Although wood is naturally durable and strong, the effects of outdoor exposure on wood can destroy not only these physical properties, but its natural beauty as well. Moisture Water is one of wood's worst enemies. Whether in the form of vapor or liquid, water can cause shrinking and swelling, which can led to dimensional changes of the wood and degradation of the finish.
Water can also lead to decay or rot to occur in wood.
In general, it accelerates the weathering of wood exposed outdoors. Shrinking and Swelling Wood shrinks as it loses moisture and swells as it gains moisture. At this point, all the wood's water is bound within the cell wall. As moisture content changes above fiber saturation, the cell cavities take on or lose unbound water but the wood cell walls do not change dimensionally. Below the fiber saturation point, however, the wood will change dimension with changing moisture content.