Treating Timber Rot

Treating Timber Rot in Buildings

Timber Rot in buildings is a decay process caused by moisture and fungal growth, which can affect structural timbers like joists. It is categorised into two types: dry rot (Serpula lacrymans) and wet rot. Dry rot is particularly destructive, able to traverse dry masonry to infect timber. Wet rot, conversely, is confined to damp timber.

Identification: To identify rot, look for:

• Timber discoloration.
• Musty smell.
• Soft, spongy wood.
• Fungal growth.

Dry Rot Identification:

• Deep wood cracks.
• Silky, mushroom-coloured skin.
• Field mushroom-like smell.
• Rust-red spores near the outbreak.

Wet Rot Identification:

• Any rot other than dry rot – see identification above
• White fungus.
• Darkened, softened wood.
• Damp, musty odour.

Treatment Process:

1. Source Identification:
   • Rectify the moisture source to prevent ongoing rot.
2. Timber Strength Assessment:
   • Use a screwdriver to check timber strength.
   • Normal load areas: at least half the timber intact.
   • High load or thoroughfare areas: two-thirds intact.
3. Removal of Affected Timber:
   • Replace decayed timber with pre-treated timber to reduce risk of future rot.
   • Ensure new timber doesn’t contact damp masonry.
   • Use a plastic membrane for timber ends.
   • Strengthen timber affected by wet rot with supporting timber.
4. Primary Treatment:
   • Remove water and vapour sources; essential for rot prevention.
5. Drying Out:
   • Use dehumidifiers, fans, or mechanical ventilation or improved sub-floor air bricks.
6. Preventative Measures:
   • Identify water sources, use sump pumps, improve ventilation, and conduct regular checks.
7. Fungicidal Treatment:
   • Fungicide, such as sodium octoborate is not a substitute for removing water sources.
   • Apply fungicide to affected and adjacent timber.

Note: Consult a professional damp surveyor for accurate diagnosis and treatment. Misidentification can lead to ineffective treatment and further damage.