Whenever you purchase lumber for a woodworking or construction project, you can assume there’s going to be some level of moisture in the wood. However, it is important for those moisture levels to be kept in check. Knowing the moisture content of the wood is important, as it will give you an idea of whether or not the properties of that wood will change over time, and to what extent.
Here’s some information from a lumber yard in Houston about wood moisture content and what you should know.
An overview of moisture content in wood
How much moisture is acceptable in the wood you’re using depends primarily on what you’re using the wood for, the type of the wood, the thickness of the wood and the average relative humidity (RH) in the environment in which you’ll be using the wood. The standard guidelines for acceptable moisture level are going to be 6 percent to 9 percent for furniture, and 9 percent to 14 percent for construction.
People working with wood must also understand how wood interacts with moisture—otherwise the moisture content is just an empty number.
Wood is a hygroscopic material, meaning it will gain or lose moisture based on the RH of the air in which it sits. As humidity increases, the moisture content of the wood also increases, which causes the wood to expand. The inverse is also true—when humidity decreases, the moisture content also decreases, causing the wood to shrink. If the wood does not gain or lose moisture, then the wood has reached what is known as its equilibrium moisture content (EMC).
Many woodworking specialists believe wood should be dried down to a moisture content that is within two percentage points of the EMC of the location in which it will be used. This will make the wood more reliable and workable, and prevent any unforeseen problems due to shrinking or expanding in the wood.
This is why woodworkers generally like to store their wood for some time in the area they’ll be using it after they bring it home from the lumber yard—it allows the wood to acclimate to a new RH and environment. Say, for example, you bring home a piece of kiln-dried wood that has a moisture content of 8 percent, but decide to store it in a humid garage. You might find the wood absorbs another 6 percent or more of moisture. If you’re going to use the wood for an interior project, you’ll need to bring it inside and allow it to come into balance with the RH in the specific area you’ll be using it.
A failure to allow the wood to properly acclimate and get the necessary balance with the RH in its final location could result in cracking, warping and other problems after the construction project is complete.
For more information about why it’s so important to work with wood that has been properly dried, contact Houston Hardwoods Inc. or pay a visit to our lumber yard in Houston.