To find rot in a used wood fence, carefully examine its posts at the ground level and anywhere the wood comes into contact with vegetation or moisture. In addition to wet rot, be on the lookout for dry rot that occurs as the wood loses the protective oil covering its surface, making it brittle.
Certain types of wood are more susceptible to rot than others. For example, hard woods such as cedar, oak, redwood and cypress are resistant to both forms of rot and resist environmental factors well as a result.
Another way to determine whether a particular wood is susceptible to rot is by examining the certification label or stamp for the wood. A timber company that supplies wood or pressure treats it for certain uses typically assigns the wood a rating. For instance, an above-ground use rating implies that the wood is subject to rot if used for fencing.
When checking a fence for the presence of rot, be sure to check for debris accumulation on the fence. Leaves and other organic matter, once left to accumulate on or under the fence, contribute to rot and invite insect infestations. Debris that accumulates in crevices and crack in the wood of the fence represent a serious risk of rot.