A.Paul Fisette, director of the Building Materials and Wood Technology program at the University of Massachusetts in Amherst, responds: Wood rots when it is attacked by rot fungi — living organisms that need four things to survive: food (wood), favorable temperatures (32°F to 100°F), water, and oxygen. If wood is rotting, you can stop the process by eliminating one of these four things.
Generally, the most effective approach is to keep the wood dry — below a moisture content of 22% (which corresponds to around 90% relative humidity). Once the wood is dry, the rot will go dormant, but it can reactivate when the moisture content again rises above 22%.
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