Dry rot
Dry rot, wood decay caused by a fungus that feeds on wood, making it lighter, weaker, and more brittle. It is sometimes found in houses. Dry rot does not attack living trees. Despite its name, dry rot cannot live in dry wood, and a good way of avoiding it is to use well-seasoned timber and ensure that there is good ventilation around the structure.
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21st Century Webster's Family Encyclopedia21st Century Webster's Family Encyclopedia - Dream to Eijkman, Christiaan