Best Woodworm Treatments UK 2026 — Sprays, Fluids & Injectors

Holes in timber are the end of the story, not the start of it. The Natural History Museum on the common furniture beetle: “The larvae bore straight into the wood making a hole indiscernible to the naked eye.” (Natural History Museum). The hole you can see is where an adult left.

Old Holes or an Active Outbreak

The Society for the Protection of Ancient Buildings gives the test: “Active outbreaks are identified by holes with sharp rather than round edges, and the interiors and bore dust ('frass') are not dark but the colour of freshly-cut timber.” (SPAB). For the common furniture beetle it adds the size: “Furniture beetles target both softwoods and hardwoods, producing 1-2 mm wide holes and lemon-shaped frass.”

The Natural History Museum describes the same evidence from the insect’s side — “small piles of wood dust (frass) characteristic of woodworm damage” — and the timescale: “Full-grown larvae change into pupae and, after 6-8 weeks, into adult beetles.” Fresh, pale frass under a sharp-edged hole is the sign that decides whether anything on this page is needed.

The Legal Position on Wood Preservatives

A woodworm treatment is a biocide. HSE’s guidance on using them: “If you are a member of the public, you should only use biocidal products that are intended for the general public - sometimes the terms 'amateur' or 'non-professional' might be used instead.” (HSE). And: “members of the general public must not use professional or industrial use products”. The label on the container states which a product is; the listings here do not.

HSE on the label itself: “Following the label instructions carefully should be enough to allow the product to be used safely and effectively.”

Where a Treatment Does Not Help

Where the timber is damp. SPAB: “Wood-boring insects, like timber-decaying fungi, only establish themselves where dampness exists.” And on what a chemical is for: “Action could entail targeted chemical treatment - but not as a substitute for promoting drying, or general precaution for extinct or non-existent outbreaks merely to obtain a guarantee.”

Where the outbreak is old. The same sentence covers it: a treatment applied to extinct holes is a precaution SPAB says not to take for its own sake.

Where a meter is read as a verdict. SPAB on the fifth product’s class: “However, over-reliance should not be placed on surface readings from electrical moisture meters.” A reading is a reading, not a diagnosis.

What Decides the Choice

1. Whether the outbreak is active

SPAB’s test above. If the holes are round-edged and the frass is dark, SPAB’s advice is not to treat merely to obtain a guarantee.

2. Whether the listing names an active substance

Both Rentokil listings state permethrin. The Barrettine listing claims what it kills and names no substance. The Woodwyse listing carries no bullets at all. What is in the first two is on the page; what is in the other two is on the container.

3. How it is applied, as listed

A 1-litre fluid and a concentrate that makes 25 litres are brushed or sprayed over an area. The 300ml aerosol and the 250ml injector bottle are for holes and small areas. The meter treats nothing and is listed for wood from 6-44%.

If a Treatment Is Not the Answer

Dry the timber. SPAB puts it before any chemical: “Good preventative maintenance and moisture monitoring can avert dampness and, therefore, ensuing damage caused by wood-borers.”

Confirm it is active before you buy anything. Sharp edges and pale frass, per SPAB. Old holes need no treatment.

Get a specialist in for structural timber. HSE: “If you are not a professional, consider using a professional pest controller to deal with the problem.”

Using Them

1. Establish the outbreak is active. Sharp-edged holes, frass the colour of fresh-cut timber.
2. Deal with the damp first. Chemical treatment is not a substitute for drying, per SPAB.
3. Read the container, not the listing. Two of the four treatments name no active substance online.
4. Match the product to the area. Fluid or concentrate for joists and boards; aerosol or injector for holes.
5. Treat a meter reading as one reading. SPAB’s caution above.

The Five Products Compared

Every column below is what the Amazon listing itself states. Where a listing does not state something, the cell says so rather than guessing.