The moisture content of lumber plays a significant role in its durability and performance. Lumber that is too wet or too dry can be prone to warping, splitting, and other issues that can affect its strength and stability. When people set out to build their dream home they intend on being able to enjoy the finishes for many years to come. The perceived quality of service and material will often be attributed to these factors.
When lumber is freshly cut, it contains a high moisture content, typically around 50%. This moisture is known as "green" moisture, and it is present in the cells of the wood. In order to make the lumber suitable for use in construction and other applications, it must be dried to a specific moisture content level.
The most common way to dry lumber for custom homes is by kiln drying, which involves placing the lumber in a controlled environment, such as a kiln, and using heat and airflow to remove the moisture. Kiln drying is a common method used by lumber mills to produce dried, or "kiln-dried," lumber that is ready for use.
The moisture content of kiln-dried lumber is typically around 8-12% ( some lumber providers supply up to 13% - 15%), depending on the species of wood and the intended use of the lumber. This moisture content is considered to be "equilibrium moisture content," or EMC, which means that the lumber is in balance with the relative humidity (RH) of its environment.
Lumber that is too wet or too dry can be prone to issues such as warping and splitting. Lumber that is too wet will absorb moisture from the air, causing it to swell and potentially warp. This can cause cupping on ceilings within kitchens of custom homes. On the other hand, lumber that is too dry will lose moisture to the air, causing it to shrink and potentially crack or split. On ceilings and soffits this can attribute to gapping as well.
Maintaining the proper moisture content in lumber is important for its durability and performance. Lumber with an EMC that is in balance with the RH of its environment will be less prone to issues such as warping and splitting, and will be more stable and durable over time. When it comes to the build out of high end custom homes, this longevity can make a huge impact on the long-term success of the project.