Dry rot fungus

Serpula lacrymans, commonly known as the dry rot fungus, is the most notorious wood-destroying organism affecting buildings. It belongs to the Basidiomycota phylum and is responsible for causing extensive brown rot, which compromises the structural integrity of timber by breaking down cellulose and leaving the wood brittle and fractured.

This fungus predominantly infests coniferous wood, but it can also attack various types of hardwood. It thrives in domestic buildings, particularly affecting floor joists, skirting boards, door frames, and wooden beams hidden behind plaster or panelling, often remaining undetected until significant damage has occurred.

Key symptoms include the growth of fluffy, white, cotton-like mycelium, which often develops into large, greyish sheets with yellow or purple patches. The fungus produces fleshy, pancake-shaped fruiting bodies that release masses of rusty-red spores. In active stages, it can also exude droplets of water, leading to its specific name.

The fungus requires specific environmental conditions to flourish, primarily high humidity levels (above 20-30% moisture content in wood) and stagnant air. It is uniquely capable of transporting moisture through its specialized strands called rhizomorphs, allowing it to spread across non-nutritive surfaces like bricks or mortar to infect distant timber.

Effective control measures require a systematic approach:

• Eliminate the moisture source, such as plumbing leaks or rising damp.
• Increase ventilation to ensure timber remains dry.
• Remove all rotted timber, including a safety margin of healthy wood.
• Apply professional-grade fungicidal treatments to the surrounding masonry and remaining wood.

Prevention is the best strategy against Serpula lacrymans. Maintaining a dry building envelope, ensuring proper insulation of foundations, and avoiding direct contact between wood and soil are essential practices to mitigate the risk of infestation and preserve structural timber for years to come.