Wood is a natural, fibrous material, and it gains and/or loses moisture as changes occur in the temperature and humidity of the surrounding air. For example, lumber located in a cool humid climate would tend to have a higher moisture content than if the climate was warm and dry. This ability of wood to absorb or desorb moisture is important in wood design since moisture content affects the structural properties of wood.

Basic properties affected by moisture content include

  • Weight
  • Dimensions
  • Strength


          Moisture content for a given sample of wood is defined as the weight of water in wood expressed as a percentage of the weight of wood fibrous material (which is considered to be the oven dry weight of the sample).  In the lab, a specimen of wood is weighed then placed in an oven set at 100o C for 48 hours (as per ASTM Standard D2395-93).  The oven dry sample is then weighed. The moisture content is then calculated by the following equation:

Moisture content may range from 0% (oven dry wood) to greater than 200% (a living tree).


Last updated: 12 September, 2000