For practical purposes, decay in house woodwork can be classed as cither wet rot or dry rot.

Wet rot is caused by fungi that can only spread as far as the moisture has pene¬trated and their strands (root-like growths) cannot penetrate brickwork. There are a number of fungi that can cause this type of rot. In floors the most common one is the cellar fungus, Conio-phora puteana (formerly C. cerebelld). This makes affected wood darken and leads to cracks forming which mainly run along the grain of the wood. The fungus often forms narrow, dark brown strands on the surface of the wood.

Dry rot is a much more serious type of decay which, in the UK, is caused by the dry rot fungus Serpula (formerly known as Merulius) lacrymans. Like all other fungi, it needs damp conditions  to become established, but once it gets a hold it forms root-like strands, some¬times as thick as a pencil, which enable it to spread into surrounding less damp timber and to penetrate through walls and masonry. The infection can spread from one room to another and the strands can be found in walls between the plaster and the brickwork. They can also travel through mortar joints seeking out any pieces of timber in the walls.

Wood attacked by dry rot tends to break up into dry brick-shaped pieces and usually has grey, fell-like growths of fungus on its surface. However, if the air around the fungus is very moist, it can form white, fluffy cotton wool-like growths which often have tinges of lilac or yellow on them. When the fungus has been growing for a year or two, it pro¬duces fruiting bodies on the surface of the wood or on adjacent brickwork. These are pancake-shaped with a wrin¬kled surface that soon becomes a bright, rusty red colour as the spores (seeds) develop. These spores are minute, oval cells about 0.01mm long. They are pro¬duced in such abundance that the sur¬rounding surfaces soon become covered with what looks like a fine, rust-coloured dust. When this dust is found on the surface of a floor, it is a sure indication that the dry rot fungus is present some¬where nearby. Sometimes the appear¬ance of the fruiting body is the first indication that dry rot has attacked your timber.

Mould is the least worrying fungal growth that is likely to attack your house. Heavy growths of mildew and dark-coloured moulds may develop as a result of condensation on cold walls. This indicates that there is lack of venti¬lation and insufficient heating and


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