What is Wet Rot?

Wet rot is a form of fungal decay that occurs when timber is exposed to prolonged moisture, typically in areas with poor ventilation or water ingress. Unlike dry rot, wet rot remains confined to the damp area and does not spread to dry timber. However, it can still cause significant damage if left untreated, weakening the wood and compromising a building’s structural integrity.

Key Features of Wet Rot:

Cause:

  • Dry rot is caused by a fungus called Serpula lacrymans. It thrives in damp, poorly ventilated conditions and feeds on the cellulose and hemicellulose in wood.

Conditions for Growth:

  • Moisture: Typically, timber with a moisture content of 20% or higher.

  • Poor Ventilation: Areas with little airflow, such as basements, underfloor spaces, and behind walls.

  • Temperature: Thrives between 22°C and 27°C but can survive in cooler conditions.

Appearance:

  • Early Stage: Wood becomes discolored and brittle.

  • Cracks or cuboidal patterns may appear on the surface of the timber.

  • Advanced Stage: A cotton-like white or grey fungal growth may appear on or near the affected timber.

  • Rusty-red or orange spore dust can collect on nearby surfaces.

  • Fruiting bodies resembling large, flat mushrooms may develop, often with a strong, musty odor.

How It Spreads:

  • Dry rot spreads through microscopic spores that travel through the air.

  • The fungus can extend across non-wood materials (e.g., brick, plaster) in search of new wood to infest.

Signs of Dry Rot:

  • Weak, crumbling timber that breaks easily.

  • Distinctive cracking pattern in the wood (cuboidal cracking).

  • Damp, musty, or earthy smell.

  • The presence of fungal growth (white, fluffy mycelium or mushroom-like fruiting bodies).

  • Rust-colored spore dust near affected areas.

Prevention:

  • Control Moisture: Repair leaks in roofs, walls, or plumbing. Ensure good drainage around the property. Use proper ventilation in areas like basements and attics.

  • Maintain Timber: Keep wood dry and well-sealed with protective treatments. Avoid direct contact between timber and damp surfaces, such as soil or concrete.

Treatment:

  • Remove the Source of Moisture: Fix leaks or other causes of dampness. Improve ventilation and reduce humidity in affected areas.

  • Remove Affected Timber: Severely decayed wood should be removed and replaced with treated timber.

  • Apply Fungicidal Treatment: Use specialized fungicides to treat the surrounding areas and remaining wood.

  • Monitor and Maintain: Regularly inspect the property for signs of damp or fungal growth.

Key Difference from Dry Rot:

  • Wet rot is localized to areas of high moisture and does not spread into dry areas, unlike dry rot, which can travel across non-timber materials in search of new wood to infest.

Professional Help:

If wet rot is suspected, consulting a specialist is advisable. They can assess the damage, determine the underlying cause, and provide tailored solutions to repair and prevent further decay.