What is woodworm really and why does it attack wood?
At first glance, the word "woodworm" sounds like a single insect, one that burrows into wood and eats away at it. But no, it's a bit more complex. We're actually talking about several species of beetles whose larvae settle inside beams, furniture, or floors... and from there, they begin to bore holes inside, without anyone noticing.
Some of the best-known are the common woodworm (Anobium punctatum), the common woodworm (Lyctus brunneus), and the house capricorn (Hylotrupes bajulus). What's curious—and also worrying—is that they spend much of their lives hidden, digging tunnels in wood without leaving a visible trace.
It all begins when they lay eggs in small cracks or pores. Soon after, the larvae hatch, feeding on the softest part of the wood: the sapwood, rich in cellulose and sugars. And there they stay… for months or even years. When they emerge as adults, they leave behind those small, round or oval holes that are often the first clue that something is wrong. By then, of course, the damage can already be quite advanced.
Signs that your historic home may be in danger
You have to be vigilant. Especially if it's an old house, because the sooner woodworm is detected, the better the chances of avoiding major intervention. And how can you tell if there's activity?
- Exit holes appear, between 1 and 6 mm.
- A fine, sawdust-like dust forms just under beams or furniture.
- The wood weakens, to the point of breaking with simple pressure.
- In some cases, a faint ticking noise can be heard at night, especially in spring. This is the sound of the Xestobium rufovillosum.
Although it prefers damp places and soft woods, woodworm isn't particularly discriminating. And in historic homes, with structures that have stood the test of time for decades—or centuries—any imbalance in humidity or state of preservation can be a potential threat.
Environmental factors that favor woodworm
The environment plays a major role. If conditions are favorable, woodworms establish themselves and reproduce relentlessly. What benefits them most are:
- Relative humidity above 55 ºC. This helps the larvae survive.
- Untreated wood or wood with old varnishes that are already very worn.
- Closed and poorly ventilated spaces, such as attics, basements or false ceilings.
- Temperate temperatures, between 20 and 30 °C, which accelerate the entire process.
It's not about having a laboratory at home, but rather about controlling these variables as best as possible so as not to create a perfect breeding ground for pests.
Methods for diagnosing the presence of woodworm
You don't have to be a conservation expert to notice certain signs, although it can be helpful to know what to do. Some ways to tell if there's been recent activity:
- Vacuum the dust well and see if it reappears in the same places.
- Place paper or cloth over the holes. If they tear within a few days, that's a bad sign.
- Measure the moisture content of the wood. If it's too high, there's likely life inside.
- If you want to go further, there are tools such as resistography, which detect loss of density inside without having to open anything.
Woodworm prevention strategies
There's no mystery here: prevention is always better than cure. And in the case of woodworm, what can be done to prevent it isn't complicated or expensive.
- Maintain good ventilation throughout the house.
- If there is humidity, use dehumidifiers or improve air circulation.
- Carry out periodic checks of ceilings, beams and old furniture.
- Apply protective treatments that respect the original wood.
With these habits, the risk is significantly reduced, and you gain time to act if a problem ever arises.
Physical treatments to eliminate woodworm
When there's a confirmed infestation, intervention is necessary. In historic homes, physical methods are used whenever possible because they don't alter the original structure or materials.
Anoxia
A very effective technique is anoxia. Basically, it involves enclosing the pieces in airtight chambers and replacing the oxygen with nitrogen, until it drops below 0.1 %. Without oxygen, woodworms cannot survive. And best of all: the procedure is clean and doesn't damage the wood.
Heat treatment
Another option is controlled heat. The wood is heated to approximately 55°C for at least 16 hours. This eliminates the larvae without using chemicals. However, care must be taken to ensure the treatment doesn't affect the structure. Therefore, it is performed by specialized personnel.
Chemical treatments against woodworm
It's not always possible to apply heat or anoxia. In those cases, chemicals come into play. But when it comes to heritage, great care must be taken.
- Borates: they have low toxicity and also act against fungi.
- Permethrin and similar products: insecticides applied by spraying or injection. They last a long time, but are not always compatible with certain finishes.
This type of treatment should be performed by certified personnel, especially if the home is protected by law or contains valuable historical elements.
Techniques for repairing wood damaged by woodworm
Once the woodworm has been eliminated, the damage must be addressed. The important thing here is to preserve as much as possible without altering the essence of the home.
- Sometimes it is enough to graft new wood onto the affected area.
- In other cases, metal reinforcements are used, which remain hidden but reinforce the structure.
- Epoxy resins are also used, which consolidate without excessively modifying the original appearance.
Always with a clear principle: intervene just enough, without changing what is not necessary.
Heritage conservation and legal regulations
Many of these houses are protected by law. In Spain, for example, Law 16/1985 requires permission before carrying out any intervention on a Site of Cultural Interest. This includes everything from anti-woodworm treatments to replacing a beam.
That's why it's essential to have someone who knows the terrain well, both technically and legally.
We are a Structural Reinforcement Company in Mallorca
Dealing with woodworm in a historic home isn't just a matter of applying a product and that's it. It requires understanding the material, respecting its heritage value, and, above all, doing things right.
At Armalutx, we are specialists in structural reinforcements in Mallorca. We combine conservation experience with modern technical solutions tailored to each case. If you want to protect your home—and everything it represents—we can help. No rush, no improvisation, and always with care.
