Timber problems come in all shapes and sizes, from woodboring insects to types of rot and the solution very much depends on the correct diagnosis of the problem.
In terms of wood-rotting fungi, probably the first thing we consider is whether it is Wet Rot, or Dry Rot. If it is Dry Rot, we know that there is just one type and that is “Serpula Lacrymans”. If it is Wet Rot, there are numerous different types, including, the most commonly found, types, which are; “Coniophora Puteana”, “Fibroporia Vaillantii”, “Phellinus Contiguus” and “Asterostrama”. Another thing which complicates things a little further is categorizing the rots into either Brown Rots, or White Rots. This is not straightforward because although there is only one type of Dry Rot, it is actually categorized as a Brown Rot. Whereas the first two of the aforementioned wet rots are Brown Rots and the next two are White Rots.
Brown Rots tend to cause the wood to darken in colour and affected timber will generally crack across the grain – cuboidal cracking. Where timber subjected to fungal attack has dried, very decayed wood will crumble to dust.
White Rots cause the wood to lighten in colour and take on a bleached look. Decayed wood will become almost fibrous in texture and without cracking across the grain. This type of rot can often be found to be affecting external surfaces of window frames and surrounds.
What is Wet Rot?
The most commonly found type of wet rot – especially in floor timbers such as joist ends, timber wall-plates etc. is ‘Coniophora Putana’ or ‘Cellar Fungus’. As the name implies, wet rot grows on wood where the moisture content of the timber is generally 25-28% or above where the moisture and humidity will help the spores to germinate. It can be found in damp basements, under floors and in skirting boards and prefers areas with insufficient ventilation. Keys to identification of this – and other types of wood-rotting fungi – are the type and colour of the sporophores (or fruiting bodies) the type and colour of the hyphae strands and the type and colour of the mycelium. It is really important to identify these things correctly so that the correct specification for eradication is proposed.
How does it cause damage?
It can be very destructive, as the fungi steals nutrients from the wood where it grows, thus weakening wood and in some instances, causing structural instability.
How can I prevent it?
Timber in buildings provides an ideal food source for fungal growth but only if the conditions are right for such growth. Where moisture levels / moisture contents in timber are less than 20%, fungal decay will not start to grow. The excess moisture levels noted earlier (25-28%) are necessary to support spore germination and allow fungal growth to begin. Therefore, it is really important to rectify any plumbing leaks, rising damp, condensation, leaking roof coverings, defective rainwater goods and any other causes of rainwater penetration to help prevent an outbreak of fungal decay.
What is Dry Rot?
Dry rot is caused by a wood destroying fungus know as ‘Serpula Lacrymans’ and contrary to its name, it still relies on timber having a moisture content of around 25-28% to grow. Infections of Dry Rot in a building can be extremely serious as it is hard to eradicate and may require drastic remedies.
How does it cause damage?
Serpula Lacrymans causes decay by removing cellulose and hemicellulose from the timber, leaving a brittle matrix of modified lignin.
How can I prevent it?
As with wet rot, it is important to rectify, plumbing leaks, rising damp, causes of rainwater penetration, condensation and leaking roof coverings to prevent an outbreak. Once you have rectified any issues it is important to look for any signs of dry rot as it may still be active within the timber. Dry Rot has the ability to grow behind and within non-organic materials such as plaster, mortar joints, hardcore under solid floors etc to find new sources of food. It is important to have any area inspected by a qualified CSRT surveyor, who can provide a full report and specification for necessary remedial action.
How can I tell if I have Dry Rot?
Decayed wood takes on a dark, crumbly appearance with very distinct cuboidal cracking. The wood becomes brittle and eventually the wood can be crushed into powder. You may notice white, fluffy mycelium which look a little like cotton wool if the conditions are humid whereas you may notice a mushroomed coloured skin with patches of yellow and lilac if it is less humid; this skin can be peeled off. Fruiting bodies may also be visible; these are orange in colour and their surface has wide pores; One real tell-tale sign, is the appearance of a dark reddish-brown coloured dusting over surfaces. This is the result of millions and millions of tiny spores being released from the sporophore (fruiting body). There may also be a sweet, mushroom type of smell.
What should I do if I have Wet or Dry Rot?
If you suspect that you have any form of wet or dry rot, the best course of action is to contact a Company affiliated to the PCA and arrange for an inspection by a specialist, qualified, CSRT Surveyor who can diagnose the extent of the problem and the offer the best solution.