Defect 4 – Dry Rot

The first three articles of this series looked at the potentially devastating effects of damp in its various forms. We move now from the very wet, to what you might presume to be the very dry – dry rot.

Interestingly though, dry rot belies its name. Conditions of at least 20% moisture are required for the dry rot fungus (Serpula lacrymans) to form – which means that, somewhat ironically, timber must be damp for dry rot to become an issue.

When it does form, the results can be devastating to a property. Unlike wet rot, which largely sticks to the timbers, dry rot has the capability to spread to other building materials – giving outbreaks the potential to spread far within the building.

If you notice any of the following, you may need to take remedial action:

  • A musty, damp odour.
  • Wood shrinking, darkening and cracking
  • Depending on the humidity:
    • Cottonwool-like mycelium develops under humid conditions and so called ‘teardrops’ may form on it.
    • A mushroom coloured skin frequently tinged with patches of lilac and yellow often develops under less humid conditions.
  • Fruiting bodies are a soft, fleshy pancake or bracket with an orange-ochre surface and wide pores.
  • Rust red coloured spore dust frequently seen around fruiting bodies.

The key to addressing dry rot issues lies in removing the dampness which provided the necessary environment in the first place.

The root cause can be an appliance issue, like a leaking shower, or it can be one of the major forms of damp – rising, ingress or condensation . If that source of moisture can be removed, then the wood can dry out and the dry rot be brought under control.

The solution should not end at this stage, however. Affected timber should be removed and replaced with pre-treated timbers. Other compromised building materials should also be replaced where practical and any elements that remain should be treated with a fungicide.

If areas beyond the timbers have been affected, it may become necessary for masonry sterilisation and / or physical containment.

Ultimately, dry rot can be very damaging to a structure and, if left unaddressed, extremely expensive to rectify. If you have any concerns, contact your local surveyor or a dry-rot specialist to offer an expert opinion.

*Back to June 2016 Newsletter*

©     SJ