When an engineered floor is delivered to a jobsite, it should be inspected just like any other flooring material. For both engineered and solid wood floors, the inspection must include checking the moisture content of the floor planks. Additional moisture measurements should be taken and documented throughout the installation process. The final moisture readings should be recorded at the time the floor is signed off and handed over to the owner.
So, how can accurate moisture measurements be obtained in engineered wood flooring? First, a moisture meter is essential. Next, it is critical to select the correct setting on the meter. Moisture meters only provide accurate readings when calibrated properly for the material being measured.
Determining the correct setting is straightforward for solid wood floors, but it becomes more complex with engineered floors and other types of multi-layered flooring materials.
We have evaluated many engineered floors and recommended appropriate calibration settings to inspectors, installers, floor dealers and manufacturers.
Initially, the recommendation for engineered floors was to use the setting corresponding to the species of the wear layer when using Lignomat’s Dual-Depth pinless meter at the ¼-inch depth setting. However, after testing a wide variety of floors, we found that even engineered floors with identical wear-layer species can yield different readings. These differences depend on the thickness of the wear layer and the composition of the core and backing—even though the meter is only measuring ¼ of an inch deep.
For instance, we found that different engineered oak floors require different meter settings to obtain accurate readings. For example, the settings between the different floors ranged from 55 and 70. The variation between the two settings is 3% or even more. The discrepancies arise because engineered floors are built with different layers: the wear layer can range from less than 1mm to 6mm in thickness, and the core may consist of a single layer, up to 11 layers, or even high-density fiberboard with a backing layer.
The most reliable way to determine the appropriate meter setting is use sample boards that have been acclimated in a controlled environment with a known relative humidity. For example, at 45% relative humidity, the equilibrium moisture content (EMC) of the board should be approximately 7.7%.
If you want to find a setting for the test samples, which are at 7.7%, you can place the meter on the test sample and measure the moisture with a setting of 50. More than likely the moisture content is higher than 7.7%. Then, scroll through the meter settings starting at 53 and increase the setting. The moisture values indicated by the meter will decrease as the settings increase. Once the meter indicates approximately 7.7% you have found a setting that can be used to measure the same type of floor.
Grete Heimerdinger, vice president at Lignomat, has been heading the moisture meter division of the company since 1981, when the first pocket-size mini-Lignos were introduced. She graduated from the Technical University in Stuttgart, Germany, with a teaching degree in Mathematics and Physics. For more information, contact Lignomat at 800.227.2105 or email sales@lignomat.com.
