Dry Rot and Wet Rot

Most dwellings in the UK contain timber in some form or another.  It could be to create timber floors, timber roof trusses, doorframes, fence posts sheds, or furniture.

Whether the timber is a hardwood (Angiosperm), or softwood (Gymnosperm), all timber is part of the carbon cycle and the development and degradation of timber is part of this.

All timber relies on water for growth and in its natural environment, the fungus that causes decay relies on this as well.

When we utilise timber in construction, the timber is artificially dried.  This changes the materials properties and makes it suitable for use. However, if the material is not placed properly or protected adequately from sources of moisture, then the timber may be susceptible to fungal decay.

Sources of unwanted moisture can be from timber in contact with damp ground, timber embedded into a damp wall, excessive moisture building up in an unventilated cavity, and sources of penetrating damp saturating structural elements.

Generally, it is quite hard to identify what type of fungus has infected the timber. However, the main factor to identify is whether the infection it is a form of dry rot, or wet rot, as the remedial measures for dry rot are much more extensive.

Note: the term dry rot is a misnomer. The fungus associated with this is called Serpula Lacrymans and was initially named so as the fungus was thought to originate from fermentations within the timber. Later studies of the fungus found that although the fungus can develop at lower moisture levels, the fungus does require moisture to develop and propagate and the absence of moisture would kill the fungus.

Today types of fungus are defined into the category of either brown rot or white rot, some examples of these are:

Brown Rots

• Dry rot – Serpula lacrymans
• Cellar Fungus – Coniophora puteana
• Mine Fungus – Fibroporia vaillantii

White Rots

• Donkioporia expansa
• Phellinus contiguus
• Asterostroma spp

Dry rot treatment is generally more extensive due to the fungus’s unique ability to grow through organic material, to find sources of moisture, therefore the material can be quite pervasive in spreading throughout the dwelling, whereas other types of fungus are generally localised to the source of moisture.