If you've had a timber survey done recently, you may have heard your surveyor mention a "microemulsion" treatment or a "boron" treatment, sometimes in the same conversation. They're often confused with each other, but they're actually used to solve two quite different problems: one targets active woodworm, the other targets dry rot. Here's the distinction, in plain terms.
Microemulsion treatments: for woodworm
A microemulsion is a concentrate that's mixed with a carrying agent rather than used as a solvent-based product. Breaking the active insecticide down into extremely fine droplets means it disperses evenly through the carrying agent and penetrates timber effectively, offering a different set of handling characteristics to oil- or solvent-based formulations.
Compared to traditional woodworm treatments, this approach generally offers:
Low odour during and after application
Faster drying and quicker reoccupation of treated areas
Good penetration into timber, reaching larvae within the wood rather than just coating the surface
A lower toxicity profile, making it more suitable for use in occupied homes, roof spaces, and floor voids
This is the treatment used where the problem is active wood-boring insects — flight holes, frass, or larvae found during a survey.
Boron treatments: for dry rot
Dry rot is a different problem entirely — a fungal decay that can spread through masonry as well as timber, and needs a different chemical approach to arrest it. Boron-based concentrates are the standard tool here.
Boron compounds work by being highly effective against fungal decay while remaining soluble in their carrying agent, allowing them to move through damp or affected timber and reach the fungal growth rather than just sitting on the surface. Because dry rot can travel beyond the visibly affected timber, treatment often needs to extend into surrounding masonry and adjacent timbers, not just the section that looks damaged.
It's worth being clear that boron treatment isn't a standalone fix. The moisture source causing the dry rot has to be identified and stopped first, and any structurally affected timber needs to be cut out and removed, before treatment is carried out. Applying a fungicidal treatment without addressing the moisture and removing the decayed timber won't resolve the underlying problem.
Dual-purpose treatments: when both are combined
There's also a third category worth knowing about: dual-purpose concentrates that combine an insecticide and a fungicide in a single microemulsion formulation. These are designed for situations where a timber has both an active woodworm infestation and early-stage fungal decay (wet rot or dry rot) in the same area, so a single application can address both rather than treating in two separate passes.
These combined products carry the same handling benefits as the insecticide-only microemulsions — low odour, good penetration, quick turnaround — while adding the fungicidal action normally associated with boron-based treatments.
They're not a universal substitute for the boron-based approach, though. Where dry rot has spread into masonry, or where mycelium has travelled well beyond the visibly affected timber, a proper boron treatment extending into the surrounding structure is still the more thorough option. Dual-purpose products are best suited to timber-only situations where both problems are present but contained.
Why the distinction matters
It's worth understanding which treatment is actually needed, because they're not interchangeable:
A woodworm-only property doesn't need boron/fungicidal treatment
Active dry rot needs a fungicidal (boron-based) approach, not an insecticide
Some properties have both problems and need both treatments, applied to different areas
A proper survey should identify which of these you're actually dealing with before any treatment is proposed. If your surveyor is recommending both, ask why — it should be because both problems are present, not as a blanket precaution.
This post is for general information. If you're concerned about woodworm or dry rot in your property, a proper survey is the only way to know what treatment, if any, is actually needed.