Timber decay occurs when the timber has a moisture content of 18% or above, the most common problem being wet rot which is caused by timber being in contact with damp walls or poorly ventilated sub-floors that allow excessive condensation to occur and causes the onset of rot and or woodworm infestation to the timbers. It is important to diagnose the problem correctly as some surveyors commonly confuse wet rot with dry rot and the common furniture beetle widely referred to as woodworm with the wood boring weevil which do not require any chemical treatment.
The most common wood rotting fungi is known as Coniophora Puteana or cellar fungus which is normally present in timber in contact with damp walls or when timber has become soaked by water leakage. The wood darkens and cracks both along and across the grain but usually less deeply than with dry rot. As with all types of rot the source of moisture must be eliminated and sub-floor ventilation upgraded where necessary, the affected timbers are then removed and replaced with new preservative treated timbers.
The true dry rot fungus Serpula Lacrymans is known as the cancer of the building trade. Unlike wet rot, for which relatively simple procedures are adequate for control, the successful treatment for dry rot may require elaborate and sometimes expensive control measures. It is important therefore, in the first instance that an outbreak is identified correctly. Dry rot most typically occurs in locations where timber is in contact with damp brickwork and where ventilation and heating are inadequate, for example in poorly ventilated sub-floors and behind panelling. The fungus requires cellulosic materials as a food source and grows most rapidly on wood that has a moisture content of above 30%.