The Douglas fir.
A sugar pine.
The western hemlock.
By appearances, these coniferous trees seem mostly the same. Tall, covered in needles, and boasting a pine scent, there’s no question the three species of trees are closely related. When milled into lumber, the story is much the same for the softwoods – despite some small visual differences, planks from each tree are extremely similar.
The fact remains, however, these trees and their byproducts are different, even if it’s just by a little bit. Nuances between wood species – no matter how small – can have big impacts in certain situations, such as wood flooring installation. Though the aforementioned softwoods would almost never be used in wood flooring, paying careful attention to the minute differences between them applies the same as it does with hardwoods, such as oak, cherry, or maple.
When putting in a new hardwood floor, one of the most important considerations is how the lumber interacts with moisture. Nothing ruins an expensive hardwood floor quite like a moisture issue.
Professional moisture meters bridge gaps between species allowing for accurate readings regardless of the type of wood being measured. Calibrated to account for what differentiates wood species, a professional moisture meter helps ensure a reliable reading every time.
Though moisture meters are designed to take measurements across a variety of materials, most meters' readings are calibrated for wood.
Many professional moisture meters use wood moisture equivalency (WME) as the base when measuring other materials than wood.
In some schools of thought, wood is considered a "living" material as it's very reactive to ambient conditions -- particularly with moisture. Naturally hygroscopic, wood absorbs and releases moisture until it reaches the same level as its environment or materials it's in contact with. Other materials (think: plaster or drywall) do the same. Thus, if moisture presence is high enough to be considered excessive for wood, it's a good indicator of issues, such as mold or rotting, for other materials.
However, WME readings are somewhat fluid; they do require context about the material being tested to interpret correctly. For instance, high moisture content in brick is not as concerning as it would be for drywall -- brick isn't damaged the same way drywall is by moisture.
While wood sets a baseline measurement standard for gauging moisture presence in other materials, there are differences in how wood species react to and hold moisture.
Different types of wood have varying levels of density, porosity, and hygroscopic properties that can affect the accuracy of moisture readings. For instance, oak typically has a higher equilibrium moisture content (EMC) -- or the point at which it's reached a balance with its environment -- than cedar. Oak is also denser than its coniferous relative. These differences mean that an oak floor may have a higher moisture content reading than a cedar floor, even if they're in the same room with the same humidity levels. And at the same time, both boards can appear dry to the touch despite having a significant difference in moisture content.
A wood species' chemical composition also comes into play for moisture measurements. Wood that has a higher salt content will give higher moisture readings with a pin-type moisture meter as it's more naturally conductive.
To account for these nominal differences and ensure accurate readings, moisture meters often come with species-specific calibrations. This allows professionals to select the type of wood being tested and adjust their meter accordingly for more precise measurements.
Creating species-specific calibrations is a process that involves testing and gathering data on the electrical properties of wood samples from various species. This data is then used to create calibrations that allow a moisture meter to accurately measure the moisture content in a particular type of wood.
It's important to note that these calibrations may need to be updated or adjusted as the characteristics of the wood can change over time, such as with changes in growing conditions or processing methods.
To create wood species calibrations, moisture meter manufacturers use the oven-dry test method, a six-step process.
Creating Species Calibrations in 6 Steps
The process is repeated multiple times with multiple pieces of wood for various amounts of drying time. Data collected from each test run is used to build up a chart that shows a wood species' electrical resistance at various moisture levels. That information is later programmed in a professional pin-type moisture meter, which automatically makes specific corrections by converting its resistance readings to moisture content.
Did You Know ... Protimeter moisture meters are pre-loaded with calibrations for more than 140 wood species?
Correctly identifying and adjusting for the type of wood being tested helps prevent costly mistakes -- such as choosing the wrong flooring for a room with high moisture levels or different types of subfloors. i.e concrete, gypcrete. or plywood because of incorrect measurements.
There are two options for making species corrections: manually or automatically with a meter.
(Using this method, you'll need a species calibration chart)
In most cases, the differences between wood species and their ability to hold moisture are inconsequential.
Consider a flood damage restoration scenario. After a flood, an inspector isn't necessarily concerned about the species of wood they are testing. Rather, they're more interested in quantifying and qualifying the extent of moisture presence in a space. In almost all instances, an inspector won't be adjusting their meter to a species of wood.
However, wood flooring installation -- and even woodworking projects -- are significantly different. Even the smallest nuance between wood species matters.
For example, if a moisture meter reading for an oak board is not calibrated for its species, the reading may be too high and lead to incorrect assessments of whether the wood is ready for installation. After being put in, this could result in warping, cracking, or other damage to the finished project.
Similarly, in woodworking projects where the moisture content of the wood needs to be controlled for glue adhesion or finishing processes, species calibration ensures more accurate and consistent results.
Though there are nearly 100,000 species of trees on the planet, taking accurate moisture readings among the most common isn't difficult with a professional moisture meter.
With a quick adjustment, your meter helps preserve precision regardless of the wood species you're working with.
Download our guide, “Measuring Moisture in Buildings”: