For many professionals, moisture meters are a must-have tool for their work. From the farmer who tests the available moisture in soil for irrigation, to the flooring contractor testing the moisture in wood flooring to make sure that it is not going to cup, warp or buckle, to the restoration specialist trying to make sure that a building is truly finished drying out and free of mold/water damage hazards, moisture meters are necessary to all of these hard-working professionals.
When used to test a given material, whether that material is wood, concrete, soil, hay, or even fiberglass insulation, the moisture meter interprets the readings and provides the user a numerical value to let them know the moisture content of the material being tested. However, not all moisture scales are the same. Sometimes, a moisture meter provides a reading that is measured as a percentage of moisture content, while others provide a number that represents a single point on a reference scale.
To understand what the numbers that you get from a moisture meter really mean, it’s important to know what the different moisture meter scales are used for and what they indicate.
The Reference Scale
One of the most commonly used scales is the reference scale. Unlike the wood, hay, or drywall scales, a reference scale reading does not provide an actual moisture content percentage (%MC) reading for the moisture content of the object being scanned, but rather a relative number between a minimum and a maximum value. For example, some reference scales go from 0 to 100, while others go from 0 to 300. This is part of what makes a reference scale sometimes difficult to work with, as there is no standard measurement, it’s all in reference to some other value.
That is not to say that reference scale meters are bad or without their uses. Each reference meter’s manual should provide you with an idea of what different measurements mean for that moisture meter in the materials you’re checking. Even though not a measurement of %MC (even on a 0 to 100 scale), a reference scale reading is useful for getting a general indication of whether the moisture in a given material is high or low. Testing an object that you think may have moisture against a value from one that you know is dry can be an excellent way to use a reference scale meter to evaluate moisture.
The biggest benefit of a reference scale meter is that it can be used to measure the moisture of many non-wood materials. Moisture meters meant for wood have an actual wood scale for that.
The Wood Scale
Probably the most common moisture meter scale aside from the reference scale, the wood scale actually provides a quantifiable moisture content percentage in wood. The reason we specify that this %MC reading is in wood is that wood moisture meters are calibrated specifically to provide %MC in wood and only wood (typically a specific species such as Douglas fir). Other materials would have different properties from wood, which would throw off moisture content readings.
Most moisture meters for wood are calibrated to cover a %MC range of 6% to 40% moisture content, but this may change for specific models and manufacturers. Since different species of wood have different electrical resistance and specific gravity, wood species correction charts are frequently provided with moisture meters to allow users to adjust their reading results to account for these differences.
When it comes to other building materials, such as concrete or drywall, the differences between these items and wood are so vast that a correction chart will most likely not be reliable enough to provide a %MC reading. Instead, these other materials tend to use a reference scale to provide an indication of moisture content. However, there are specific %MC scale meters for drywall from Delmhorst.
Typically, drywall is measured using the reference scale, where the user takes a reading from a dry sample first to get a reference number and then measures their drywall and compares the two readings to see if the drywall is moisture-compromised. However, with a moisture meter that has a drywall scale, you can get an actual %MC reading from your drywall. This can be a huge advantage.
Currently, drywall is considered moisture-compromised if it has a %MC of more than 1%. Moisture meters such as the TechCheck PLUS have the ability to read %MC in drywall from a range of 0.1% to 6% to let you know for certain if the drywall is at risk of developing mold or not.
Moisture meters for hay use a %MC scale similar to what a wood moisture meter provides, but calibrated for hay instead. Hay meters typically measure moisture from 6% to 40% in hay stacks or bales to let farmers know if their hay is at risk of spontaneous combustion or losing its nutritive value.
In hay, a difference of just two or three percent in the moisture content of a bale can mean the difference between top-quality feed and having to explain why the silo went “boom,” so the accuracy offered by a %MC reading is necessary for hay.