The 10 Worst Mistakes You Can Make with a Moisture Meter
A moisture meter is a necessary and valuable tool, whether you lay down wood flooring, build furniture, or fashion violins. Whatever type of woodworking you do, you need to use the moisture meter properly or it’s not doing you – or your project – any good.
Listen, using a moisture meter isn’t rocket science, but there is a right way and wrong way. We covered the best practices for using a pinless moisture meter. Now it’s time to call out the most common and worst mistakes we see people making with pin or pinless moisture meters.
1. Measuring wood with water on it.
You’d think common sense would send up a red flag about trying to take a moisture measurement when the wood’s surface is wet. Apparently, some people think that since the meter is measuring moisture levels below the surface, surface moisture isn’t an issue. It is. Whether it’s condensation or maybe something spilled, any surface water on the wood will interfere with the meter’s reading.
If you see surface moisture, wipe down the piece of wood. Give it some time to dry, considering how much moisture you had to wipe off. Since there’s a good chance that some of the surface moisture got absorbed into the wood, you may want to consider how that will impact the reading if you don’t give the wood a good chunk of time to dry out. There are some meters that have been designed to minimize readings from the surface moisture of wood while others are highly sensitive to moisture at the surface. In some meters, only a slight amount of surface moisture can significantly disrupt the moisture readings.
2. Using a meter that’s out of calibration.
Using a moisture meter that’s not calibrated is like that old cliché, “Ask stupid questions, get stupid answers.” Instead, we say “Use an uncalibrated meter, get an uncalibrated reading.” It’s no good.
This raises the question of whether your meter is out of calibration. Many come with a “built-in” calibration check. However, anything that happened that could have potentially messed up the meter’s calibration – like dropping it or leaving it outside – could very well have messed up the internal circuitry used by that “built-in” calibration check test. In most cases, the only way to reliably check whether your wood moisture meter is calibrated is to use an external calibration tool. If it turns out that if your meter is uncalibrated, you’ll have to send it back to the manufacturer for recalibration. Hope you have a spare!
If you’re working with an Orion® moisture meter, you can recalibrate the meter in the field. It’s the only line of meters that you can recalibrate yourself. Every Orion wood moisture meter comes with a factory-paired recalibration tool, the On-Demand Calibrator. It’s so fast and easy to use; it’s simpler to just recalibrate your Orion moisture meter than to check whether or not it is calibrated. So if you’ve dropped your Orion meter – take a few minutes to recalibrate it, and you’re good to go.
3. Using the wrong species setting.
Both pin and pinless meters are impacted by the wood’s species. Different species have different chemical properties and densities, which impact how the meters read a board’s moisture content.
Always check before starting a new batch that the species setting on the meter is correct. Most wood moisture meters will have a species setting option. If it doesn’t, it should come with a correction table that you need to convert the meter’s number into the moisture content measurement. If you often work with exotic species, look for a meter with a broader range of species adjustments. If you only occasionally work with uncommon wood species or want to know the specific gravity for a subspecies, use one of the handy species tables from Wagner Meters to refine the accuracy of the reading.
4. Not identifying where metal is embedded in the wood.
If you have to measure moisture levels of wood that’s already been worked on, there may be studs or nails in places. Any metal that’s within the scope of the moisture meter’s pins or sensor plate may interfere with that meter’s reading. If there’s a question, use a stud finder or other tool to confirm whether metal is present. If it is, take your readings in other spots.
5. Using a moisture meter to detect mold.
Mold can cause major damage to wood, to say nothing of its potential negative impact on people’s health. Trying to find mold is worthwhile, but a wood moisture meter can’t actually detect the mold.
A moisture meter can tell you if excess moisture exists in an area. Based on those findings, you can then conclude whether or not it is highly probable that mold may grow in that area since a high moisture condition promotes mold growth.
6. Measuring moisture content at only one spot.
Wood meters measure the moisture at the spot where you’re using the meter. Moisture doesn’t exist evenly throughout the board or especially throughout a large batch of wood. You want to take readings from multiple spots so you can get a full picture. You may find some outlier readings. If that outlier spot had been the only reading you took, then you’d be working with an inaccurate understanding of that wood’s actual moisture condition. For example, it’s very common for boards to have a different moisture content near the ends of the board than the middle.
The sample principle holds true when you’re measuring moisture in a stack of lumber. The larger the piece of wood or the bigger the stack, the more readings you want to take. With a larger set of data points, you can be more confident that you’re making decisions based on an accurate reading of the piece’s or batch’s overall moisture condition.
So let’s be realistic. If your meter makes it difficult and time-consuming to take a single reading, you’re probably not going to take enough readings. Pinless meters are much easier and faster to use than pin meters, which means you can efficiently and easily take all the readings you need.
7. Don’t leave your moisture meter in the rain.
This seems like another “duh” mistake, like measuring wood when it’s covered in moisture. But you’d be surprised how often people leave their meters exposed in the back of their trucks and then Mother Nature does her thing. Just because meters can read moisture in wood doesn’t mean they’ll work if moisture leaks into their circuitry.
When you’re not using the meter, put it in its case and store it someplace dry.
8. Buying a cheap moisture meter for your business.
Wood moisture meters can vary in price quite a bit. The accuracy, function quality, and range of features will vary greatly among moisture meters and the price of the meter will often reflect those differences.
If you’re an occasional hobbyist, and can afford to have projects fail every once in a while, then a simpler moisture meter for $50 may work for your needs. However, if woodworking is your business, then you need to make the right investment in your tools of the trade. Your wood moisture meter is an essential tool for ensuring the quality of your work and by extension, your reputation.
If you regularly work with exotic species, get a meter with an extended species setting. If you work with woods with a variety of thickness, make sure your meter has dual depth options for readings. If you work with large batches of wood, juggle multiple projects at once, or are a quality assurance manager at a plant, look for a moisture meter with top-notch data collection and management tools.
In other words, if your livelihood depends on how you handle wood, your ROI on a top-shelf wood moisture meter will be incalculable.
9. Expecting accurate moisture readings for non-wood materials.
Many wood moisture meters have a setting to take readings from non-wood materials. This feature can be helpful, but only if you’re clear on what information the meter is giving you.
Wood moisture meters can give you a quantitative moisture measurement for a piece of wood — that means an absolute number. For most other materials, the meter returns a comparative reading of moisture, not a measure of the exact moisture content; these measurements can be helpful, however, to determine if one area is higher or lower in moisture content than another.
When you want to use the meter on another material, say drywall, you need to switch it to a different work mode. On the Orion line of meters, this work mode is called “relative moisture mode.” The keyword here is “relative.” This function will use similar language on different meters, because, in this non-wood mode, the meters are only assessing whether the spot has more or less moisture than another known dry spot.
After you switch the meter to the relative mode, first use it on a spot you’re confident is dry. Then take a reading on the spot(s) where you think there may be excessive moisture. If you get a higher reading in another area, you can be confident that the areas with higher readings may have more moisture. Meters may use a 10- or 100-point scale to indicate the relative readings. Others may use color indicators.
10. Not using a moisture meter at all.
I take it back. This mistake wins the “well, duh” award.
You cannot eyeball wood’s moisture levels. Not for a single piece of wood and certainly not for a batch of wood. A dry surface doesn’t mean that the wood is adequately dry, or that it’s ready to be installed as flooring or fashioned into furniture. Waiting a certain amount of time for the wood to acclimate is no guarantee that your wood, sitting in your specific environment, has in fact fully acclimated.
In fact, after all the apparent moisture and liquid water within the wood has evaporated is the most critical time to know exactly what the moisture content of the wood is. When all the free water (i.e., liquid water) is evaporated, the wood starts losing the water vapor bound up in its cell walls. It’s the movement of moisture in the wood’s cell walls that impacts the physical size and integrity of the piece.
Without a moisture meter, it is impossible for you to know whether the wood has reached the MC level that correlates to the point of equilibrium moisture content (EMC) with its intended surroundings. Dr. Eugene Wengert, professor and specialist in wood processing at the University of Wisconsin-Madison’s Department of Forestry, states that wood should be dried to an MC that’s within two percentage points of the EMC where the wood is going to be used.
Well, you can use tables and formulas to calculate the target EMC for the end-use environment. But how are you going to be able to tell whether that wood’s moisture content is within 2% of the end-use environment’s EMC? You’re not — not unless you have an accurate reading of the wood’s MC from a quality wood moisture meter.
The process for ensuring the wood you’re working with has reached an acceptable moisture condition is pretty simple: Use a high-quality wood moisture meter; use it consistently and properly. So be the woodworker that avoids the moisture meter worst mistakes, and save yourself the heartache of failed projects.
Last updated on October 7th, 2020