How to deal with woodworm

A peppering of tiny woodworm holes adds rather a distinguished note of character to old timbers, but doesn’t necessarily mean you have uninvited guests because the infestation could be long since dormant. In this article we look at what the term ‘woodworm’ encompasses, how to go about identifying the species, the damage woodworm can cause and the various treatments available.

Woodworm can be found in any part of your home where there is timber, if the right conditions exist for the infestation. Different species of woodworm have preferences for varying types of timber and situations, for instance: roof joists, skirting boards, floorboards or joists and furniture. Typically, though not exclusively, the woodworm also prefers damp conditions.

• Not all woodworm needs specialist treatment so seek advice from more than one source
• Always seek a guarantee for any work carried out
• Woodworm holes can be filled with beeswax and turpentine (or left to add character!)

Scroll down to the following sections for advise:

• What is woodworm?
• What are the symptoms?
• How do I identify species?
• How is woodworm treated?
• How much does it cost to treat?
• How do I prevent woodworm returning?

What is woodworm?

Woodworm isn’t confined to one particular species; it actually refers to the larvae of any wood-boring beetle. The most common form is the Common Furniture Beetle (Anobium punctatum) but Deathwatch Beetle (Xestobium rufuvillosum) and House Longhorn Beetle (Hylotrupes bajulus) may also be present.

Typically beetles prefer damp conditions, specifically timber with a moisture content of 18% or more. Having found a nice damp spot, beetles lay their eggs and it’s their larvae that do the damage, burrowing beneath the surface of the wood eating their way up and down the timbers until pupating and hatching out, boring their way into the open air through “flight holes”. So the presence of holes actually indicates that there has been an infestation, not that there is still an infestation.

What are the symptoms of woodworm?

To determine whether your woodworm are still active look out for the following activity around the holes in your woodwork:

fine powdery bore dust coming out of holes

adult beetles emerging from the holes (particularly during the April-September

period when they emerge from the wood to breed) or present in your house

presence of larvae when the surface of the wood is scratched away.

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How do I identify my species of woodworm?

Not all woodworm are harmful so the first step is identifying your species before deciding on treatment. 

• The Common Furniture Beetle typically attacks softwood species leaving tiny holes measuring 1-2mm. Damp floorboards, loft timbers and old furniture are favourite destinations, particularly where the finish or polish has worn off.
• The House Longhorn Beetle is rare. The beetle favours roof timbers where it attacks the sapwood of exclusively softwood species, leaving holes that are significantly larger than the Common Furniture Beetle and causing severe structural weakness.
• The Deathwatch Beetle loves wet, decaying hardwoods like oak, ash and chestnut. The damage this beetle causes can be more extensive than first thought because the larvae tunnel towards the centre of the timber; also because it has a 10 year lifecycle.

How is woodworm treated?

• The Common Furniture Beetle rarely causes structural weakening so DIY treatment is recommended. Two coats of water-based, vapourless and odourless ‘boron’, either brushed or sprayed on, should do the trick.

How do I prevent woodworm returning?

• Keep humidity levels low and ensure good ventilation. 
• Remove and replace affected wood to avoid woodworm spreading.
• Install ultraviolet insect killers to kill emerging adult beetles between April-September.