At what moisture content percentage does wood rot typically begin to occur?

Wood rot typically begins to occur at a moisture content of approximately 20%. At this moisture level, the wood becomes sufficiently damp to support the growth of fungi, which are the primary agents responsible for wood decay. When wood fibers absorb moisture, they can create an environment conducive to fungal activity, leading to structural weakening over time.

Moisture content above this level allows fungi to thrive, and while some may argue that decay can start even slightly lower, 20% is widely recognized as the threshold where the likelihood of rot significantly increases. Furthermore, maintaining wood moisture levels below this percentage is crucial in preventing rot and extending the life of wooden materials in construction and other applications. Keeping moisture levels below this point mitigates the risk of decay and associated damage, highlighting the importance of monitoring and managing moisture in wood products.