Testing moisture in a flooring system can be crucial for preventing flooring failures. However, when testing the moisture content (%MC) of a flooring system, there are a few things that can go awry, throwing off moisture measurements and compromising the end result.
What should you avoid when testing moisture in your flooring systems? Here’s a short list of some common problems that flooring experts have mentioned to Delmhorst in the past:
1: Using the Wrong Reading Scale and/or Species Correction
Flooring moisture meters come in many varieties, and some have different reading scales for different flooring materials—such as wood, gyp-crete, etc.
Using the wrong moisture meter reading scale for the wrong type of flooring throws off reading results. Even within a single reading scale, like wood, there may be a need to correct for the species of wood being tested.
This is largely because different materials have different physical characteristics that will impact meter readings. For example, pin-type meters that use electrical resistance to measure moisture might display different results in maple and pine floor samples that have the same %MC. This is because of differences in the electrical conductivity of these two types of wood. Pinless meters, on the other hand, might have their readings affected by the specific gravity (SG) of the material being tested.
Some meters have a function known as species correction that allows them to adjust readings based on species of wood being tested. Others have multiple reading scales for wood, gypsum, and other materials to let them be used in many different flooring systems.
When the wrong reading scale is used, moisture measurement accuracy suffers. So, at the start of any test, it’s important to verify what kind of flooring system is being tested and that the moisture meters used to test it have the appropriate reading scale—and are in that mode.
2: Scanning Metal Subfloor Materials with Pinless Moisture Meters
When using a pinless moisture meter for testing any flooring system, users have to be careful of any metal objects that may be present in the subfloor. Pipes, nails, staples, and other metallic objects can throw off moisture measurements taken with a pinless meter if they are in the scanning range of the meter.
This is largely because pinless meters check for moisture to a fixed depth (typically 3/4”) using an electromagnetic frequency. Any materials in the range of the scanning area will affect the reading. Metallic materials can have a large effect on the accuracy of the reading because of their density and electromagnetic properties.
So, when checking for moisture in subfloors, it’s important to know if metallic objects are present just beneath the surface. If they are, it may be necessary to use a pin-type meter to avoid false positives from metal objects in the subfloor.
3: Forgetting to Check the Accuracy of the Meter
Even the best-made flooring moisture meters can, over time, lose accuracy. There are many causes of this, such as damage to the testing medium, damage to the meter’s circuitry, issues caused by using the meter with depleted batteries, and so on.
So, before checking for moisture in a flooring system, it’s vital to test the accuracy of the moisture meter. The two most popular methods for doing this are to use a built-in accuracy check, or to use a testing device like a moisture content standard (MCS) or moisture block built specifically for the meter being tested.
Built-in tests are simple enough—the user puts the meter into the self-test mode and hit a button. If the reading matches what the owner’s manual says it should be, then the meter is accurate.
MCS and moisture block tests have the user place the sensor medium against a purpose-built testing device and take a reading. For pin-type meters, the MCS is a small device with two (or more) raised bumps for pins to be pushed against. Pinless meters use moisture blocks to push their scanning plates against for a test. The desired reading value should be specified in the owner’s manual for either the meter or the testing device.
It is important to note that MCSs and moisture blocks are purpose-built devices specific to a particular model of moisture meter. Using a moisture block made for one meter on a different one may skew the measurement.
4: Low-Quality Moisture Meters
Many professionals have been frustrated by their low-cost, but also low-quality moisture testing devices. These professionals have learned the hard way the meaning of the phrase “you get what you pay for.”
Cheap tools are often made with cheap materials to cut costs—meaning that they may have low-quality plastic, no replacement pins (for pin meters), or poor overall construction that affects the useful life of the meter. They’re also frequently less accurate, have fewer functions, and weak warranties.
A low-quality moisture meter is more prone to breaking on the job, and giving less accurate results. This, in turn, leads to frustration when trying to use cheap meters on a flooring installation job.
These are just a few of the things to avoid when testing moisture in your flooring systems. For more information about measuring moisture in flooring, check out our free guide!