How to Spot Woodworm and When to Worry

Few things worry a homeowner quite like a scattering of tiny holes in a floorboard or roof timber. Woodworm has a fearsome reputation, and it is true that left unchecked it can weaken timber. But in a lot of Hampshire homes, especially older ones, the holes you find are the remains of an infestation that died out years ago. Here is how to tell the difference, what to look for, and when it is worth getting someone in.

What woodworm actually is

Woodworm is not a worm at all. It is the larval stage of several wood-boring beetles. The adult beetle lays eggs in cracks and end grain, the larvae hatch and tunnel through the timber for anything from a couple of years to several, feeding as they go, and then they bore their way out as adults. The round holes you see are exit holes, so by the time they appear, that particular generation has already left.

In the UK the most common culprit by far is the common furniture beetle. It favours softwood and the sapwood of hardwoods, so floorboards, joists, roof timbers and old furniture are all fair game. Other species turn up less often: the deathwatch beetle prefers old, damp hardwood such as oak in period buildings, and wood-boring weevils tend to follow wet rot rather than cause the problem themselves.

Signs to look for

Most woodworm is found during other work, when a carpet comes up or someone goes into the loft. These are the signs worth checking for:

• Small round exit holes, typically 1-2mm across for common furniture beetle, often in clusters
• Fine, gritty dust (called frass) below the holes or spilling out of them
• Holes with clean, light-coloured edges rather than dark, dirty ones
• Timber that feels soft or crumbles when you press a screwdriver into it
• Adult beetles near windows or on sills, usually between late spring and late summer

Under floors, along the edges of loft boards and in cupboards under the stairs are the usual places to find it, because these spots tend to be cooler, less disturbed and sometimes damper than the rest of the house.

Active or historic: when to worry

This is the key question, and it is where a lot of unnecessary worry and spending comes from. An infestation that finished decades ago does no further harm. The tell-tale signs of activity are fresh frass, holes with crisp pale edges, and new holes appearing over time. Old holes usually look dark and dusty inside, with no fresh powder around them.

A simple check is to vacuum the area clean, or cover a few holes with masking tape, and look again after the next summer emergence season. If new holes or fresh dust appear, something is still going on. If nothing changes, you are most likely looking at old damage.

Moisture matters a great deal. Wood-boring beetles prefer damp timber, and modern central heating dries most living spaces out enough that infestations often die off on their own. That is why active woodworm tends to show up where there is a damp problem: a leaking roof, poor sub-floor ventilation, blocked air bricks or a bridged damp-proof course. Fix the damp and you remove the conditions the beetles need.

If you think you have an active infestation, or timber looks badly affected, it is sensible to have it looked at properly. For treatment itself, a specialist timber surveyor or pest control firm is the right call, ideally one belonging to a recognised trade body such as the Property Care Association. Where the timber has been weakened, that is where our repairs and maintenance service comes in.

Repairing timber damaged by woodworm

Surface holes in a floorboard or skirting are usually cosmetic. Structural timber is a different matter. If a joist, rafter or stair tread has been heavily tunnelled, it can lose strength, and that needs assessing by someone who knows what they are looking at.

Depending on how far the damage goes, the options are broadly:

• Leaving sound timber in place once the infestation is confirmed as dead
• Cutting out a damaged section and splicing in new timber
• Sistering a new joist or rafter alongside a weakened one to share the load
• Replacing individual floorboards, treads or lengths of skirting outright

In period homes we generally try to keep as much original timber as possible, replacing only what has genuinely failed. Our guide to repairing versus replacing carpentry goes into how we make that call, and if your floors are older boards worth saving, restoring Victorian floorboards covers what is involved. Every job differs, so a look in person is always the best starting point.

Get a carpenter's opinion

If you have found holes in your floors, loft or staircase and are not sure whether they matter, we are happy to take a look. We can tell you whether the timber is sound, whether damp is part of the picture, and what any repair would involve, without trying to sell you work you do not need. See our repairs and maintenance service or get in touch for a free, no-obligation quote anywhere across Hampshire.