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

Newsletter: How to use a Reference Scale for Evaluating Concrete

 

May 2017,

Issue No. 20

Lignomat Product Video

Lignomat in situ probe method for ASTM F2170

(Watch Video)

Lignomat Ligno-Scanner SDM

(Watch Video)

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How to Use a Reference Scale When Analyzing a Concrete Slab

When placing a floor covering over concrete slabs a contractor must first evaluate the concrete to ensure proper acclimation has been met. We often use two different methods for evaluating moisture in materials a qualitative analysis and a quantitative analysis.

Qualitative vs Quantitative analysis. Often times with a moisture meter we describe the scale as a qualitative number or a quantitative number. A qualitative number is often referred to when using a reference scale. A reference scale commonly has a range from 0-100 and should be used in terms of more moisture or less moisture. We always tell our customers that this scale should only be used as a comparative reading. Thus one should take a reading in an area where there are no moisture problems and compare that reading to an unknown area where there could be a leak or more moisture. 

Another good application is when a floor installer is preparing to drill holes so he can set his RH probes to do moisture tests using ASTM F2170. The floor installer wants to set the RH probes so that he can get a good representation of the concrete slab. He uses the Ligno DuoTec BW in pinless mode, on setting 25, and starts scanning the floor. His average reading is between 35 and 45, however he has found a few spots that are reading a little higher in the 55 range. Since the floor installer wants to make sure the flooring he is installing stays as beautiful as the day he puts it in, he drills the holes where the moisture meter was reading 55. The meter has picked up more moisture in these areas however the number 55 is only a qualitative number it is not a percentage of moisture. The floor installer drills the holes and sets his sensor. 72 hours later he is ready to take some RH readings. He is getting readings that range from 65% -70%. This is a quantitative measurement taken using a RH% scale. From this we can analyze if the concrete slab is ready to have a floor covering installed. Using the manufactures specifications he can ensure that the concrete slab is ready for his floor covering. 

Floor installer taking a measurement on setting 25 in order to get a qualitative analysis of the concrete slab. Notice there is no unit of measurement on the reading.

The moisture in a slab sits 40% into the concrete slab. Only when a floor covering is placed on top of the slab will the moisture move to the surface and cause floor covering failure. Lignomat pinless moisture meters read up to 3/4″ into material, thus the information that you get from a pinless reading cannot alone determine if a concrete slab is ready for a floor covering. It is always recommended to use the ASTM F2170 test method for evaluating a concrete slab. 

www.lignomat.com  —  Email: sales@lignomat.com – 800-227-2105  —

Lignomat’s Unique Design for Taking Measurements Using ASTM F-2170

The RH BluePeg uses a single microchip, factory calibrated to NIST Standards. Each BluePeg comes with a NIST traceable certificate. The RH BluePeg probes comply with the latest ASTM F2170.

For the first year, Lignomat offers to check the probe calibration at no charge. For sensitive tests, the calibration of the removable probes could be checked after the test. We also sell a salt solution for the RH BluePeg probe which can be purchased for $49.00. The salt solution allows for easy calibration that can be done in-house over and over again.

Good Seal, Easier to Place Sleeves

Lignomat’s sleeves have feathered fins along their entire length, which provide an excellent seal. The lip of the sleeve covers the area around the concrete hole and provides another barrier for any air escaping. At the bottom of the sleeve is a movable cylinder, which places the RH probe every time as required by the ASTM F2170. Standard sleeves require no cutting. 3″ long sleeves are available. We also have top extenders that can be used when measuring gyp-crete.

Better Sealing, Flatter Caps

 Lignomat’s caps come with an o-ring to absolutely seal the sleeves. The caps are flat and do not interfere with any traffic around the test area. We supply red caps to easily spot the sleeve with a RH BluePeg sensor.

Fast Connection

A fail-proof, easy-connect 35 mm stereo plug is used to connect RH probes. No twisting, turning or setting-up an instrument for readings. No pin arrangements need to be fitted.

Most Accurate Testing

Our meter instantly shows the RH and temperature values. The resolution on Lignomat’s meter is 0.1%. No guessing or rounding up.

 

 

Newsletter: How to Make Sure Your Moisture Meter is Working Correctly

 

November 2016,

Issue No. 19

Interesting Websites

Calibration of Handheld Moisture Meters. 9 Wood:

(read more)

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How to make sure your moisture meter is working correctly.

Every floor installer and inspector should have a meter to check the moisture in wood floors. Having a moisture meter and knowing how to use it is not all there is to know. It is also important to know how to check calibration and function of the meter to avoid false measurements.

Floor installers should measure the moisture content upon delivery, before and after acclimation and when the floor has been installed.

Recently I had a phone call from a customer asking me, why two meters he is using on the same floor read differently. He said one meter consistently reads around 6%, whereas the other meter from a different manufacturer read consistently no values lower than 8%. We finally figured out the reason for the discrepancy by checking the default readings for both meters. (Default reading is the value a meter indicates, when the read button is depressed with nothing connected and pins pointing into the air.)

The default reading for one meter was 6% the other meter read 8% even though the pins were not touching any wood. A moisture meter will never read any lower than the default reading, which means the meter with the 8% default reading will never be able to indicate any moisture content below 8%, even when measuring drier wood.

Since the moisture meter user may not be aware of any malfunctioning of the meter, it is advisable to check the basic functions of a pin and pinless meter before and after each test series. In addition, the calibration of moisture meters can be checked with calibration test blocks available from the moisture meter manufacturers.  These external check blocks are essential for a valid check procedure. Moisture meters often have internal calibration checks, but those checks do usually not include the connection to the measuring plates for pinless meters or the connection to the pins, cables or hand probes for pin meters.

Basic function check for pin meters:

When the on-off switch or read button is depressed by hand without touching the pins, the lowest moisture value for the chosen wood species setting should be displayed (default reading). This test indicates there is no short within the circuitry. Meters may also show higher values if the area between the 2 pins is contaminated or has condensation.

This meter from Lignomat shows the lowest value (default reading for wood group setting #3) with the decimal point blinking. On-off switch between the pins is depressed, but fingers are not touching the pins.

When the on-off switch or read button is depressed and both pins (integral pins on the meter or pins of the external probe) are touched at the same time with two fingers, at least 12% should be indicated. Continuity test indicates that the connection from pins to circuit board to display is working.

Calibration check:

Last, the calibration can be checked with the pin test block. The pin check block consists of one or two resistors which produce a certain moisture value when pins are touching the contact points of the calibration check block. 

Only an external check block can confirm, that probe, cable and meter are functioning properly. Measurements are supposed to be within +/-1% of 12% for this calibration check block.

Basic function check for pinless meters.

When the on-off switch or read button is depressed and nothing is touching the measuring plates on the back of the meter, the lowest moisture value for the chosen wood group is displayed (default reading).

Hold meter in the air to make sure no material is touching the measuring plates and the lowest possible value appears on the screen with “Min”. 

For the continuity test, place the pinless meter on your forearm and depress the read key, a high moisture value should be indicated. An additional meter check can be performed by measuring a realm of paper. If the paper test is done repeatedly with the same setting, the indicated value should not vary significantly over the course of a year. This can be used to check consistency and accuracy of the calibration over time.

 Last, the calibration can be confirmed with the calibration check block. The check block for pinless meter is usually a material plate which produces a defined reading when the meter is lightly pressed against the surface.

Always press down slightly on the meter when taking measurements and when checking the calibration with a calibration test block. 

After checking the meter with the above described methods, you think you are ready to take measurements. Stop. A very important next step is to set the meter for the correct wood species. Find out about the wood species.  Find out if it is an engineered floor and what the hardwood species of the top layer is, set the dual-depth meter for that species and the ¼” measuring depth. Now you are ready to start a test series.

Last, your moisture measuring report should include place, date, moisture meter brand and instrument name, pin or pinless, wood species setting and measuring depth, location where the reading was taken and indicated moisture value in percent. A photo of the meter while taking readings is always helpful.

What if all of the above has been followed, but accidently the wrong species setting has been used for the measurements. If you cannot go back to take the readings again, ask the meter manufacturer, if they can tell you what the readings would have been with the correct setting.

www.lignomat.com  —  Email: sales@lignomat.com – 800-227-2105  — Grete Heimerdinger

Product Manager at Lignomat.

 

Newsletter: Storing and Acclimating Your Lumber

 

August 2016,

Issue No. 18

AT A GLANCE

*Storing and Acclimateing Your Lumber

* Moisture in Concrete: Free and Bound Moisture

Interesting Websites

Concrete Floors and Moisture

(read more)

Scientific article about different methods to measure moisture in concrete. Great information about the different types of water in concrete.

(read more)

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Storing and Acclimating Your Lumber

Many woodworkers end up collecting and storing all different types of wood whether its leftovers from a previous project , or wood for a project that will be happening down the road. It usually ends up in an old shed or the side of the workshop and of course preferably in a climate controlled room. Where ever you may be storing wood it is important to understand how the climate the wood is in affects the usability of the wood.

 

If dry wood is stored in a damp place the wood will pick up moisture and expand until equilibrium with the surrounding air has been reached. If the wood is stored in a dry area the wood will lose moisture and shrink until equilibrium has been reached. For corresponding values check the EMC chart.

 

Proper acclimation of your wood before starting a project will minimize moisture problems when the woodwork is done and brought into the home. Nothing is more frustrating than making a nice dresser and bringing it into the home only to have it shrink and cause loose joints. An easy recommendation that we always provide our customers is to take a moisture meter and measure a table or some other woodwork in the home. Once you have established what the wood has acclimated to in the home then you have a MC% of what you want your wood that you are working with to be.

Moisture in Concrete, Free vs Bound Moisture

Water in concrete is presented in three states: as free water held by capillarity, as absorbed water held by surfaces forces and as bound water held chemically. The ideal method of moisture measurement should quantify amounts of these three states but this is a difficult task because moisture in concrete is not uniformly distributed, and moisture distribution varies with the exposure time (Li Chunqiu 2008). Temperature, wind speed and environmental relative humidity are variables that must be considered at the moment of this measurement as well.

 

Using a pin moisture meter or a pinless moisture meter Is not a good method for analyzing moisture in a concrete slab. These types of meters are not able to pick up the different types of water in concrete. The meter will measure all of the water in the slab not just the free water.

The free water is what is going to affect the vapor emissions that will cause floor covering failure.

 

Measuring the moisture of a concrete floor is very hard because of the nature of concrete. The floor covering industry is always evolving and trying to incorporate a more accurate and efficient method for evaluating moisture in a concrete slab. 10 years ago people were only doing the calcium chloride test when analyzing moisture in concrete. Today many manufactures and people in the floor covering industry have moved to using the RH in-situ probe method following ASTM F2170 standards. Lignomat has developed a system for measuring concrete following the ASTM F2170 guidelines. Please call if you are interested in purchasing. If you would like a more detailed video of how the system works please visit link below.

 

https://youtu.be/UnyRz6XFTqs

Li Chunqiu, L. K. ( 2008). “Numerical analysis of moisture influential depht in concrete during drying wetting cycles.” Tshingua Science and Technology Vol 13, N°5: 696-701.

 

Newsletter March 2016: Case Study Floor Covering Failure

 

March 2016,

Issue No. 17

AT A GLANCE

*Case Study: Customer Calls with Floor Covering Failure

* Why is Wood Cupping and Shrinking?

Interesting Websites

Popular Woodworking Magazine: Moisture Meters

(see more)

Understanding, Preventing, Detecting and Correcting Moisture in Concrete Floors

(read more)

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Case Study: Customer

Calls with Floor Covering

Failure

We recently had a customer call us with a problem. He was called onto a site where the floor had cupped and boards were twisted. He wrote us that he inspected a wood floor, ¾ x 5 inch, stapled down, upstairs over plywood.  Consumer told him the species was Teak.  The ¼ and ¾ depth readings were done with a SDMspecies setting 55. 

While writing the report, he called and found out from the floor reatiler that the species was Timbauba.  The product name for the consumer was Golden Teak.  So he do not know how to adjust the meter readings.  

Location            1/4″ depth        3/4″ depth           

     

Hall                        12.4                12.4                    

Hall                       10.9               11.1          

Bedroom front      10.1                10.4              

Front closet          11.9               12.3               

Hall bedroom        11.1               11.3               

Master                   10.2               10.7               

Shelf                      12.8              12.8            

Shelf                      11.4              11.6

Pieces of wood sent in by customer to be evaluated. The wood as shown above was warped. 

Grete Heimerdinger’s response – VP Lignomat

here is a web-site which has information about Timbauba http://www.fpl.fs.fed.us/documnts/TechSheets/Chudnoff/TropAmerican/htmlDocs_tropamerican/Enterolobiumschomburgkii.html

The specific gravity for Timbauba is very different from 55, that is why those measurements came out so different. The low Lignometer K readings indicate that the meter was giving default readings, which means the resistance in the wood is so high , that the meter cannot measure the wood.

The SDM readings were corrected for setting number 55. To see the difference in readings between 55 and 84, I took a piece of White Oak and measured the moisture on setting number 55. The readings were about 11.1, 11.0.Then I changed the settings to number 84 and took readings again of the same White Oak piece in the same location and the measurements showed 6.9 and 7.0. Changing the setting from 55 to 84 will reduce the measured values by about 4%. I hope this information helps. Let me know, if you have any more questions.

 Grete 

When taking measurements of a piece of wood it is crucial to have the proper calibration for the species of wood to be tested.

When using a pinless moisture meter the specific gravity is the calibration factor. With Lignomat pinless moisture meters you simply put the specific gravity into the meter. For example: Specific Gravity of Timbauba is 0.84 so the Ligno-Scanner moisture meter should be set to 84.

The calibration for a pin type moisture meter is a little more complicated. Lignomat performs an oven dry test to find the appropriate calibration for the wood. When you have a moisture meter with 2 wood group settings all woods are put into those two settings depending on the oven dry results. When you have a moisture meter such as the Lignometer K which has 150 different wood groups there is a much finer calibration so you will get a more accurate reading depending on the wood species.

Lignomat offers free oven dry testing for any wood that we have not tested in the past.

For this case study we did not have a setting for Timbauba so the inspector was asked to send in a few pieces of wood no more than 6″ long so that we could establish the proper Lignometer K setting for his wood. 

After the oven test the results were as follows:

Warped piece of wood measured 8%

Unwarped piece measured 8.7%

This obviously shows that the readings that were taken with the wrong settings were inaccurate. After the oven dry test is done a calibration for the moisture meter is established. 

Nobody needs to wonder why the warped wood tested with such normal moisture contents. Lets assume the wood floor was delivered, not tested, and installed at a higher moisture content than 6-9%. As the wood dried out, it warped and then when tested it showed the right low MC.

Make sure to give Lignomat a call if you are having problems finding the correct wood species settings. We can help.

800-227-2105

sales@lignomat.com

Why is Wood Shrinking and Cupping?

Wood movement occurs, when the moisture in wood changes. Then, floors are cupping, table tops delaminating, veneer is checking and boards are warping.
No shrinking and warping will occur, when an equilibrium with the surrounding air has been reached, which means wood is not losing or absorbing any moisture. 
The EMC chart below lists stable wood moisture 
values between 2.3% and 24.3% for ambient conditions of 10-95% RH at temperatures of 30-1000F. According to the chart, wood at 10.1% will not shrink or warp, if the relative humidity remains at 55%.
Besides listing stable conditions, the EMC chart 
allows predictions and explanations:
For instance, if dry wood with a moisture content 
of 6% is exposed to 55% relative humidity at 700F, 
the wood will pick up moisture until 10.1% has been reached. Wood species, coating and exposure time determine how much moisture will actually be absorbed. However, at 55% relative humidity, wood 
can never pick up more moisture than 10.1%. 
An all important pair of tools: Hygrometer and wood moisture meter
No more surprises!
Measure and compare wood moisture and relative humidity with the EMC chart to predict, if wood is stable or will loose or gain moisture.