Determining whether or not an outbreak of dry rot is alive can be diff~cult. Salient observations are shown in Table 3.
water in wood is intimately associated with wood fibres. As moisture levels increase above 20% enough water is available in the woody cell wall to allow degradative enzymes to operate and above around 25% moisture levels 'free' water is present. The point at which free water becomes available is termed the 'fibre saturation point' and it varies slightly from timber to timber. It is as well to be aware that, for the purposes of evaluation of risk of timber decay in buildings, precise moisture measurements in wood are of less importance than changes and trends within buildings. However any wood which contains moisture levels above the fibre saturation point is definitely at-risk
Despite these indications determining if dry rot is dead or alive is an imprecise business though diagnostic tests may become available in the next few years based on ATP or ergosterol measurements (both of these substances are transiently produced by live fungi), dye discolouration tests or electronic noses which can detect specific fungal volatiles. Trained dogs (as used by Hutton and Rostron Environmental Investigations Ltd and in Denmark) can give guidance, also by detecting fungal volatiles, but their reactions need to be evaluated by trained handlers. Of course, whether or not an outbreak is still alive is irrelevant if the 2-3-4 The environment S-lac~mans which supPO* growth remain. In such Dry rot caused by S.lacrymans is found throughout the conditions it will just be a question of time before an UK, in most of Northern and Central Europe and in active growh of the rot fungus is initiated either temperate sites in southern Europe, in parts of Asia and from extant live material or from a new source. Australasia but rarely in the Americas. However Of course development of the fungus will not happen S.lac~mans,is found only within buildings in almost in timber of low moisture content unless moisture can all of these regions and substantiated reports of its be transported to it. It is generally considered - though growth in the 'wild' (i.e. the extelllal el.lvir0nmeIlt) are difficult to measure precisely - that moisture levels in rare. SWgely perhaps, given its rampant nature in wood need to be o v a 20% (weight for weight) before buildings, the organism seems rather innocuous in its dry rot can develop from mycelial inocula and 30% natural environment suggesting there may be from spore inocula. This is not much higher than the unidentified factors limiting its growth h nature. One moisture level found in seasoned wood (around 12- such factor could be the Presence of competing 16%) but nevertheless it is a level that should not occur microorganisms, another could be the relative in a well maintained building. At low moisture levels, environmental sensitivity of S.lacr~mans.
Illustration 3. The Himulayan environment The natural habitat of the dry rot fungus appears to be the foothills of the Himalayas. Finds have been made by the group at the University of Abertay Dundee in conjunction with Dr Jagjit Singh, then of H&REI in the vicinity of Narkanda in Hirnachal Pradesh (India). Understanding the natural environment of the organism, and why this is so restricted, will assist in the development of new environmentalprotocols for controlling, and preventing, the growth of S.lacrymans in buildings.