Inspired by a helpful UK timber treatment guide. This walk-through is based on the popular video "Treating Woodworm: A Complete Guide" by Permagard Products Ltd, a UK timber and damp treatment specialist. It covers identification and treatment clearly, and is particularly useful for understanding the difference between active and old inactive infestations — a distinction that matters a great deal before you reach for the chemicals.
1. Look for the signs of woodworm
Woodworm is the larva of the common furniture beetle (Anobium punctatum). The adults emerge in spring and early summer, leaving small round exit holes roughly 1–2mm across in the timber surface.
Alongside the holes, look for fine powdery dust called frass — it looks like very fine sawdust and falls out of the holes or settles below them. Fresh, pale-coloured frass is a sign the infestation is active. Old, darker frass or holes alone may mean the beetles have long since moved on.
2. Check whether the infestation is still active
This matters. Old woodworm holes with no fresh frass and no new holes appearing are almost certainly inactive. Treating dead infestations is unnecessary and a waste of money.
The beetles emerge between May and September. If you find fresh pale frass in this window, that is your confirmation the infestation is live. Outside that season, cover suspicious holes with masking tape and check back in spring. If holes appear in the tape, they are active.
3. Assess the structural damage
Run a penknife or pointed tool across the timber surface in the affected area. If the wood crumbles or feels very soft, the larvae have caused significant damage. Probe any joints, the underside of floorboards, and any structural beams.
Surface holes with solid wood beneath are easy to treat yourself. Extensive tunnelling in load-bearing timbers is a different matter — that needs a professional survey before any other decisions are made.
4. Choose the right treatment
For furniture and non-structural timber, a ready-to-use permethrin-based woodworm fluid is the standard choice. Products from timber treatment specialists such as Permagard, Cuprinol, or Ronseal are widely available. They penetrate the wood and kill larvae on contact.
For loft timbers and structural joists, you may want a stronger concentration. Always read the product label and use the correct dilution for the surface you are treating.
5. Prepare the area
Woodworm treatment fluid has a strong solvent smell. Open windows fully and keep the room well ventilated throughout. Remove soft furnishings, cover carpets and floors with dust sheets, and wear nitrile gloves and safety glasses.
If you are treating floor joists from below, a face mask is worth wearing too. Working in an enclosed under-floor space with solvent fumes is not pleasant.
6. Apply the treatment
Brush the fluid liberally onto all affected surfaces, working it into each exit hole. The idea is saturation — the liquid needs to penetrate deep enough to reach the larvae inside their tunnels.
Pay particular attention to end grain and any splits or cracks, which absorb treatment particularly well. Apply two coats if the wood is very porous, leaving 30 minutes between them. Do not miss the undersides of shelves, the backs of panels, or any hidden surfaces.
7. Leave to dry and ventilate
Most woodworm fluids dry in two to four hours, but the smell can linger considerably longer. Keep the area well ventilated for at least 24 hours. Do not put furnishings or bedding back in until the smell has fully gone.
The treatment continues working for months as it penetrates deeper into the timber. Any larvae that emerge through previously treated wood will be killed.
8. Fill the exit holes if needed
Once you are confident the treatment has worked and the infestation is dead, you can fill the holes with a wax filler pencil or fine wood filler if the appearance matters. On structural timbers, there is little reason to bother.
Monitor the area each spring for any fresh frass. A second treatment is rarely needed if the first was applied thoroughly, but it is always worth a check.
When to call a handyman
Call Richard if the infestation is widespread across loft timbers, floor joists, or structural beams, if the wood feels soft and spongy when probed, or if you are simply not sure what you are looking at. Misidentifying dry rot or wet rot as woodworm — and vice versa — is more common than people think, and they need completely different treatment.
Woodworm, damp, or timber problems?
The Sandwich Handyman can help identify the cause and advise on the right treatment, whether it is a straightforward woodworm job or something more involved like wet rot or rising damp.
Contact Richard