Working with wood flooring materials isn’t an easy job. When high-quality wood is installed well, it can be one of the most beautiful and long-lasting flooring materials on the market.
However, there is one factor that can complicate a wood flooring installation job that many clients don’t know about: moisture. Typically, it’s assumed that any flooring materials are already properly acclimated and free of excess moisture, but such assumptions can be dangerous.
If the moisture content of wood flooring isn’t right, then it can warp, buckle, or even delaminate, causing significant damage and ruining the aesthetic value of the flooring. To make sure that the moisture content of wood flooring is in the right range, many professionals use flooring moisture meters to test their wood flooring materials and subfloors prior to installation.
But, what is the ideal moisture content for wood flooring?
The answer to this can change depending on the temperature and ambient moisture conditions of the installation site.
How Humidity Influences Ideal Wood Moisture
Wood is a hygroscopic material, constantly absorbing and giving off moisture until it reaches an equilibrium moisture content with its surroundings.
In short, the more humidity that is present in the air, the more moisture wood building materials, such as flooring, will absorb. This has a direct effect on how much wood flooring will expand after installation. As wood absorbs water, it will expand across the grain, which can cause it to swell, warp, and buckle.
By contrast, environments with less humidity tend to make wood lose moisture. Here, the wood will shrink across the grain, which can cause the wood to warp and crack.
For all intents and purposes, the ideal moisture of flooring wood will be the moisture content at which the wood reaches equilibrium with the installation environment. At this equilibrium moisture content (EMC), wood will stop absorbing or shedding moisture, which prevents some of the physical problems that can occur in wood flooring.
Temperature and Ideal Moisture for Wood
The temperature of the installation environment can affect not only the rate of moisture absorption/depletion for wood, it can influence the relative humidity of the air (RH values are expressed as a percentage of how much moisture is in the air compared to how much it could hold at that temperature).
Basically, as the air in an area gets warmer, it can hold more humidity before letting water condense. As the air gets colder, the amount of humidity it takes to saturate the air drops. So, if you have two rooms with the same total amount of water in the air, but at different temperatures, the warmer room would register as having a lower RH value than the cooler room.
Because of this, the temperature can have an effect on the ideal moisture content of flooring materials.
Ensuring Wood Flooring Is at Its Ideal Moisture Content
Before you can ensure that your wood flooring is at an ideal moisture content, it’s important to check the relative humidity of the installation site and compare that to the %MC of your wood materials. Here, using a thermo-hygrometer to check temperature and humidity can be invaluable.
In most cases, your installation will probably in a zone with RH values between 40% and 45%. If the temperature of the building is between 75 and 85 degrees Fahrenheit, the equilibrium moisture content of your wood should be between 7% and 8%.
However, in some coastal areas, the average RH is in the 58% to 63% range. In these areas, your target RH is probably going to be closer to 11% in most wood materials for an indoor environment.
How do you know if your flooring is at the ideal moisture content for wood in your installation site? By using a moisture meter for wood flooring! Wood flooring meters can be used to quickly measure the moisture content of wood and come in two varieties:
- Pin Meters use the principle of electrical resistance to measure moisture. By passing a current through the wood between the pins of the meter, the resistance to the current can be measured and used to determine how wet the wood is because water is a conductor and wood is an insulator. More water equals less resistance.
- Pinless Meters use an electromagnetic frequency to "scan" a piece of wood for the presence of water. By checking distortions in the wave, the meter can establish how much water is present in the scanned area.
To ensure that your wood is at the right moisture content for use, check the RH value of the installation site with a thermo-hygrometer, and then check the %MC of your wood flooring with a flooring moisture meter. Doing so can help ensure that your wood floors won’t warp or buckle after the installation is complete.