Many “experts” claim to know how to correctly test for moisture in wood floors and which moisture meter is the best.
On the other hand, other flooring professionals use the cheapest meter without researching what’s best for their job.
When it comes to your projects, how do you test for moisture in wood floors?
3 Reasons To Own a Good Moisture Meter
To start with, it’s important to know why a good moisture meter is worth the investment.
- Hardwood floors should never be installed before first checking their moisture content. This is needed to ensure the floor is not too wet or dry. Additionally, test the subfloors to determine the range of acceptable moisture content prior to hardwood installation. (See NWFA’s article to learn more.)
- Moisture meters prevent future claims by ensuring the moisture content of wood is right for the installation area.
- If a problem occurs, a moisture meter can determine what is going on. Testing the floor’s moisture is a great way to find the cause of gaps, squeaks, and other issues.
What Moisture Meter is the Most Accurate?
A few years ago, on a wood flooring inspection, I used two different meters and got two different moisture readings – testing the same boards.
Is this normal? Let’s find out!
First, let’s look at the technology to answer this question.
There are two basic types of electronic devices on the market for measuring moisture in wood – pin and pin-less. A third type measures relative humidity (%RH) primarily in concrete. Be sure you’re using one meant for wood flooring.
“Non-destructive” aka pinless or surface meters use a flat sensor pad that measures 3/4 inches into the flooring. The science – the meter measures the electromagnetic frequency of the returning radio waves from those transmitted from the unit.
“Destructive” or pin meters measure electrical resistance between two conductive pins inserted into the wood. Pin meters with an extension attachment measure up to several inches.
Did you know that moisture meters don’t actually measure moisture?
How do these qualify as testing moisture?
The answer is gravimetry!
Gravimetric testing determines the gravity or weight of water in a material (such as wood) by evaporating out the water. The wood first is weighed, then evaporated, and then weighed again. This data calibrates the meters so that they can accurately measure the “moisture equivalence” by species.
This is why proper species calibration is essential for each electronic device.
Do all brands of moisture meters use this technology as a baseline?
Reputable manufacturers include this in their documentation. Consult their website to confirm their requirements and specifications. A few brands we recommend include Lignomat, Delmhorst, and Wagner.
To summarize, the accuracy of a meter is determined by how well it is calibrated, not by if it is pin or pin-less. The next important thing to consider is what you are testing.
What Type of Meter is Right for the Job?
Each meter has their place in a flooring pro’s toolkit.
A surface meter is ideal for quickly checking many boards without causing damage from pin holes prior to installation.
A pin meter is best for testing installed flooring. You can start with a surface meter, and move to a pin meter if there is a spike on the surface meter. Since the pin meter is more invasive, it can better read the extent of moisture penetration into the wood and subfloor.
Surface meters are great for fast and easy, “general” checks. However, if not on the correct species setting, they can report incorrect readings. The best meters can be programmed for various species and their individual gravity.
Remember – the more precise the species setting, the more accurate the results.
Along with this, manufacturer support is vital, as species settings can change.
Some manufacturers do not support exotic species like bamboo, Brazilian Walnut, or Acacia flooring. So, consider the level of technical support and expertise when choosing your next moisture meter.
Using Two Meters on the Same Job
In the earlier example, I had two moisture meters giving two different readings.
The first reading with the surface meter showed high moisture. When the pin meter was used in the same location at 1/2″ to 3/4” depth, the moisture reading was within the normal range (6-9%).
In this case, the high moisture reading from the surface meter was exactly that: on the surface. Excessive humidity levels in the home caused the high reading, which a simple thermo-hygrometer also detected.
A hygrometer is a simple, but useful tool when used in conjunction with moisture meters.
Does the brand of moisture meter matter?
The accuracy of test results may vary, based on these factors:
| Surface Meters | Pin Meters |
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Moisture meters and hygrometers are effective and essential for every professional flooring retailer. Becoming familiar with their use, these tools will instill confidence in everyone involved from builder to homeowner, that quality is a priority with flooring professionals.
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