How can I tell if woodworm is still active?

Fresh, pale frass and clean-edged holes suggest activity. A practical home test is to clean the area thoroughly, note the date, and check again after the spring emergence season for new dust or new holes.

Do I need my whole loft treated?

Very rarely. Targeted treatment of demonstrably affected timbers, plus fixing the damp that made them attractive, is the proportionate response. Whole-property spraying is usually selling rather than surveying.

Will a mortgage lender insist on treatment?

Sometimes, if a valuer notes woodworm. A report establishing that the infestation is historic and inactive is often what settles it, and it is a good deal cheaper than treating timber that needs nothing.

Timber & Rot

Woodworm treatment

The first question is not how to treat it. It is whether anything is still alive in there.

Species identification and activity assessment first — a great deal of woodworm 'damage' is historic and long dead. Where it is active, targeted treatment of affected timbers.

Most of what people find is historic

The holes are exit holes. A beetle larva spends years inside the timber and the hole appears when the adult chews its way out and leaves. So a hole is evidence that something emerged — at some point, possibly decades ago. It is not evidence that anything is in there now.

This matters commercially, because a great many houses have old woodworm holes in floorboards from an infestation that died out generations ago when the building dried out. Treating those is spending money on a problem that resolved itself before you were born.

The tells for activity: fresh frass, which is clean and pale and accumulates below the holes rather than sitting greyed and settled; and holes with sharp, pale, unweathered edges. Confirming it usually means cleaning an area, then coming back and seeing whether new frass has appeared.

Species matters

Common furniture beetle is the usual culprit and is generally a manageable problem — small round holes around two millimetres, in sapwood, in damp-ish conditions.

Deathwatch beetle is a different proposition: larger holes, a preference for old damp hardwood, particularly oak, and slow but structurally serious damage in historic buildings. House longhorn beetle attacks softwood roof timbers and can do a great deal of structural harm relatively quickly, and it is regionally concentrated in parts of Surrey, which makes it directly relevant here.

So identification is not academic. It changes the urgency, the treatment and, with structural species, whether a timber engineer needs involving at all.

Treating a live infestation

Reduce the moisture, because most wood-boring insects need timber damper than a well-ventilated building provides. Improving subfloor ventilation and fixing whatever is wetting the timber is a large part of the answer and is frequently overlooked in favour of chemicals.

Then targeted application of an appropriate preservative to the affected timbers, rather than blanket-spraying an entire roof space on principle. Where structural strength has been compromised, the affected timber is replaced or reinforced — a chemical treatment kills the insects but does not restore a weakened joist.

Common questions

How can I tell if woodworm is still active?: Fresh, pale frass and clean-edged holes suggest activity. A practical home test is to clean the area thoroughly, note the date, and check again after the spring emergence season for new dust or new holes.
Do I need my whole loft treated?: Very rarely. Targeted treatment of demonstrably affected timbers, plus fixing the damp that made them attractive, is the proportionate response. Whole-property spraying is usually selling rather than surveying.
Will a mortgage lender insist on treatment?: Sometimes, if a valuer notes woodworm. A report establishing that the infestation is historic and inactive is often what settles it, and it is a good deal cheaper than treating timber that needs nothing.