The importance of proper moisture measurements

There should be no debate as to whether or not a moisture meter is needed. Expensive failures have taught everyone handling wood floors—from buyers to installers to inspectors—that the moisture content of hardwood floor is an important factor that decides the success or failure of a flooring installation. 

Wood is a hygroscopic material; it will gain moisture as long as there is moisture available to be absorbed—and it will lose moisture as long as the environment around the floor dries out the wood. Both conditions are followed by dimensional changes of the floor planks.

When absorbing moisture, wood can cup or crown. To the extent that this occurs depends on if the moisture is absorbed from the top or the bottom of the planks. When losing moisture, gaps could develop, resulting in cracks or surface checking. Usually, the surrounding air is the culprit for being too dry. 

Beyond the moisture content of the planks, it is also important to keep everything surrounding the wood floor in equilibrium with the moisture content of the wood floors. Wood will absorb moisture from a subfloor and the concrete slab underneath if they contain too much moisture. The relative humidity around the floor can also have an impact. Wood will react with the surrounding air and the floor moisture will change if humidity is too high or too low. 

Consider the temperature and RH in these conditions: 

• At 80°F and 75% relative humidity, wood will absorb moisture until 14% has been reached.
• At 70°F and 35% relative humidity, wood will keep a moisture content of 7%.
• At 70°F and 20% relative humidity, wood will lose moisture until 5% has been reached.

Benefits of pinless meters 

A pinless moisture meter can be of great help to pinpoint the present moisture condition. In a relatively short amount of time, wood flooring planks can be checked for moisture—all without making holes in the wood. When taking notes, it is important to write down the manufacturer and name of the meter, the calibration setting of the meter and the measuring depth and, of course, the moisture values. A photo can also be helpful showing the moisture value and the meter settings. The information will come in handy if any disputes about moisture conditions arise. 

If you have this information available and your customer complains about the moisture being too high, you can refer back to those notes and start to track the reasons for the change in moisture content. It may just be that your customer does not have a good moisture meter or does not know how to correct for the specific wood species. Without any previous measurements, you will have a hard time convincing the customer that the change in moisture content happened while the floor was under her/his care. 

When buying floors, do not wait too long before checking the moisture content in the shipment. Taking moisture measurements early on in the process covers both the buyer and the seller, and it will help to avoid potential problems and disputes.

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.