When I grew up in Germany, we had what we called a “pitch pine” floor, which had gaps measuring about a quarter of an inch between the floor planks. Nowadays that would be totally unacceptable. I came to understand that the gaps developed because the planks were not dry when the floor was installed. The planks dried out after the installation had been finished. That is a flooring installer’s nightmare.
A perfect floor starts with a perfectly dry wood floor. But that is not all; the relationship between wood moisture and the environmental conditions of relative humidity and temperature is also important. The relationship between stable wood floor moisture content and relative humidity is documented in the standard EMC chart (see lignomatusa.com/emc/).
Every installer should have two instruments in his tool box—a moisture meter for wood and a thermo-hygrometer to measure relative humidity. Both instruments are used at all critical points during the installation.
First, a moisture meter is used to check the moisture content of the product when the packages are opened the first time. That would be the time to contact the flooring supplier if the moisture content is not approved.
Second, a moisture meter should be used to confirm the acclimation is achieved in accordance with the instructions from the flooring manufacturer. I have seen installers selecting a few boards, marking the location where the meter is placed and noting moisture content on the wood at different times during the acclimation process. The acclimation process is only successful when the relative humidity conditions are the same as when the floor is in service. (A data logger such as the Memo-Chip BL2 from Lignomat can be used to keep track of the relative humidity during acclimation. To make evaluating the measured conditions easily, the BL2 lists the EMC values.)
Third, measurements from a moisture meter and a thermo-hygrometer should be included in the final flooring installer’s report. This document should include several measurements from random locations and also from moisture-sensitive areas such as below windows, in entryways close to refrigerators or sinks. Be sure to document the name of moisture meter, measuring depth, measured value, thermo-hygrometer and temperature readings—as they are all important. If a photo is taken, it should show an easily identifiable landmark, measured value and, if possible, meter name and meter settings—plus the measuring depth and setting for wood species corrections.
At this time and with these measurements and the EMC chart, the installer can ensure the new owner of the floor that the floor will stay beautiful without cupping, checking or gapping if the relative humidity stays within the permissible moisture range. It could even be suggested that the owner buy a meter and a thermo-hygrometer and use these to watch out for unexpected moisture changes in his wood floors. In fact, Lignomat’s BL2 data logger can be set to sound an alarm if/when conditions get out of range.
For more information, visit lignomatusa.com/the-challenge-of-hardwood-floors/.
Grete Heimerdinger, vice president at Lignomat, has been heading the moisture meter division of Lignomat since 1981, when the first pocket-size mini-Lignos were introduced. Ever since then, she has been involved in updating and designing Lignomat’s moisture meters.
