Woodworm in buildings
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.
 Find out more
 Related articles on Designing Buildings Wiki
- Ancient Woodland.
- Building preservation archive.
- Confederation of Timber Industries.
- Cross-laminated timber.
- Defects in construction.
- Domestic roofs.
- Dry rot fungus.
- European Union Timber Regulation.
- Flat roof defects.
- Flooring defects.
- Laminated veneer lumber LVL.
- Recognising wood rot and insect damage in buildings.
- Roofing defects.
- Timber framed buildings and fire.
- Timber preservation.
- Woodworm and spiders.
‘Structures and structural failure’ at IHBC’s Nottingham School, with Ed Morton (ex Canterbury, York and Westminster to St Paul’s) and John Ruddy.
Ageing gracefully - restorations which retain historical decay.