Moisture Content: Wednesday's Word(s) Of The Week

Several physical properties of lumber used to manufacture glulam are checked during the material grading process. One of these is moisture content: the percentage of a wood sample's weight that is water. This is most accurately measured by weighing a wood sample before and after completely drying it in an oven. That is impractical and undesirable to do for the material actually used in production, so various electronic meters are used which must be calibrated to the species of wood.

The moisture content of just cut trees is about 30%. At time of gluing, the moisture content is typically required to be 16% or less, nor should it vary by more than 5% average from board to board. In a building, a typical interior beam will be around 8%-12% moisture content, which can vary from season to season. 

Moisture content is important because wood will shrink and expand as it loses and gains moisture. With glulam we want to minimize the amount of dimensional change by starting with relatively dry material.

*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.