Treatment Methods
Insecticidal Spray Treatment
A water-based permethrin spray is the standard professional treatment for active common furniture beetle in accessible timber. Low odour, touch-dry in hours, and applied to bare joists, rafters and floorboards.
- Water-based permethrin — low odour, occupied-home safe
- Touch-dry in a few hours, most homes treated in a day
- Backed by a 30-year guarantee on treated timber
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The standard treatment
What woodworm treatment spray actually does
Insecticidal spray is the method most people picture when they think of woodworm treatment, and for good reason — it is the right answer for the most common situation. Where the common furniture beetle (Anobium punctatum) is active in accessible softwood, a water-based permethrin spray applied to bare timber is effective, fast and minimally disruptive. The beetle responsible for roughly three quarters of UK infestations leaves neat 1–2mm exit holes and has a three-to-four-year life cycle, so the goal is to treat the timber surface where larvae feed and to kill the adults as they emerge.
Spray is not the answer to every problem. It is a surface and near-surface treatment, so deep structural timber, damp joist ends and buried sections are better suited to a boron gel or paste. A free survey always comes first to confirm the species, check the infestation is active, and decide whether spray is the right tool.
Water-based permethrin
A modern, low-odour insecticide
Permethrin is a synthetic pyrethroid — a well-established insecticide used in professional timber treatment for decades. The key difference today is the carrier: modern formulations are water-based rather than solvent-based, which means far less smell, lower flammability and a product that is suitable for occupied homes.
Applied to bare timber, the permethrin remains in the surface layers of the wood. Adult beetles emerging through it, and larvae feeding close to the surface, are killed. Because it stays in the timber, it also gives a residual protective effect against reinfestation — one reason treated timber can carry a long guarantee.
Why professionals favour it
- Low odour and low flammability compared with solvent sprays
- Safe for occupied homes once touch-dry and ventilated
- Leaves a residual protective layer in the timber surface
- Effective against the common furniture beetle in softwood
- Quick to apply — most homes are treated in a single day
How it is applied
From bare timber to touch-dry in a day
Spray works best on accessible, exposed timber. The application itself is straightforward, and the disruption is modest.
Prepare and clear the timber
Affected areas — joists, rafters, the undersides of floorboards — are cleared of stored items, loose debris and old bore dust so the spray reaches bare wood. Heavily lagged or boxed-in timber is exposed where practical.
Apply the permethrin spray
A low-pressure water-based permethrin spray is applied evenly to all accessible timber surfaces, working the product into joints, end grain and the worst-affected sections where larvae feed nearest the surface.
Allow to dry and ventilate
The treated timber is left to dry. It is touch-dry within a few hours, and once the space has ventilated the area is safe to return to — most homes are back to normal use the same day.
Penetration, drying & safety
What to expect during and after
Surface penetration
Spray treats the surface and the layers just below it. That is exactly where it needs to be for the common furniture beetle, whose larvae feed close to the surface and whose adults must pass through the outer timber to emerge. For thick structural sections or timber you cannot reach all sides of, a deeper-diffusing boron paste is the better choice — which is why surveyors sometimes combine the two.
Drying and touch-dry times
Treated timber is typically touch-dry within a few hours. Floors can usually be walked on and rooms reoccupied the same day, once the area has been ventilated. We will give you clear, room-by-room guidance on timings before we leave.
Safety and ventilation
While the spray dries, keep people and pets out of the treated room and open windows to ventilate. Fish tanks should be covered and their pumps switched off during application, as permethrin is harmful to fish and other aquatic life. Once dry and aired, the timber is safe to live with. All products are applied in line with UK and HSE guidance, and we follow Property Care Association standards. If your work is in a roof space, remember that bats are legally protected and a bat check may be needed before treatment.
When spray is the right choice
- Active common furniture beetle in accessible softwood
- Open floor joists, exposed roof rafters and floorboard undersides
- Sound timber that has not lost structural strength
- Whole roof spaces and sub-floor voids you can get into
When another method is better
- Damp joist ends bedded into masonry — use boron paste
- Heavy structural beams — paste diffuses deeper than spray
- Timber weakened beyond the surface — structural repair
- Boxed-in or buried timber you cannot expose to spray
Thinking about treating it yourself first? Our guide to the best woodworm treatment products covers the DIY permethrin and boron sprays sold in the UK, what they do well and where they fall short.
Keep reading
Boron Gel & Paste
Deep-penetrating treatment for joist ends and structural timber.
Learn more →Woodworm Treatment
The full overview of surveyed, guaranteed woodworm treatment.
Learn more →Woodworm Survey
How a free survey confirms the species and decides the method.
Learn more →Best Treatment Products
DIY permethrin and boron sprays reviewed for 2026.
Learn more →All Treatment Methods
Spray, boron paste, fumigation and structural repair compared.
Learn more →Woodworm Treatment Cost
What spray and other methods cost by room and whole house.
Learn more →Frequently asked questions
What chemical is used in woodworm treatment spray?
Is woodworm spray safe for my family and pets?
How deep does insecticidal spray penetrate the wood?
When is spray the right choice over other methods?
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