Woodworm treatment
Identifying woodworm
Woodworm holes of 1 to 2 mm point to the common furniture beetle. Fresh, sharp-edged holes with pale dust below are active; dark, weathered holes with no dust are usually old.
- Hole size shows the beetle
- Active or old?
- The dust test and the season
- Where woodworm turns up
- What can look like woodworm
- Why the answer matters when selling
- What to do next
Hole size shows the beetle
"Woodworm" is the grub stage of wood-boring beetles. The adult leaves a round exit hole as it escapes, and the size points to the species.
- Furniture beetle: 1 to 2 mm. This is the usual UK culprit.
- Deathwatch beetle: 3 to 4 mm.
- House longhorn beetle: 6 to 10 mm.
Large holes need a specialist's eye: deathwatch and longhorn beetles can affect structural timber.
Active or old?
Active signs: fresh holes with sharp, clean edges; fine pale dust, called frass, below the holes; dust trails on vertical surfaces; dead beetles on windowsills.
Old signs: dark, weathered edges around the hole, no dust, and solid wood when you probe it with a screwdriver.
Many woodworm holes are old. The Property Care Association says an infestation may have died out because the timber dried or was treated before, so holes alone are not a reason to treat.
The dust test and the season
Beetles emerge from May to September, peaking in June and July. That is when fresh dust appears. To test, clear all the dust in autumn, then check again between June and August. New dust means the beetles are still active.
Surveys can be done all year, but this test works best in summer.
Where woodworm turns up
Look at floorboards and the joists below, stair parts, skirting boards, window frames, loft and roof timbers, and old furniture. Damp or poorly ventilated areas are the most likely, such as under-floor voids and roofs with leaks.
Probe suspect wood gently with a screwdriver. Solid timber suggests an old problem. Soft or crumbling wood suggests rot or serious damage, and a specialist should look at it.
What can look like woodworm
Filled nail holes, mortar bees and wet or dry rot can all be mistaken for woodworm. Rot softens and cracks the timber rather than leaving neat round holes, and it points to a damp problem that needs a different fix. A PCA-qualified surveyor can tell them apart. See damp proofing if you suspect moisture is the real cause.
Damp timber is what drives woodworm. Low moisture content makes infestation unlikely.
Why the answer matters when selling
A buyer's survey may flag woodworm from holes alone. A report showing the holes are old, or a guarantee from earlier treatment, can settle the point. Sellers should also disclose known treatment on the TA6 form. Lenders may impose a retention if the evidence is unclear.
What to do next
If the holes look old, you may only need to monitor them. If you find fresh dust, book an independent survey with a woodworm specialist. A surveyor confirms activity, the species and the moisture level before recommending treatment. For a small piece of furniture, the DIY guide covers what you can do yourself.
Will the council do it?
Councils rarely treat woodworm. Use a private firm, and ask the questions below before you book. See what your council treats
Questions people ask
How big are woodworm holes?
About 1 to 2 mm for the common furniture beetle. Deathwatch beetle holes are 3 to 4 mm and house longhorn holes 6 to 10 mm.
How do I know if woodworm is active?
Look for fresh holes with sharp, clean edges and fine pale dust beneath. Old holes have dark, weathered edges and no dust.
When do woodworm beetles emerge?
From May to September, peaking in June and July. Clear the dust in autumn and check again in summer.
Can woodworm holes be old?
Yes, very often. The infestation may have died out because the timber dried, or because it was treated in the past.
Is woodworm the same as dry rot?
No. Woodworm is a beetle grub. Dry rot is a fungus that decays timber. They need different treatment, so ask a surveyor to tell them apart.