Engineered Planks %MC

Measuring the Moisture of Engineered Floor Planks

Engineered floors have become very popular during the past few years. They are more economical than solid hardwood floors and can be more stable. When it comes to measuring the moisture content, engineered floors present a problem.

First, some general technical information about how moisture meters work and what the particular problem is, when measuring engineered floor planks.

Then, how to apply the measuring technology to measure moisture in engineered floors.

In the floor industry pin and pinless meters are both used. The calibration of all wood moisture meters is based on oven tests, which are performed with solid wood pieces.  Moisture meters indicate percent values based on the dry weight (0% moisture).

An accurate percent value is only achieved, when the moisture meter is programmed to correct for the wood species of the floor planks. That is true for all pin and pinless meters. The meter manufacturers provide listings for their moisture meters for the most common domestic and tropical wood species.

We recommend pinless dual-depth meters with a depth setting of ¼” and ¾” to measure engineered floors.

So, what is there to do, if you want to measure the moisture of an engineered floor with a pinless meter. Since we are not dealing with a solid floor, the question is, which correction setting has to be chosen to obtain the correct moisture percentage. Should you choose the setting of the wear layer and use it for the entire plank, top to bottom.

The problem is easily understood, when you look at, how pinless meters work. Some people think, because they are sitting on top of the surface, they only measure the surface. Some people think, because the measuring depth is ¾”, they only measure at that level.

Instead, pinless meters indicate the average moisture within their measuring field. If the measuring field is larger than the material to be measured, measurements are too low. They can also be too high, when the measuring field includes the material (concrete) below the floor plank. A dual-depth pinless meter is pictured below with 2 separate measuring fields. One measuring field reaches from the surface down to 1/4” deep, the other measuring field includes everything to ¾” deep. The average moisture in the field is indicated.

Measuring field of pinless dual-depth moisture metersThe engineered Maple floor in the photo consists of a Maple wear layer 2mm, and  7-ply Birch Plywood  as core Layer 10.5mm thick.   The ¼” is the only depth, where the engineered Maple floor plank is completely within the measuring field. Depth ¾”cannot be used for any floor planks less than ¾” thick. Even within the ¼” is a mixture of Maple and Birch plywood and the question remains, which correction setting should be used Maple or Birch?

To determine the right correction setting would be easy, if this were a solid floor. It becomes tricky, when measuring engineered floor planks.

There are endless possibilities how engineered floors are put together. The thickness of the wear layers are usually between 1-4mm. The core and the bottom layer could be of different thicknesses and materials glued together.  

Measuring engineered floorsFloors in this photo were Engineered Oak, Maple and Hickory floors. Note even the core is different.

Measuring engineered floors.

As pointed out above, the difficulty is to determine the right correction setting for the moisture meter, since different materials of varying thicknesses are glued together. Even engineered Maple floor differ in composition from one manufacturer to the next.

Composition of engineered floorPinless Meter: We determined the following settings with the method described below. From the top, measurements can be taken with correction setting  #68. Placing the Ligno-Scanner on the bottom, the setting should be #86. All measurements were taken on the  ¼” depth. Both correction settings are different if measured from the bottom or from the top. Both settings are not the same as indicated in the manual for solid Maple and solid Birch.

Here is how these correction settings were found.

First step, a piece of floor is needed with a known moisture content.

Let’s assume, we already found a sample piece of the engineered floor and we know that the moisture content of the sample is 8.5%. Later we will explain how to determine a test sample with a known moisture content.

 Assuming you had a test sample of the floor at 8.5%, and now you want to find a correction setting for your pinless moisture meter. Set the meter to ¼” depth and take a measurement on correction setting  # 50. The percent value indicated at the meter is for sure higher than the 8.5 %. Next you change the setting from # 50 to a higher setting and take intermittent measurements until the indicated moisture percentage is 8.5%. The setting, which gave the 8.5% reading can be used in the future, when measuring the wear layer of the same kind of engineered floor planks.

For the Ligno-Scanner SDM the following numbers were found

Correction settingIndicated moisture percentage
#5011.8
#5510.6
#609.6
#658.8
#688.5

If the bottom of the floor plank should also be measured, you have to repeat the procedure described before. Again, you assume the floor plank is well acclimated at 8.5%. Then the Scanner is set to ¼” depth and the species correction # 50. Then change the setting until the moisture percentage is 8.5%.

We found some engineered floors to have the same setting for wear layer and core. However, that in most case, top and bottom required different correction settings.

Just a note, the procedure described above only works, when the pinless meter settings are based on the specific gravity of the wood. All Lignomat pinless meters have correction settings based on specific gravity, numbers between 30 to 100 or 0.3 to 1. The other important factor when using any pinless meter is, that the user has to put slight downward pressure on the meter, when taking measurements. It is recommended to be about 8 lbs of pressure.

This procedure does not work for pin meters, since the correction settings for pin meters are not based on specific gravity and are not a linear sequence of numbers. We found for pin meters, that measurements were higher than expected. Lignomat pin meters produced better values on correction setting #1 less 2%.

Determining the moisture content of the test sample.

The last question is, how do we know, what the moisture content of the test sample is. This can only be determined, when we know, that the test sample has been kept for a few weeks in a stable environment.  If the test sample is kept in a stable environment, it will acclimate to a certain moisture value depending on the relative humidity and ambient temperature. The stable environment could be a climatized show room or a storage area in the manufacturing facility. A thermo-hygrometer can show, what the relative humidity is.

 The floor manufacturer and the floor dealer have a definite advantage over the installer and even more so over the inspector. They can keep sample pieces for a few weeks in a stable environment and use the above described method to measure the test sample. A thermo-hygrometer can show, what the relative humidity is.

 The EMC chart below gives the corresponding moisture percentage for any ambient relative humidity and temperature.

Relative Humidity EMC Table

Example: If the relative humidity stays around 45% and 700F , the test sample will acclimate to 8.5%.

A wood floor is considered stable, when measured moisture values are 6-9%. Moisture varies depending on the region in the US, 6% and below for dry Colorado, 9% and above for humid Florida. When an HVAC system is in operation, the values should stay within 6% to 9%.

If you want to verify the so found, assumed moisture content (8.5% in the test sample), then you could measure some solid floor in the same area and see if that floor has the same moisture content.

Floor manufacturers and dealers could make it easy for the floor installer and inspector, if they would provide the correction settings for engineered floors, especially if the setting is different from the wood species setting for the wear layer.

Ligno Scanner settingsSetting Ligno Scanner SDM
This engineered floor went through the procedure described above in our office. The average moisture content of wood products in our office is about 8.5%. For this particular engineered Hickory floor we found that the setting #74 is correct. Even measured from the bottom, the setting #74 was correct. Actually the setting for a solid Hickory floor is also # 74.  The floor was acclimated for 4 weeks. During this time we took some moisture readings on setting #74. However the measurements never changed, which indicated the floor was well acclimated and the #74 setting is If the setting for the engineered floor is unknown, he installer can use correction setting #0. This is a reference scale which allows the installer to find out if the floor is acclimating. By recording the indicated values at the end of the install, base values are available for any investigation later on.   Noteworthy is that the percent sign behind the indicated value of 11.6 missing, indicating that #0 is only a reference scale.
Ligno DuoTec BWThe inspector of course does not have the luxury of time to acclimate sample pieces. He may not even have a sample piece. Or he may not know the species of the floor he has come to inspect.   If no records are available of any previous moisture testing, and the species of the floor planks are not known, the inspector can also use setting #0. On the setting #0, he can determine if all floor planks have the same moisture. He also has created a base to compare future measurements.

If no recommendation for a correction setting is available, the installer can take measurements with the reference scale #0 available in the Ligno-Scanners. The indicated values are not moisture percentages. However, the values indicate variations and can serve as a reference value to go back to and compare, should any problems occur at a later time.

The inspector may have an additional problem, if he is called to inspect a floor and cannot determine the wood species of the floor planks. This happens even for solid floors. When no information is available, the inspector can use the reference scale #0. This allows him to compare different areas and to create a record for future inspections.

Any report about moisture measurements should contain, which meter was used, the correction setting, the measuring depth and the sensitivity (range for the reference scale; 0-10, 0-100,…), and the location, where the measurement was taken (photo).

A moisture meter is an essential tool for all wood floors, whether they are  engineered or solid.

For questions,

Please contact

Grete Heimerdinger

Lignomat 800-227-2105

Monitoring Problem Areas: easiest & simplest leak surveillance

Detection is the first step to prevention, here is an inexpensive solution


If it would not be for mold growth on one hand and shrinking and warping on the other hand, nobody would worry about moisture in wood. Shrinking and warping look ugly. Mold however, is a hazard for a building, home or office and a health hazard for the people who live or work in the building. Mold in our homes can cause major health issues. Many people live with mold and do not even realize how it is affecting them. Mold can cause upper respiratory problems such as coughing, wheezing, red itchy eyes and asthma like symptoms. Some people with immune system issues will be much for susceptive to mold. Mold will grow in moist conditions that can arise from leaks in a roof or window, pipes, water from plants, or even flooding. Mold remediation can get very costly. It is important to fix the problem and to make sure it does not come back. Sometimes it can be a seasonal problem which occurs when there is a lot of rain. We have a cost effective package that will help you monitor hard to reach areas such as in a crawl space, in a wall cavity, or behind a sink. The S-11 package comes with our mini-Ligno SD/C moisture meter which can read wood and sheetrock in MC%. The meter has a wide measuring range 6-45% which allows the user to measure and monitor the moisture of problem areas. Here is an example of a specific application: How to check moisture levels in a crawl space without having to “crawl” into the space. You need a moisture meter and a long enough cable to reach down to the crawl space. After installing the cable in a floor joist of studs in the crawl space, the other end of the cable is left in a place on the first floor, easy to reach. For measurements, the cable is plugged into the meter and instantly a moisture value is indicated. That value should stay below 16% to prevent mold growth. Items to be ordered are package S-11 (moisture meter mini-Ligno S/DC) or package M-11 (moisture meter mini-Ligno MD/C) includes one cable 6ft long and 1 pair of probes for wood or pins for drywall.
S-11 package wood and drywall – List $178.00
M-11 package wood and drywall – List $105.00 
How one customer used the S-11 package to monitor moisture damage.
Here is an example of how one of our customers used the the S-11 package (moisture meter, cable and wood probe)After setting the probe in the wood and connecting the cable (photo 1), the cable was runup through the floor to a closet in the center of the first floor. That way, the moisture content can be checked any time, without having to go back under the house (Photo 2).
The moisture can now be monitored throughout the seasons and it can be noticed weather or not long periods of rain will affect the moisture content in the joists. I will also show if any steps taken to reduce high moisture are actually working. For instance, with a broken water pipe, you can all of a sudden have a very high moisture content in the crawl space. With the monitoring system you can make sure that over time the moisture content falls back to “healthy” levels. Moisture meters can be used in many different ways when working on restoring houses. This is only one of the many applications besides measuring flooring, furniture, siding, moldings, decks, etc. Essentially all materials which absorb and loose moisture should be checked.
Photo above shows another application of meter using built-in pins: the low value clearly shows that at this time there is no moisture in the area and repairs can be done instantly after moldy drywall is removed. The main advantage of Lignomat’s cable system is to be able to measure places that are hard to reach otherwise. I personally had a leak behind the sink and when the new cabinet was installed I put 1 pair of screws in the drywall to monitor behind the back wall of the cabinet. Every once in a while I am able to reassure myself that there is no more problems by quickly testing the site.

Dimensional Changes in Wood Floors

If it would not be for ugly deformations caused by cupping, bowing and gaping, nobody would worry about moisture and humidity. However, failed floors and customer complaints have made installers and clients more aware of moisture problems.

Most materials in the building envelope are hygroscopic. They contain a certain amount of moisture, however if there is too much or too little moisture in the air surrounding them, they will absorb or loose moisture. Problems in wood floors occur when there is an imbalance between humidity in the air and moisture in the wood . Wood is a hygroscopic material, which will absorb and loose moisture.

The finish on a floor plank will slow down moisture movement however it is not 100% tight. A wood floor will follow changes in moisture content and relative humidity. Stability of wood depends on 3 values: moisture content, relative humidity and temperature, with temperature having the least influence. (read more click here)

Corresponding values for stable conditions are listed in the EMC chart, one of the most important tables for any floor installer. The EMC chart shows values for 1.2% up to 24.3% wood moisture content for ambient humidity of 5%-95% at temperatures of 300 to 1000F.

For on-line EMC chart go to www.lignomatusa.com/EMC

If the moisture in wood changes, depending on species, wood orientation and exposure time then the wood shrinks and warps or buckles and cups.

For instance, the EMC chart shows, that wood with a moisture content of 10.1% is stable at 55% relative humidity and 700F. No cupping or shrinking will occur, as long as the relative humidity remains at 55%.

  1. If floor planks measuring a moisture content of 6% are exposed to air at 55% and 700F, the floor will pick up moisture until the relevant EMC value is reached at 10.1%. Wood species, coating and exposure time determine how much moisture is actually absorbed by the wood. However at 55% relative humidity, the floor will never pick up more moisture than 10.1%.
  2. If floor planks were installed at too high a moisture content (not confirmed at the time of installation), the floor planks will dry out and most probably cup during the months following the installation. At the time of the complaint, the floor planks are dry, which can be easily confirmed by a moisture meter. What cannot be verified at that time, is the initial moisture content, the culprit for the cupping. Since the moisture was not noted at the time of the installation, the installer is the most probably party deemed responsible for any repair work. Protect yourself from claims by using a moisture meter and thermo-hygrometer, when installing a floor.
  3. All is well, if a floor has been properly installed at 7% wood moisture and the relative humidity in the house stays at 40%. The floor will not suffer any cupping or gaping, as long as the relative humidity does not change. As time passes winter comes with very low relative humidity. RH inside a home can fall below 15%, unless a HVAC system is used. The drop in relative humidity will cause the wood to dry out, shrink and cup. According to the EMC chart, the wood moisture can drop down to 3.5%. Even though the wood may not reach the lowest possible value, as the wood dries out, little gaps become obvious and the home owner is complaining, trying to blame the installer. To protect themselves from claims, that are really not their fault, the installer should explain at the time the job is finished, that low relative humidity values occurring in the winter time can cause the floor planks to shrink and small gaps will occur. Those gaps will go away again during the summer, because of the increased humidity in the air. The only remedy is keeping the relative humidity between the recommended values of 30-50%.

There are meters available to measure moisture in wood and relative humidity in air with hi-precision relative humidity probes, such as the Ligno-DuoTec BW with Lignomat’s RH BluePeg probe. Wood moisture can be measured with the pinless meter function. As a bonus, the Ligno-DuoTec BW comes with dual-depth capabilities. This allows the installer to pin-point moisture conditions in two levels at ¼” and at ¾” deep. The meter can be equipped with the RH Probe for accurate relative humidity and temperature conditions. A data-logger is also an option as it keeps measurements for months or years of relative humidity and temperature in a home, independent of any climate control in the home.

Photo 1 shows a dual-depth, pinless moisture meter used to measuring an engineered floor. Note the depth has been set for ¼” deep to give reliable measurements of the hardwood top layer.

Photo 2 shows the same meter used to check the relative humidity in a gymnasium.

For questions call 800-227-2105

For on-line EMC chart go to www.lignomatusa.com/EMC

For more info on moisture meters go to www.lignomatusa.com

ASTM F2170 RH in-situ probe test

Please us link below to view Lignomat YouTube video.

The following video demonstrates Lignomat’s RH in-situ probe method. This follows the ASTM standard F2170. The new standard allows testing results after 24 hrs of acclimation.