Which type of wood decay is caused by a fungus spreading in damp conditions?

The correct choice relates to dry rot, which is a type of wood decay specifically caused by the Serpula lacrymans fungus. This fungus thrives in damp conditions and can spread rapidly through wood, causing significant structural damage. Dry rot is notable for its ability to infiltrate and weaken timber even in relatively low moisture environments, making it particularly insidious.

This decay occurs when wood moisture content exceeds a certain threshold, allowing the fungus to grow. The term "dry rot" might be misleading, as it can affect wood that is damp but appears dry externally. The fibrous mycelium of the fungus can extend throughout the wood and into masonry, leading to extensive damage if not addressed promptly.

In contrast, wet rot is also caused by fungi but typically arises in conditions where wood remains constantly wet, requiring a different treatment approach. Insect attack refers to damage caused by wood-boring insects, and wood shrinkage is a physical change that occurs due to changes in moisture content, rather than a decay process. Understanding these distinctions helps in proper identification and management of wood decay issues in design and construction.