Timber: Dry Rot and Wet Rot

All fungal decay occurs when timber becomes wet for a prolonged period of time.

What is the difference between wet rot, and dry rot? 

Wet rot is more common and tends to be confined to the area where timber has become and remains wet. 

Contrary to what the name suggests, dry rot requires considerably more moisture for an outbreak to begin and tends to be more serious, requiring extensive specialist treatment. It can also travel through masonry, plaster etc. to find another food source. If dry rot is not treat correctly, it will almost certainly return. 

How to identify dry rot

Dry rot can spread through timber, masonry and wall plaster. It tends to shy away from light, often occurring in dark areas such as under floors and behind panelling, so it can go undetected for long periods of time.

Tell tale signs of dry rot include:

  • Mycelium growth: this occurs as a white or grey cotton wool like substance which can spread extensively.
  • Fruiting body (sporophore): ‘pizza-like’ in appearance, these can appear in an array of shapes and sizes and most are a deep rusty red colour, with white outer parts.
  • Cuboid shaped cracks in the affected timber where the wood has dried out and shrunk

An example of a Dry Rot fruiting body underneath a front door

How to treat dry rot

This specialist treatment involves removing all decayed timber, stripping wall plaster, and sterilising masonry. If the growth is not completely removed, it can reoccur. Affected timbers cannot be left in place unless under very extreme circumstances, such as in some historical buildings or structural timbers.

How to identify wet rot

Wet rot is usually confined to an area where timber has become and remains wet. Indicators of wet rot include:

  • Timber feeling soft or spongey
  • Timber with a tendency to crack or crumble
  • Skirting boards, window and door frames shrinking and leaving a paint veneer

Wet rot in a garage roof timber

There are many types of wet rot, and some, such as Coniophora puteana, can be easily mistaken for dry rot. The correct identification of the type of rot is absolutely essential.

How to treat wet rot

Removing the source of moisture and drying out the timbers will cause any attack to cease. Structurally damaged timbers may need to be replaced and timbers at risk of further decay may require treatment, such as the application of a preservative.

If you suspect your property may be suffering from dry or wet rot, contact our team of experts so we can arrange to come out and diagnose the problem and suggest a course of action.

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