Most people find woodworm the same way: lifting a carpet, clearing a roof space, or pulling up a floorboard, and spotting a scatter of small round holes in the timber. The immediate question is not what is this — most people know woodworm when they see it. It is whether it is still happening.
That matters commercially, because dormant woodworm from forty years ago needs nothing done to it, and an active infestation needs treating before it costs you structural timber.
What woodworm actually is
"Woodworm" is not one insect. It covers several wood boring beetles whose larvae feed on the cellulose in timber. The damage you see is not caused by the beetle you might find — it is caused by the larvae tunnelling through the wood, sometimes for three or four years, before maturing.
The holes are exit holes. An adult beetle bored out through the surface to fly off and lay eggs elsewhere. That is why holes alone tell you an infestation happened; they do not tell you it is ongoing.
Four signs it is active
1. The holes look fresh
Active exit holes are clean, sharp-edged and light in colour inside — the shade of freshly cut timber. Old holes darken, fill with dust and grime, and often get painted or varnished over. If you can see holes with pale, crisp edges, something has emerged recently.
2. There is frass, and it is loose
Frass is the powdery bore dust larvae push out. It looks like fine sawdust or gritty talc, usually cream or light brown, and it collects directly beneath the holes.
The key is whether it is loose and clean. Fresh frass is powdery and moves if you brush it. Old frass compacts, greys, and gathers cobwebs and general dust. Sweep an area clean, come back in a fortnight, and if there is fresh powder again you have a live infestation.
3. You are finding beetles
Adult beetles emerge in spring and summer, typically May to August, and head for light. Live or dead beetles on windowsills near affected timber during those months is a strong indicator.
4. The timber is weak
Press a screwdriver into the wood at the edge of the holes. Sound timber resists. If it crumbles or the blade sinks in, the tunnelling network has already taken the strength out of that section — and that is a structural question, not just a beetle question.
Why this is genuinely hard to judge
Two things make honest self-diagnosis difficult.
First, dormant does not mean gone. Timber that has been treated, or where the beetles have moved on, can look identical to active infestation for years. The difference is often just whether the frass is fresh — and if the timber has been disturbed recently, that signal is unreliable.
Second, and more importantly: woodworm is usually a symptom. Wood boring beetles need timber above a certain moisture content. Timber that is dry does not sustain most infestations. So if you have active woodworm, something is keeping that timber damp — a leak, poor ventilation, a failed damp proof course, condensation in an unvented roof space.
Treating the beetles without finding the moisture is treating half the problem. This is the single most common reason woodworm comes back.
What to do about it
If the signs above suggest activity, or you genuinely cannot tell, get it surveyed. The point of a survey is not to sell you treatment — it is to establish whether the infestation is live, what species it is, how far it has gone, and what is keeping the wood damp enough to support it.
Our surveyors will lift floorboards or get into roof voids to see the affected timbers properly, because you cannot assess this from a doorway. You then get a written report with the cause, the recommended work and the cost, before you commit to anything.
If treatment is needed, our woodworm treatment uses a low-odour, water-based microemulsion insecticide. It kills the larvae active in the wood and penetrates the surface to protect it against reinfestation. Properties we treated three decades ago have been inspected since with no sign of the woodworm returning.
If the timber is soft rather than holed
If your main symptom is timber that feels soft, spongy or crumbling rather than peppered with holes, you are probably not looking at woodworm at all — that is more likely wet or dry rot, which is a fungal problem and needs a completely different approach.
And if there is damp involved but you are not sure what kind, our guide on rising damp versus condensation covers how to tell those apart before anyone quotes you.
Getting it looked at
We have been treating woodworm across Northern Ireland since 1967, in everything from Belfast terraces to listed buildings and churches. If you would like a surveyor to take a look, get in touch or ring 028 9061 8343. We cover the whole province — see areas we cover.