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Consequences of Dampness in Homes - Wood Boring Insects

Updated: Mar 20

In our last article, we considered some of the common causes of penetrating dampness and how to identify it. In this article, we will look at the first of the two potentially costly consequences that damp issues can cause - wood boring insect attack.

woodworm timber

Wood boring insects are a group of insects that love to live and breed in timber, but not just any timber, damp timber. Whether it is structural timber or decorative furniture, these insects can cause significant damage if the wood is damp, or if the there are high humidity levels present. We will consider just three of these wood eating nasties;

Common Furniture Beetle

In the UK, the Common Furniture Beetle (also known as woodworm) is the most common, as the name would suggest. The adult beetles do not cause any damage themselves, but they lay eggs in damp or moist wood and their larvae spend the early part of their lives eating and tunnelling through the timber. These tunnels weaken the internal fabric of the wood, leaving it brittle & crumbly and can render structural timber elements useless. Once the larvae reach adulthood, they make their way to the surface of the wood and leave small round 'flight holes' of about 1-2 mm in diameter. These holes are often the first signs of an infestation. The Common Furniture Beetle prefers softwood, so will usually be the culprit behind damaged joists, rafters and floor boards, rather than hardwood furniture.

House Longhorn Beetle

The House Longhorn Beetle is another common wood boring insect found here in the UK. As these insects prefer hardwoods, they are more commonly found in older buildings where the structural timber elements are often made from oak. This beetle is larger than the Common Furniture Beetle and their tunnels and flight holes are larger also - from 6-10 mm in diameter. It is said that an infestation of House Longhorn Beetles can be heard eating through timber on warm days! Clearly, these larger holes can lead to more extensive damage and these insects should be dealt with as soon as they are encountered.

Deathwatch Beetle

The Deathwatch Beetle is another pest that likes to infest damp hardwood and is a constant threat to historic buildings due to their extensive use of oak & other European hardwoods. These insects are of a similar size to the Common Furniture Beetle with a similar size flight hole of approx. 1-2 mm. Like the House Longhorn, this beetle can often be heard before being seen. Adult beetles make a clicking sound by tapping their heads against the wood when communicating with other beetles and this can be particularly noticeable at night.


Getting rid of a wood boring insect infestation usually involves a combination of methods, depending on the extent of the problem. In a domestic setting, spraying of timber elements with an insecticide is usually sufficient to kill the insects that are present. In more severe infestations, sealing the area and fumigating is a more comprehensive approach. But treating the problem may only be effective for a time if the damp environmental conditions that caused the original infestation remain.


As always, prevention is better than cure. Importantly, a wood boring insect infestation can be avoided quite simply - by ensuring timber elements are kept dry, wood boring insects will only infest damp or moist timber.

Therefore, it is important to check structural timber elements periodically to see if the tell-tale flight holes are present. If an infestation has been treated in the past, try to see if new holes have appeared. Also look to see if fresh wood dust is present, either in the holes, or below them. This fine dust (called frass) is the wood dust that results from the larvae eating the wood as the make their way through it.

Unfortunately, the most 'at risk' timber is often is the most difficult to see, so ensure that basic precautionary measures are met. Fix any leaks promptly and keep external ground levels well below DPC level. Ventilation is key, especially below timber floors and in roof spaces. If necessary, add air bricks and eaves vents, these will increase the cross flow of air and help to keep the timber dry, even in areas that are hard to access.

Wood boring insects can cause significant problems to timber elements of your home if damp conditions are present. If these timber elements are structural, then rectifying the situation can also be quite costly. By trying to understand the signs of infestation, the causes and how to prevent them in the first place, you can protect your home from these destructive pests.

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