"Woodworm" is the most common cause of insect attack of softwoods in buildings, and is often to be found in structural timbers, roofs, floors and joists. The female adult beetle lays her eggs onto the susceptible timbers, and they hatch into larva which in turn burrow into the timber, gradually weakening it. This process can take at least three years, with the larvae growing to a length of 2.5mm. After the pupal stage, the adult beetles emerge from the timber through a 2mm flight (exit) hole.

Deathwatch beetle
The deathwatch beetle causes deterioration in structural hardwoods such as oak, elm and chestnut, which have already been partly decayed by wet rot. This pest is more of a threat to large timbers in older buildings and occurs mainly in the Southern and Central areas of England and Wales. It has yet to be recorded in Scotland.

Wood-boring weevils
After the Furniture Beetle, wood-boring weevils are probably the most common timber pest. They are commonly found attacking partly decayed wood, with both adults larvae causing the wood to break down by burrowing, principally along the grain, and leaving thin paper walls of wood separating the borings. of more commonly found in flooring, plywood and furniture. Flight holes are ragged in outline and less than 2.5mm in diameter.

House longhorn beetle
This beetle a notifiable pest causes severe damage to the sapwood of softwood roofing timber in parts of Surrey, Hampshire and Berkshire. The larvae burrow into the timber and, when fully grown after anything from 3 to 11 years, can measure over 25mm in length. The adult emerges through a flight hole 6 - 8mm in diameter.

Dry rot
This fungus mostly causes decay in areas with restricted ventilation, high humidity and a moisture content of between 30-40%. However, dry rot can remain active in timber with as little as 20% moisture and can also attack dry timber. It can grow through the fabric of a building if conditions are suitable, by penetrating brickwork and masonry and behind plaster, decaying any timber in its path. Decaying timber develops "cuboidal" cracking and is usually overgrown by masses of grey-white mycelium. Plate-like fruiting bodies produce millions of rusty-red spores (seeds) as a reddish dust, and these spores spread the fungal infection to other areas.

Wet rot
Wet rot develops as a result of rain water penetration, such as in the opened mitres of door and window frames, where paint films have broken, where plumbing is faulty or a major leak is occurring. High moisture levels (of 40 - 50%) are necessary for wet rot to develop, and the wood characteristically splits along the grain where decay occurs. There is usually a small amount of surface mycelium, but fruit bodies are not common.