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
Whether by flooding, burst pipes or damping down after a fire, introducing a large volume of water into a building has an impact on the structure long after the cause has gone. For a situation that occurs routinely there is a surprising amount of variation in the way that buildings are dried. The methods employed to dry a building and the manner in which they are implemented can have a significant influence on the susceptibility of its structural timbers and their susceptibility to fungal decay. By developing an understanding of the building’s construction and the ecology of the fungi most likely to colonise it, damage can be minimised.
Through specialist surveying and monitoring of water-damaged buildings it is possible to anticipate the problems they may encounter through the drying process and formulate bespoke recommendations for the building. A building saturated by large amounts of fresh water represents a different environment to structures that have been made comparably wet through different circumstances. Damp cellars, earth retaining walls and leaking roofs may have timbers containing comparable amounts of water but the decay fungi found are quite different. Equally, the species of timber used in the construction and its quality can provide a great deal of information as to how the building will dry and from which decay organisms the building fabric is at most risk. Modern building timbers are less durable than those used a hundred years ago, particularly if they have not been preservative treated. They present a greater risk of decay.
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Examples of Pyronema sp. (Click on the above images for larger versions)
In the first stage of drying, where water evaporates unhindered from surfaces and large diameter pores of the masonry and brickwork, mould growth can be expected within a matter of days. Whilst there are a wide variety of moulds that can be found following fires and floods, it is worth mentioning Pyronema domesticum which is common following fires. This can produce a large amount of white fluffy surface growth (mycelium) and can be confused with the more serious fungus: Serpula lacrymans (dry rot). Whilst it can grow across plaster and on timbers and be unsightly, it does not cause decay.
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Examples of Serpula lacrymans (dry rot) (Click on the above images for larger versions)