near exterior walls, slab edges, and known low spots, since these areas often read higher. Treat a high reading as a signal to run a more definitive test like RH testing, not as a final pass or fail result on its own.
Also Called
Concrete moisture meter, impedance moisture meter
