How to Identify Dry Rot

Without industry training and experience, it can be difficult to differentiate between dry rot and wet rot due to the fact that both types of rot share a number of tell-tale signs.

Both these forms of rot cause timber to crack, leave affected areas soft and spongy and can lead to fungus-like growth on timber.

One of the main differences between dry rot and wet rot is that wet rot requires a higher moisture content of around 50% whilst dry rot will grow with a moisture content of around 20-30%. Because of this, wet rot will only be present near a prevalent moisture source and as such is often found in the vicinity leaking appliances, burst pipes or window sills. In contrast, dry rot can spread over relatively dry timber if the humidity is right.

Due to the difficulties in identifying the type of rot, we would recommend contacting a rot specialist who can examine any affected timber and establish if there is a rot outbreak

Damp Smell - The Dry rot smell is a distinct musty mushroom smell.

Spore Dust - Large concentrations of fine brown dust can indicate an outbreak of dry rot is present.

Hyphae - Fine strands of fungal growth dry rot spores produce when they come into contact with timber in damp and humid conditions. They grow by extracting the moisture from timber.

Mycelium - As the hyphae grow, the strands combine to form a white cotton wool-like fungus called Mycelium to spread to new timber surfaces.

Timber Decay  - As it develops, timber affected by the fungus will begin to discolour, darken and become brittle with cuboidal cracking.

Dry Rot Fungus - A mushroom-like orange fungus, the fruiting body of dry rot can be found in warm, damp, dark ventilated places to grow such as under floorboards, cavity walls or in the attic.

You may wish to take a look to see how these rot symptoms differ from other signs of damp on walls.

Dry rot spores are always present in the atmosphere, however, they are harmless unless the right conditions are present. To develop into an infestation, a damp problem and a lack of ventilation are required in the property

Dry rot starts when these spores land on timber with moisture content over 20% they will then begin to germinate and produce hyphae (fine strands of fungal growth) that are greyish in colour. This will develop into mycelial growth which varies from grey to pure white in wet conditions. It is at this stage in the dry rot life cycle that Sporophores or fruiting bodies will begin shedding millions of spores in the form of red dust, so the process repeats itself and the infestation becomes more entrenched in the home.

Although individually these spores are almost invisible to the naked eye, In houses with dry rot problems you will often find that when they group together they appear as a tell-tale fine orange or brown dust.

Once the hyphae strands are formed, they join together to create a mass called Mycelium which can vary in colour from grey to pure white, and these strands grow into and across damp wood and masonry. It can also grow over materials such as plaster, mortars, bricks etc as it searches for more cellulose-containing timber to feed on.

When the growth is advanced a fruiting body (Sporophore) may develop. This fruiting body takes the form of a “fleshy pancake”, the surface of which is orange/ochre-coloured.

For more help and advice to identify and treat wood rot take a look at the links below.