Dry & Wet Rot

Wet Rots and Dry Rot can be easily misidentified by the layman.  However, it is always sensible to get any fungal growth checked by an expert.  People assume that Wet Rot affects wet timber and Dry Rot affects dry timber but, in fact Dry Rot requires a high moisture content within the timber.

It often affects timbers located next to damp walls and likes humid, unventilated spaces in buildings.  Once established it is very persistent and, will travel long distances, often behind wall plaster to find further damp wood to devour.

Affected timber shows signs of cuboidal cracking and when severely affected, crumbles readily into fine powder.  Fungal mycelium develops on the surface of the timber, sometimes this mycelium looks like a white, cotton wool cushion, which spreads across timbers and brickwork.  Strands radiate from the initial outbreak and can extend for several feet across inert materials such as bricks and steel joists etc.

The fruiting body resembles a flat plate or bracket.  They are initially pale grey but as spores develop on the spore-bearing surface, it becomes rusty red in colour.  Millions of spores are produced and this gives rise to the characteristic red dust which can cover a floor.

Treatment must be a comprehensive sterilisation to one metre beyond the last visible sign of growth and it is essential to determine the full extent of the outbreak and ensure that no infected timber is overlooked.  All fungus growth will need to be traced to its origin and all hidden timbers uncovered.  It is also essential to locate and rectify the source of moisture ingress giving rise to the fungal decay.

This type of Rot can cause extensive damage to a property and it is always advisable that a survey is carried out as quickly as possible once an outbreak is suspected.

There are a wide variety of fungal species which cause Wet Rot Decay, some of which may cause a darkening of the timber (Brown Rot) or a bleaching effect (White Rot).  Unlike Dry Rot, Wet Rot does not have the ability to spread, it does not produce well developed strands and does not penetrate brick walls in the same way.

Coniophora Puteana (Cellar Fungus) This type of Wet Rot is the commonest cause of decay in woodwork which has become soaked by water leakage. The wood darkens with cracks along and across grain and often in conditions of high humidity, mycelium growth is present.

Fibroporia Vaillantii (Mine Fungus) This type of Wet Rot often occurs on timber in humid conditions and produces a white fern like mycelium growth. It often resembles Dry Rot where the wood breaks up into cuboidal pieces but decayed wood is lighter in colour and cracks are not as deep as those caused by Serpula Lacrymans.

Donkioporia Expanse This is a White Rot and is most common in hardwoods, particularly oak, although may spread to adjacent softwoods.  The wood often becomes bleached and when decayed is easily crushed. A distinctive fruiting body can sometimes be present, brown in colour with several pore layers.

Asterostroma spp A Wet Rot which usually affects softwoods and mainly found on joinery timbers, such as skirting boards.  The wood becomes bleached and has a fibrous appearance. There is no cuboidal cracking and damage is often limited in its extent.

Peziza spp (Elf cap) This is a non-wood rotting fungi and is often found on damp brickwork or plaster. It feeds on surface detritus or organic materials included in walls such as hair contained in old plasters or bituminised felt damp proof courses.