What is dry rot?

Dry rot is an aggressive form of fungal growth also known as Serpula Lacrymans. It is a wood destroying fungi that feeds off the cellulose in timber in order to grow and spread. This process leaves timber in a dry and brittle state and can weaken structural timber in buildings as a result.

Keep reading this guide for expert help identifying the early signs of dry rot, understanding what causes it, and how to act quickly to repair any damage. The earlier you can identify dry rot the simpler and more cost-effective solving it becomes.
 
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Dry rot is caused when a source of moisture and a lack of ventilation combine creating the perfect conditions for an infestation to start. There needs to be a source of food for the fungal spore - typically susceptible wood - and when the spore lands on the timber with moisture content over 20%, the germination process can begin before producing hyphae.

The spores themselves are very small, about 0.01mm, and almost invisible to the naked eye.

However large numbers of these spores will frequently collect around a fruiting body and form a reddish ‘dust’, which is a key sign to identify a significant attack of dry rot is present.

Dry rot has a few ways to spread throughout its fungal life cycle. For example, during its mycelium stage, dry rot can grow over and through various materials, including brickwork and masonry, in its search for more timber to consume.

If light activates the mycelium,a mushroom-style fruiting body called a sporophore develops. This releases spores that look like red dust. These spores drift on air currents and germinate on suitable surfaces. So the life cycle turns full circle.

All of this means dry rot can spread throughout a property fairly rapidly if the conditions are right.

You can find out more about the stages of dry rot below.

Dry rot fungus is often accompanied by a smell which is a damp musty odour reminiscent of mushrooms. Sometimes if the fungus has taken hold in a basement, under floorboards or behind a wall, then this pervading damp musty smell is the first sign that makes people aware that rot is present in their home.

Dry rot is a specific species of fungus (Serpula Lacrymans) whereas wet rot is a name given to a variety of fungi that requires timber with a far higher moisture content to grow (around 50%).

Wet rot usually affects timber at the source of the damp and will cease to grow when the source of moisture is taken away meaning it is often more localised.