Water damage in buildings and the prospect of timber decay
Should timber decay be expected without question, and what can be done to minimise the risk?
by Dr Matthew Green
Whilst dry rot will not attack timber outside the zone of wetting, in a flood damaged building this may be a significant surface area, much of which may be hidden from view. The presence of the dry rot may only come to light once the building starts to dry as it will produce fruiting bodies, often on visible surfaces to allow spores to travel and the timber it has attacked distorts as it dries. Thus, what is frequently interpreted as a dry rot problem is actually the end of one. Also, during any exposure works, historic dry rot outbreaks that have grown and died out without being noticed may be revealed and mistaken for a recent issue. In most cases, by the time the fungus has been uncovered it is usually dying. Halting water ingress and drying the building will kill it. Dry rot is like any other fungus: it cannot live without water, but it may survive for long periods within damp building fabric.
A little knowledge regarding the ecology of building fungi can minimise the risk of attack. Removing wet debris and promoting ventilation under timber floors by removing perimeter floorboards speeds up the drying process and reduces the likelihood of fungal decay.
In summary, the key points to reduce the likelihood of a decay outbreak following flooding include:
• Rapid clearance of building debris particularly from areas on or around timber floors and joinery
• Focussing drying in areas where modern timbers with lower durability have become saturated
• Exposure and monitoring of areas known to have had problems with timber decay in the recent past (particularly in the case of dry rot)
• The promotion of increased ventilation and air-flow across
affected walls and beneath timber floors that have been cleared of debris
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