Wood rot is damage to wood caused by fungal colonies which settle on the wood and extend structures known as hypae into the substrate to take advantage of the nutrients and moisture in the wood. Around the world, wood rot is a very serious problem, and many people find themselves dealing with rotted wood at some point. It is also something which people routinely check for before they commit to purchasing real estate, as it can be expensive and time consuming to fix.
Any time wood is allowed to get moist and stay moist, wood rot can emerge. To prevent this, many lumber companies treat their wood so that it will resist moisture, often adding chemicals which harm fungi so that if the wood does get damp, fungi cannot settle on it. Proper ventilation of wooden structures is also critical, to keep fresh air blowing across the wood so that it stays dry, and wood-to-ground contact is generally to be avoided, as wood which sits on the soil will eventually attract fungi, causing rot.
This phenomenon is sometimes referred to as “dry rot,” despite the fact that the wood involved is often in fact quite damp. The term “dry rot” is a holdover from the time when people distinguished between wood rot in treated timber and wood rot in untreated timber. Treated timber was said to experience dry rot, while untreated and raw timber was simply rotting when it was colonized by fungi.
Classically, wood rot causes the wood to become crumbly, spongy, or stringy. Sometimes the outer layers remain intact, and the rot only becomes apparent when catastrophic failure appears. In some cases, the fungi in the wood may put out fruiting bodies, making the problem readily apparent. While it may be tempting to scrape off the fruiting bodies and call it a day, the presence of fungus on wood indicates the need to address the underlying wood rot.
Rotten wood generally needs to be removed. People can repair wood rot by taking out and replacing rotten wood, or by removing an area of rot and filling it with epoxy or another wood filler. Addressing the problem which led to the rot is also important, or the wood will simply start to rot all over again in the future. Some common problems which lead to wood rot include improperly installed foundations which permit wood-to-ground contact, leaking pipes which spill water inside walls and under floors, and leaky toilets, showers, and fridges.