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Dry rot/wet rot

- the problems associated with the decay of timber in buildings have spawned a huge and often damaging industry, which has been able to feed on the ignorance, fear and panic which surrounds the subject. Much historic fabric has been needlessly removed, and toxic chemicals introduced into buildings simply because a naturally occuring process is so frequently misunderstood.

If timber components are kept dry ie there is no abnormal ingress of water into the building either in the form of rainwater or excess humidity, then they will be stable for long periods of time. However, excess moisture can allow the colonisation of timber by wood decay fungi, notably by organisms causing wet and dry rot. Wet rot is a generic term which covers decay ocurring in very damp conditions, eg by rot caused by the organism Coniophora puteana (often referred to as cellar fungus) identified by dark brown threads spreading over the surface of the timber. Dry rot is caused by Serpula lacrymans which is generally considered to be more dangerous than wet rot fungi, since it is less easily controlled by drying regimes. However, as for all wood decay fungi, it cannot operate in dry wood and removal of excess moisture from timber is the only long term method of control. Both wet and dry rot are types of "brown" rot, so called because ultimately the timber becomes a brown and dry dust.

Glossary
Dote - the name given to timber surfaces which have just started to break down due to fungal decay but which are still structurally sound. Also known as incipient decay. Timbers so affected are sometimes referred to as "dosy"
Fruiting body - see sporophore.
Hyphenium - the spore bearing surface of a fruiting body.
Hyphae - thin tubes or threads, which spread out from the seeds, across the surface of timber, feeding on the starch, sugar and moisture it contains.
Mycelium - a mass of hyphae.
Rhyzomorphs - thick strands produced by fungi eg Serpula lacrymans, which can conduct nutrients and moisture between areas of the organism. It is these strands, which, on the case of S. lacrymans can be up to 6mm thick, and can be found travelling across and through a variety of non woody materials, which makes dry rot particularly dangerous to buildings.
Sporophore - fruiting body of a fungus. Rarely seen for Coniophora puteana but quite commonly with other wet rotting organisms, often evident in dry rot where it can be a meter in diameter.