Wood is a porous material and
will absorb moisture from the air. Moisture is
attracted to the walls of the tubes that make up
the wood. Wood will only decay if it is in contact
with the ground or wetted by an external source
of moisture, such as rain seepage, plumbing
leaks, or condensation. Dry wood will never
decay. Also, the drier the wood, the less likely it
is to be attacked by most types of
woodinhabiting insects.