Wood rot is the breaking down of wood by wood-rotting fungi. These fungi can only grow if the wood is damp for a prolonged period, usually above a wood moisture content of around 20%. The affected wood loses its strength, becomes soft and crumbly and changes colour. Dry wood that stays below 20% moisture does not rot: moisture is therefore the key factor.
Types of wood rot
- Brown rot — the fungus breaks down the cellulose; the wood turns brown and cracks into cubes (cubical). The notorious dry rot fungus (Serpula lacrymans) belongs to this group and can also spread through drier masonry
- White rot — also breaks down the lignin; the wood becomes lighter, fibrous and spongy
- Soft rot — surface decay in wood that is alternately wet and dry, for example in garden timber
Recognising and preventing
- Recognising — discolouration, a musty smell, wood that sags or that you can easily push a screwdriver into
- Vulnerable spots — window sills, wooden gutter edges, facade joinery, and cellar and crawl space beams
- Preventing — ensure good drainage and ventilation, keep wood clear of standing water, and maintain paint and stain coatings so that moisture cannot penetrate
- Repairing — remove affected wood down to sound wood; repair small spots with wood-rot hardener and epoxy filler, and replace larger sections
Always resolve the cause of the moisture first; otherwise the problem will return.
Related terms
- Wood
- Insects in wood
- Construction moisture
- Impregnating
- Ventilation
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