Woodworm: Active vs Historic Infestation

"Woodworm" is a catch-all term for the wood-boring larvae of several beetle species, with the Common Furniture Beetle (Anobium punctatum) being the most common. Discovering boring holes in floorboards or loft timbers can cause panic, but is the infestation still active, or did it end decades ago?

Spotting and Checking Woodworm Holes

When adult beetles emerge from timber, they leave tiny round "flight holes" about 1.5mm to 2mm in diameter. However, these exit holes can remain unchanged for hundreds of years. To determine if an infestation is active, look closely for frass—a light-colored, powdery wood dust beneath the holes. Active beetle emerging typically occurs from May to September. Fresh frass has a warm, cream color and the texture of fine grit.

Timber Moisture Influences Beetles

Wood-boring beetles struggle to survive in dry timbers. If a home has a healthy relative humidity, wood moisture content generally drops below 12%, making it too dry for beetle larvae to feed. If timber moisture climbs above 16% due to poor ventilation, leaks, or condensation, the larvae thrive and eat faster, weakening structural floor joists and rafters.

Insect Treatment Guidelines

Historic woodworm requires no chemical treatments; simply monitor the timber. Active infestations require targeted remedial action, starting with sealing moisture leaks to dry the timber. Timber surfaces should then be treated with a child-safe, odorless water-soluble boron wash, which eliminates wood-boring insects permanently.