Surveyor’s Guide to: Dry Rot in the home

Plumbing at Dunster Castle, Somerset

Dry rot is something of a misnomer and you may easily be mistaken in thinking that it will only thrive in dry conditions, but ironically Serpula lacrymans, to give the fungus its proper name, requires the presence of moisture.

An environment of at least 20% moisture is required for the fungus to form. So, for timber to suffer dry rot it must be located in damp conditions.

The results of untreated fungal growth within a property can be truly devastating. Unlike wet rot, which largely sticks to the timbers, dry rot has the ability to spread to other building materials, and there is the potential for further outbreaks to occur far within the property.

A musty, damp smell is often an early indication of its presence, and immediate remedial action will be required if you notice any of these tell tale signs:

– Wood shrinking, darkening and cracking
– Under high humidity conditions, cotton wool-like mycelium develop and so called ‘teardrops’ may form on it.
– In less humid conditions, a mushroom-coloured skin frequently tinged with patches of lilac and yellow often develops.
-Fruiting bodies are a soft, fleshy pancake or bracket with an orange-ochre surface and wide pores.
– Rusty-red coloured spore dust frequently seen around fruiting bodies.

The key to addressing dry rot issues lies in removing the source of the dampness that provided the necessary environment for the fungus to thrive in the first place.

The damp can be the result of one or more of the major forms of damp: rising, ingress, condensation or defective plumbing. The root cause can sometimes be as simple as an appliance issue, such as a leaking shower or waste pipe.

Removing the source of moisture will allow the wood to dry out so that action can be taken to bring the problem under control.

Affected timbers should be removed and replaced with pre-treated timbers. Any 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 severely damage a structure and, if left unaddressed, is likely to be invasive and expensive to rectify.

If you have any concerns about the potential for dry rot within your property, contact your local independent Chartered Surveyor or a dry-rot specialist  who can offer an expert opinion.