Moisture affects wood in several ways. As air becomes damper, the moisture content of wood exposed to the air changes. Due to these changes in wood moisture content, the wood’s dimensions, strength properties and potential for fungal activity change. The following chart summarizes the properties of wood as a function of moisture content of the air. This chart represents a generic species of wood: A particular species or sample of wood may exhibit different property changes, but the pattern is similar.

One of the more visible changes that occur in wood in a home occur with hardwood floors. See examples of problems encountered with hardwood floors as a result of MAD wood relationships.