Category: Workshop Stories · Reading time: 7 minutes
A few months ago, I received a message with a photo and a single question: "Is this woodworm?"
It was the side of an inherited dresser. Eleven small, round holes, about the size of a ballpoint pen tip.
I replied with the same thing I always say: those holes don't tell me anything. What I need to see is what's underneath the furniture.
I asked her to place a white sheet of paper on the floor directly underneath it, and to leave the dresser untouched for a week. No moving it, no cleaning it, no touching it.
After seven days, she sent me the second photo. The paper was clean. That dresser had probably gone forty years without a single live insect inside, and she had spent two months not daring to put it in her daughter's bedroom.
The hole you see in an old piece of furniture is not where the insect entered. It's where it left. When the hole appears, that insect has already gone.
Woodworm doesn't bore to enter: it bores to exit
The cycle lasts for years, and absolutely nothing is visible from the outside.
The adult female doesn't drill anything. She lays her eggs in a crack, an open pore in the grain, or directly inside an old hole from a previous generation. From there, a tiny white larva, just a few millimeters long, emerges and burrows into the wood without leaving a visible mark.
And there it stays. Eating. For two to five years, depending on the humidity and temperature of the house.
All the damage is done by that larva, from the inside, while the surface remains impeccable. When it finishes, it transforms into an adult near the surface and bores its way out. That's the hole.
The adult lives for three or four weeks. It flies, reproduces, and dies. The emergence occurs mainly between May and August.
That's why holes are proof of an attack, but not of a current attack. They are a receipt, not an outstanding bill.
The white paper test: the only useful homemade test
What you need to look for is sawdust. An active infestation expels a very fine powder, almost like talc, which accumulates directly beneath the holes.
The test is done like this: thoroughly vacuum the area, clean the underside of the furniture, and place a white sheet of paper underneath. Leave it for a week without moving anything.
If new dust appears, there is activity. If the paper remains clean, you have a reasonable indication that the infestation has ceased.
Here's the weakness of the test: finding some sawdust isn't an automatic condemnation either. The tunnels in an old piece of furniture are full of old dust, and a vibration, a move, or a simple slamming door can cause it to fall out years after the last insect died.
That's why it's repeated. A clean sheet of paper in spring, which is when they emerge, is worth much more than any visual inspection.
Holes of 2 mm or 8 mm: it's not the same problem
Here it's worth looking closely, with raking light.
Round, 1 to 2 millimeters. This is the common furniture beetle, which mainly attacks the sapwood. Out of ten pieces that come into the workshop with holes, nine have this type. It's treated without drama.
Oval, 5 to 10 millimeters. These come from another family of insects, more associated with conifers and structural timber. In beams, it's serious. In a 19th-century walnut or oak piece of furniture, it's rare, and if it appears, it warrants a full inspection before buying anything.
The shape of the hole tells more than the quantity. A hundred round, inactive holes on the back of a wardrobe are part of that wood's biography. Three oval ones on a leg demand stopping and looking closely.
And yes: these holes are also one of the signs we use to date a piece, along with the joinery and hardware. I developed this fully in the 7 signs we look for in the workshop.
Why woodworm almost never thrives in a heated apartment
Larvae need wood with a certain amount of moisture. The wetter it is, the faster they develop. A city apartment, with heating in winter and dry air, is a bad place for them.
The pieces that arrive with real activity usually come from the same type of place: village houses closed for years, basements, unventilated storage rooms, garages with cold floors. It always comes down to the same thing: humidity.
This also explains why a treated piece placed in an inhabited house rarely causes problems again.
When you should NOT buy that piece of furniture
I'm saying this even if it makes things worse for all of us who sell antique furniture.
Do not buy it if there is fresh sawdust and the seller cannot tell you what treatment the piece has had or when it was done.
Do not buy it if the wood gives way to your thumb on a leg, a crossbar, or a structural side. If it sinks or releases dust when pressed, the damage is no longer aesthetic.
Do not buy it if someone boasts about having filled the holes. Filling doesn't kill anything, it just hides it.
Do not buy it if they tell you "that's from the period, it's nothing to worry about" without further explanation. It might be true. But ask what was done to the wood and when; if there's no answer, that phrase doesn't protect anything.
And now the other side, which also needs to be said: don't reject a good piece for having old, inactive holes. Those holes are part of what makes that wood impossible to manufacture today. Sanding them away destroys the patina and, with it, almost all the value of the piece.
What time does well, cannot be manufactured.
What we do in the Navalcarnero workshop
Each piece that comes in is reviewed before deciding whether to keep it.
Pieces from before the 20th century undergo anti-woodworm treatment: the wood is treated to eliminate any activity and is left free of woodworm before the finish is applied. For 20th-century, vintage pieces, the criteria are different, because their wood and origin are also different. I explained this when talking about the difference between antique and vintage.
The treatment is, by far, not the most expensive part of a restoration. I broke it down with real prices in how much it costs to restore an antique piece of furniture.
We only restore what we sell. We do not work on third-party pieces, and that's why we can stand behind every piece of furniture that leaves here.
More than 3,500 families have one at home, and the 4.9★ on Google and 225K+ followers on Instagram came from there.
Each piece arrives in the room of your choice, with shipping included throughout the peninsula.
How to prevent it from appearing in your home
- Do not store wooden furniture in unventilated storage rooms, basements, or garages.
- Ventilate closed rooms, especially guest rooms.
- Check the back and bottom once a year, where the wood is unfinished.
- Do not place wooden legs directly on damp floors.
- Be careful with what you bring in from the countryside: firewood, wicker baskets, old fruit crates.
None of these things take more than five minutes a year.
And if you now want a piece that has already been resolved
Everything we publish has passed through the workshop first.
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Frequently asked questions
How do I know if the woodworm is alive or if the attack is old?
You can tell by the sawdust. Clean the underside of the furniture, place a white sheet of paper underneath, and leave it for a week without moving anything. If fine dust appears, there is activity. The test is most reliable between May and August.
Can woodworm spread from one piece of furniture to another?
It can, because the adult flies and looks for wood to lay eggs. But it needs favorable conditions: moist wood and unfinished surfaces. In an inhabited, ventilated home with heating in winter, re-infestation is unlikely. The real risk is in storage rooms, basements, and houses closed for months.
Can woodworm be eliminated without damaging the furniture?
Yes, it's common practice in a workshop. Anti-woodworm treatment acts on the wood without altering its color or texture. What does destroy a piece is thoroughly sanding to remove the holes, because it eliminates the patina.
Does furniture with woodworm holes have less value?
It depends on two things: whether the infestation is still active and where the holes are located. Old, inactive holes on the back, side, or inside a drawer do not reduce value, and some buyers actively seek them out because they are part of the wood's history and proof that no one has sanded it to make it look new. What does reduce value, and quite significantly, is active damage or loss of strength in legs, crossbars, and any weight-bearing area. That's why the first thing checked in the workshop is not the number of holes, but whether there's anything alive inside.
