In some respects, a professional moisture meter is a counterpart of sorts for home inspections or flood damage restoration.
Dependable and manufactured to work with you, the device – whether pin or pinless – lets you locate moisture and determine the extent of its presence.
But sometimes, no matter how well you’ve taken care of the device, a moisture meter’s accuracy may be noticeably askew.
Like any other measurement tool, professional moisture meters (albeit, rarely) can fall victim to issues that impact their ability to take readings. When this happens, ignorance isn’t bliss – continuing to take measurements all but guarantees a survey that isn’t accurate.
Knowing the signs of pin-type and pinless moisture meter accuracy issues and their causes helps ensure the integrity of a moisture survey’s results.
A highly sensitive measurement device, a moisture meter’s accuracy is critical for locating moisture and evaluating the degree of an intrusion. Small reading inaccuracies can have big impacts on the final results of an inspection.
When a meter’s readings are questionable, there are three sure-fire ways to know the device is not taking accurate measurements:
The golden standard for checking a moisture meter’s accuracy is verifying its readings by testing the same material multiple times. If the meter is functioning as it should, moisture level readings taken in succession from the same material will have virtually no difference.
Along the same lines as our previous point, a sure sign your meter is inaccurate is when its readings don’t match up with others. The same goes for ambient environmental conditions if you’re using a meter with a built-in hygrometer.
While there are nuances in the measurement scales of meters made by different manufacturers, readings taken by different meters (when adjusted) should be within the same range of each other. In other words, moisture content measurements should vary nominally between meters, regardless of their manufacturer.
One of the most obvious signs that your meter is giving inaccurate readings is through a quick inspection for damage. If a meter has taken a hard enough hit to cause visible damage – such as cracks in the case – or you can hear pieces moving around inside the device, odds are its measurements are no longer reliable.
While there are a variety of reasons for a professional moisture meter’s readings to be … a little off, the majority stem from environmental factors.
The most common include:
A naturally occurring substance that travels well with moisture, salt presents itself on materials where moisture is present. It’s most often seen as buildup on concrete flooring or along walls where moisture has leached through.
Salt is problematic for taking moisture readings with a pin-type meter for two reasons:
In both cases, salt impacts a pin-type moisture meter’s ability to take an accurate reading.
In modern construction, buildings are made using a wide variety of materials, with metal being one of the most predominant. Whether it’s screws, nails, pipes, wires, or support beams, metals can give false/positive readings for both pin-type and pinless moisture meters.
For pinless moisture meters, direct contact with metal to its probes gives readings that a material is wet. While non-penetrating moisture meters take moisture measurements in a different way for a different purpose, metal also interferes with their ability to locate moisture’s presence, also giving false-positive readings.
A material’s temperature is particularly troublesome for pin-type meters.
Why? Pin-type meters measure moisture through electrical conductivity and resistance.
When a material, such as wood, is warmer than the ambient temperatures around it, electrical conductivity increases, meaning the meter measures a higher moisture value. The inverse of this is true for colder temperatures.
Hand-in-hand with temperature comes surface-level condensation. When there’s a difference in temperature between the ambient environment and a material being tested, a thin film of moisture can form.
On lower-grade moisture meters (think the $20 devices sold at big-box retailers), surface-level moisture impacts readings for both pin-type and non-invasive meters, giving measurements of far more moisture than there actually is.
There’s nothing more frustrating than being in the midst of a moisture inspection and having your meter not work like it’s supposed to – especially when taking readings.
The best way to avoid being caught with an inaccurate meter is to be proactive. Before heading to a job site, a few simple tests can clue you in to the state of the meter’s functionality. Those same tests can also be run on-site, too.
When verifying a meter’s accuracy, you should:
If all else fails and your moisture meter’s accuracy is still in question, call its manufacturer.
In both home inspections and flood damage restoration, precise measurements are the most critical factor for addressing a moisture issue. Having a moisture meter that’s consistently accurate makes this possible.
Regardless of the type of meter you’re using, knowing the signs for and how to troubleshoot inaccurate readings helps you paint a true portrait of moisture within a space.
Check out our downloadable guide, How to Measure Moisture in Buildings, to learn about the finer points of inspecting for moisture.