15 49.0138 8.38624 1 0 4000 1 http://georgiancottage.co.uk 300 0

Woodworm! But how do I tell if it’s still active?

1 Comment

Woodworm. The signs of it are pretty obvious. Holes in your wooden furniture, floorboards and roof space. But what is woodworm, and if you’ve got it how do you know whether it’s inactive or if the exit holes that you can see are part of an ongoing woodworm infestation?

Woodworm is the general name given to the wood-eating larvae of various beetles that infest houses and furniture. The adult female beetle lays her eggs in an environment which will offer the best chances of survival for her offspring, which means moist sapwood: the outer living part of the tree.

As a result, the majority of woodworm damage is confined to the sapwood at the edges of floorboards and joists, and may not cause significant damage or weakening of timbers in the short term. However, generation upon generation of woodworm will cause structural damage to the fabric of a house if they are left to their own devices and will greatly reduce the strength of the infected wood.

Another drawback is that infestations can often go unseen, as the main damage is caused inside the timber before adult beetles emerge from the wood.

Types of Woodworm

Common Furniture Beetle

common furniture beetle

Common furniture beetle attacks a variety of timbers, including the sapwood of hardwoods, softwoods, plywood and wattling. This beetle damages wood by tunneling along the grain. Tunnels are relatively short and contain a loose bore dust.

As the name suggests, common Furniture Beetle is the most common species of woodworm found in the UK.

House Longhorn Beetle


The house longhorn beetle attacks the sapwood of seasoned softwood, causing damage by tunneling in sapwood, which can lead to structural collapse. House longhorn exit holes are oval not round and will be full of frass (beetle excrement)

Deathwatch Beetle


Deathwatch Beetle attacks the sapwood and the heartwood of hardwoods, usually oak, which have partly decayed. If you have a deathwatch beetle infestation then it could be a major problem as they tend to create extensive tunneling networks towards the centre of the timber. This beetle rarely attacks softwoods.

Exit holes are round and 3mm diameter. Bore dust is bun-shaped and contains pellets visible to the naked eye.

Deathwatch Beetle damage is often more extensive than initially expected from its external appearance.

Powder Post Beetle


The powder post beetle only attacks the sapwood of seasoned wide-pored hardwoods with a high starch content. If the timber is over 15 years old then the powder post beetle won’t touch it.

You’re unlikely to find this beetle in your average domestic environment and it’s usually more of a problem in timber yards or furniture factories.

The Signs of an Active Woodworm Infestation

Fresh Exit Holes In Timber

Round or oval shaped with sharp edges, the holes will appear clean and fresh.

Tunnels In The Wood

Also known as ‘galleries’, which are often hard to see.

Bore Dust

Also known as frass, caused by the emerging adult beetles and made up of wood dust and their excrement. Frass is usually visible below the infested timber and when in loft spaces it can be seen in caught in spider webs.

Weak And Damaged Floorboards

Jump up and down on your floorboards, if they are springy and have no external signs of holes, then they are fine. In extreme cases, a foot or chair leg going through the floor can indicate a more serious problem.

Crumbling Wood

Look around the corners or edges of roof joists or floorboards.

Dead Beetles

Usually found near the infested timber or around nearby windowsills.

Adult Beetles

They emerge from timbers between May and October and head towards light places, so look for them on white windowsills and on your bathroom suite.

Woodworm Larvae

These are usually a creamy-white colour and tend to be curved in shape.

Even if you have some of these signs, if you don’t see the live beetles it could still be an inactive and old infestation.If you suspect a woodworm infestation, you can take any of the four following actions:

  • Do nothing and monitor the infested timber closely for signs of emergence and activity during the flight season between May and October.
  • Get a detailed woodworm survey from a reputable company. I’m not sure about free surveys, as I can only see one way in which they can make money this way: by then selling you woodworm treatments that you may not really need.
  • Investigate the past history of the house to see whether it has any guarantees in place or invoices for treatment.
  • Carry out precautionary treatment to make sure that any potential future emergence is stopped in its tracks. A treatment usually carries a 10 year guarantee, but in practice it can be effective for 20 to 30 years.

The Georgian Cottage Woodworm Survey

After having a structural survey carried out before we bought the cottage, which flagged up woodworm, we’ve now just had a comprehensive timber survey carried out, using Brick Tie Preservation.

Their guy, Mike, came in and made a thorough inspection of the property, surveying the loft space, lifting carpets throughout the property and checking the top surface and under the stairs, as well as taking damp readings and checking around the exterior of the house at the state of the air bricks.

The 10 page survey was available in just a few days and went into a lot of detail, with the final assessment being that the woodworm infestations in the cottage are old and likely to be inactive.

Common furniture beetle was identified as the culprit, with various generations of infestation having come and gone over the 200 years that the cottage has been standing.


As the survey was carried out in January – outside the flight season of the common furniture beetle – there is still a slim chance that there could be a current infestation. Visible insect infestation is rare in January, as the woodworm will be in the grub stage of its lifecycle, when the insect is hidden and feeding within the timber.


However, in most cases, the woodworm holes appeared very dirty and old, so are unlikely to be from a recent infestation.

Based on the evidence that was presented to me by Brick Tie Preservation, I decided to monitor the situation, rather than go for a treatment.

I did this by taking sections of wood under the stairs and in the loft that had signs of woodworm activity, inking the holes with a permanent marker and adding the date.


I’ll keep checking these sections of wood to see whether any fresh holes appear. If they do, I’ll be calling Brick Tie Preservation to carry out a chemical treatment. For the loft, I’ll remove all the insulation materials then have them come in to defrass the space (removing decayed and damaged timber by hand), brush down the surface timbers and clean the sections between the ceiling joists. From there, it’s a case of them providing suitable protection to the water storage tank and spraying all the accessible roof timbers using preservative fluids.


I’ll let you know how I get on with monitoring the situation.

Did You Find This Post Useful?

Have you experienced woodworm? Let me know how you got on, I’d love to hear from you. Get in touch and tell me your story.


1 Comment

  • January 24, 2016 at 2:31 pm

    I’m glad you found Mike’s advice useful. Now you’re a client you can call us for free advice on any aspect of the work you propose in the future. Best wishes for a successful project.


Leave a Reply