Wood is a hygroscopic material, meaning it absorbs and releases moisture from the surrounding air. The moisture content of wood is expressed as a percentage of its oven-dry weight. When wood is freshly cut, it typically has a high moisture content, which can reach up to 50%. As wood dries, it loses moisture and its moisture content decreases. The equilibrium moisture content (EMC) of wood is the moisture content at which it is in balance with the surrounding air.
The preferred moisture content for treating wood depends on the type of treatment being performed. For example, wood that is being painted or stained should have a moisture content of 12-15%. This moisture content range allows the paint or stain to penetrate the wood and adhere properly. Wood that is being preserved should have a moisture content of less than 19%. This moisture content range helps to prevent the growth of mold and decay.
The moisture content of wood can be determined using a moisture meter. Moisture meters are available in a variety of types, including pin-type meters, which insert pins into the wood, and non-pin-type meters, which measure the moisture content of wood without damaging the surface.
The moisture content of wood can be controlled by using a variety of methods, including:
By controlling the moisture content of wood, it is possible to extend its lifespan and improve its performance.