Dry rot is caused by certain fungi that attack timber when it becomes damp, with a moisture content above about 20%. The spores of dry rot fungi are airborne and germinate when they land on damp, untreated wood. The fungi then consume the wood, which weakens it structurally. Moisture usually gets into the timber due to various building faults, such as leaking gutters, poor ventilation, broken roof tiles, leaking pipes, rising damp, or condensation. The fungi thrive in moist, poorly ventilated, and dark environments, and the infestation can spread through timber and even masonry, causing severe structural damage if untreated.

Causes of Dry Rot in Detail

• Damp timber with moisture content above 20% is essential for dry rot development.
• Moisture sources include leaking roofs, gutters, pipes, rising damp, penetrating damp, and condensation.
• Poor ventilation allows humid air to linger, creating a favorable environment for fungal growth.
• Untreated timber, especially in older buildings, is particularly susceptible.
• Missing or broken damp proof courses can cause rising damp, increasing risk.
• The spread of dry rot fungi involves the growth of fungal hyphae and mycelium, which extract moisture from wood, further weakening it.

Summary

Dry rot is caused by fungi infecting wood that has become damp due to water ingress or condensation. It requires a suitable moisture level and poor ventilation to thrive. Addressing the source of moisture and using treated timber helps prevent dry rot. If dry rot occurs, it poses a serious threat to building stability.