Woodworm in buildings

Woodworm infestation of untreated timber is a relatively common problem. The House Longhorn beetle was a particular problem in the UK prior to the introduction of pretreated timber in the 1960s.

The House Longhorn beetle measures up to 25 mm long when mature, and can lay up to 200 eggs on the rough surface of untreated timber. After 2-3 weeks, the larvae emerge and bore into the timber. They can be detected by the powdery deposits known as ‘frass’ left on the surface and the bore holes of around 3 mm diameter. They are attreacted to damp areas and timber with a high moisture content.

Other woodborer insects include:

• Furniture beetle: These are 6-8 mm long and lay 20-50 eggs on soft or hardwoods.
• Lyctus powder post beetle: These are 10-15 mm long and lap 70-200 eggs on the sapwood of new hardwood.
• Death Watch beetle: Around 7 mm long and lay 40-80 eggs on hardwood. Are a particular problem on oak timbers found in old churches and similar buildings.

Timber can be treated:by:

• A water-based boron treatment which can be sprayed or brushed on, or injected as a gel or paste.
• Ultraviolet insect killers.
• Fumigation or fogging.
• Replacing affected wood.
• Monitoring and improving conditions to prevent re-infestation.

A specialist survey may be necessary to determine the most appropriate form of treatment.

For more information, see also: Timber preservation and Woodworm and spiders.

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