If you have looked into woodworm treatment you will have come across boron, or boron-based products, alongside "water-based microemulsion insecticide". They are not competing versions of the same thing — they do different jobs, and which one is appropriate depends on the timber and the situation.
Here is a plain explanation of both.
Water-based microemulsion insecticide
This is what we use for the great majority of woodworm treatment.
What it is. An insecticide carried in a water-based microemulsion — meaning the active ingredient is dispersed in extremely fine droplets, which lets it penetrate the timber surface rather than sitting on top of it.
What it does. Two things. It kills the larvae currently active in the wood, and it leaves the treated surface protected, so beetles emerging or arriving later do not re-establish.
Why we favour it. It is low odour and non-flammable, which matters a great deal in practice. It means the property generally stays usable while the work happens — occupied houses, working buildings, a pub that needs to open. Older solvent-based treatments made a building uninhabitable for a period and carried a fire risk during application.
It is also environmentally sound compared with the solvent-carried products it replaced, which is why the industry moved.
Where it fits. Roof timbers, joists, floorboards, structural softwood — the everyday cases. This is what we used on the roof timbers at Dobbins Inn in Carrickfergus, a building around 800 years old that stayed open throughout.
Boron
What it is. Boron compounds — usually disodium octaborate — supplied as a paste, gel, rod or solution. A long-established timber preservative, effective against both wood boring insects and wood-destroying fungi.
What makes it different. Boron is water-diffusible. In damp timber it migrates with the moisture, travelling deeper into the wood over weeks rather than staying near the surface. That is genuinely useful in thick sections where a surface treatment cannot reach the middle.
Its dual action against both insects and fungi is also useful where you have beetle attack and rot in the same timber.
The catch. That same water-diffusibility means boron moves with water in both directions. In timber that gets wet repeatedly it can leach out over time. It is a preservative for timber that will be kept dry, not a solution for timber that stays wet.
Where it fits. Thick structural sections and beam ends, historic hardwood, and cases where fungal attack and insect attack coincide. Boron rods inserted into drilled holes in a damp beam end are a recognised technique for exactly that.
So which does your timber need?
For most domestic woodworm — common furniture beetle in roof or floor timbers — a water-based microemulsion applied properly is the right answer, and boron adds cost without adding much.
Boron earns its place in specific cases: deep sections where surface treatment cannot reach the core, historic hardwood where you want to retain the original timber rather than replace it, or combined insect-and-fungal attack.
Which is decided by the survey, not by the product. The survey establishes the species, the depth and extent of attack, the timber type and section, and — critically — the moisture. All four inform which treatment is appropriate.
The part that matters more than the chemical
No insecticide fixes a moisture problem.
Wood boring beetles need timber above a certain moisture content. Dry timber does not sustain most infestations. So an active infestation means something is keeping that wood damp: a leak, blocked ventilation under a floor, a failed damp proof course, condensation in a sealed-up roof space.
Treat the beetles, leave the damp, and you will be treating again. Every honest surveyor will tell you the same thing, and it is why our reports set out the cause and not just the treatment. It is also why the questions worth asking a contractor are about the moisture, not the product.
For the same reason, if the timber is soft and crumbling rather than holed, the issue is wet or dry rot rather than beetle attack — how dry rot occurs explains why moisture is the whole story there too.
What about DIY products?
You can buy woodworm fluids over the counter, and for a small, definitely-active, easily-accessible patch of infestation in dry timber they are not useless.
The limitations are worth being honest about. You cannot treat what you cannot reach, and most infestation is in timber under floors or in roof voids. Surface application to a painted or varnished floorboard achieves very little, because the coating stops penetration. And a shop-bought tin does nothing about whatever is keeping the timber damp.
If the affected timber is structural, or you cannot see all of it, that is the point to get it surveyed.
Getting it looked at
We have used and specified timber treatments across Northern Ireland since 1967, and manufacture our own fungicidal fluid from fully approved environmentally friendly chemicals. Properties we treated three decades ago have been reinspected with no sign of the woodworm returning.
Every survey comes with a written report. See woodworm treatment, find your local area, or ring 028 9061 8343.