How To Identify Dry Rot Fungus

Dry rot fungus is a serious problem. Left untreated it can eat its way through all the wooden structures in your home seriously weakening flooring, roof beams, stairs and any other wood in your property leaving it dangerous and inhabitable.

Luckily it can be treated and if caught early you can escape serious damage. It is, therefore, important to educate yourself about what is dry rot, the causes and early signs of dry rot, and its progressive stages. This guide will help you to do that as well as go through some of the wood rot treatments that are available.

What is Dry Rot?

Dry rot is a type of fungus called Serpula lacrymans that thrives in damp wood. It can spread throughout your home easily because it can travel through masonry as well as wood.

Despite the name dry rot, wood needs quite a high water content for this type of fungus to take hold. The name stems from it being found in ‘dry’ or seasoned wood, in other words, timber that is ready for use in building, furniture or other industries.

Dry Rot vs Wet Rot

Dry rot and wet rot are two different types of fungus. Dry rot is Serpula Lacrymans and wet rot is Coniophora Puteana.
Of the two, dry rot spreads more easily and therefore is more of a threat to your property. Wet rot though still damaging usually remains more localised.
Both of these fungi thrive in wet conditions with dry rot taking hold in wood with a water content of 20-30% but wet rot, true to its name, requires a higher water content of around 50%.

What Causes Dry Rot?

A mix of airborne spores of the dry rot fungus and water causes dry rot. Therefore leaking pipes, leaking appliances, faulty guttering, condensation, penetrating damp, and broken roof tiles among other things can be the start of dry rot problems.

Stages/Signs of Dry Rot

Damp Smell

A damp musty, mouldy smell can be an early indicator of dry rot.

Spore Dust

The spore dust of Serpula Lacrymans is typically orange, rust-coloured or brown. If these spores come into contact with wood with a suitable water content dry rot will develop.


Once the spores have found the right conditions, i.e. damp wood, they grow into grey hair-like strands called hyphae. These penetrate and grow through the wood.


Similar in appearance to cotton wool mycelium grows from the hyphae. It is the mycelium that spreads looking for more wood to devour and can even travel across masonry (though it does no damage).

Timber decay

Wood that is dry, crumbling and/or cracks in square or rectangular patterns is likely to have a dry rot problem. It is better to get the dry rot problem treated well before it gets to this late stage when timbers in your home may need intensive work or replacement.


The mushroom or fruiting body of the dry rot fungus is round and flat, like a thick plate and is an orange and/or rusty red colour. They can appear in many different sizes, in extreme cases, they have been seen at over 2m in diameter.

Treatment for Dry Rot

If you suspect that you may have a dry rot problem in your home the first thing to do is get a survey to confirm that is the issue. Once the presence of dry rot has been confirmed then dry rot treatment can commence.
The first step is the find the source of the damp and get that issue resolved. Otherwise, the dry rot will recur. Once your home is adequately damp-proofed then all the affected wood will need to be removed.
All the existing wood in the property will then need to be treated with a fungicide.

What to do if you Suspect You Have Dry Rot in Your Home

If you live in London or Surrey and suspect you have dry rot then get in touch with us at RBS DampProofing. Our specialist team will conduct a survey, damp proof your home and treat your dry rot with minimum fuss and at affordable prices.

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