What Is Kiln Drying? The Reasoning Behind Drying Wood

The Kiln Drying Process

When trees are felled and brought to a lumber mill, the first step is usually to debark and sort the logs by species, size or by end use. Logs destined for wood flooring, for example, are then sawn into rough boards of the required dimensions. These are often edged or trimmed for length before they are dried.

Drying can be done either by air or by kilns, which use circulating heated air to more rapidly remove the excess moisture from the wood. Each charge (or kiln load) is sorted by species and dimensions to optimize the process and to ensure that the final moisture content levels are even across the charge. After the wood has reached the correct moisture level for that species, it is sent through the planer and planed to its final dimensions, sorted to grade and shipped out. For wood flooring or other specific end products, the wood is typically shipped to a manufacturer for further planing, processing, and finishing. Mills and manufacturers alike invest time, money and training into their drying processes to provide optimal grade products at the correct moisture levels for their customers.

So if the wood leaves the kiln at the required moisture content level, the moisture content process is complete, right? It might seem feasible, but in reality, kiln drying is only the first step of a wood product’s life-long interaction with moisture. Kiln drying significantly reduces the moisture content of green lumber, but there’s more to be considered.