Can you have a wasp or hornet nest in your siding?

Contents

• Determine whether there is a nest behind your exterior siding

• The Risks Posed by a Hornet or Wasp Colony to Your Home

• How to Safely Remove a Nest from Siding

• Conclusion

Yes. In fact, it’s one of the favorite spots for wasps and hornets in Belgium. Cladding provides the perfect shelter: dry, dark, well-ventilated, protected from the wind and predators, with an air gap between the cladding and the wall that offers several cubic meters of space. You couldn’t design a better home for a colony if you tried.

Things to remember

• Beyond simply identifying them, this article explores the structural and health hazards specific to nests hidden behind siding

• We highlight Frelons' expertise

• be to treat these complex infestations, particularly the Asian hornet, without damaging the insulation

• Determine whether there is a nest behind your exterior siding

The problem is that these nests remain hidden for weeks. A queen settles in during April, nobody notices a thing, and by August you have three hundred workers coming in and out through an 8-millimeter gap under a board. By this point, the nest has already made itself at home in your exterior insulation.

At Frelons.be, we handle these types of situations year-round, including in the winter when it comes to locating abandoned nests or treating queen wasps in the spring. Nests behind siding are among the most technically challenging to treat, because you can’t see what you’re treating. Here’s how to spot them, how much they might cost you, and, most importantly, what you should absolutely avoid doing.

Determine whether there is a nest behind your exterior siding

It all starts with an ordinary observation: insects circling the same spot on the facade. Not at random, not just passing by. Always at the same spot. That’s the number one sign.

To spot a hidden nest, sit in your garden on a nice day, between 11 a.m. and 4 p.m., and watch your siding for ten minutes. If a colony has settled there, you’ll see insects making regular, almost mechanical back-and-forth trips: a wasp flies out, heads straight for the garden, and another returns and disappears into the same crack. At a mature nest, you can count ten to thirty trips per minute. With Asian hornets, the flight is heavier and noisier, and they often return in a nosedive, hesitating briefly in front of the entrance.

The second clue is the sound. Press your ear (from a reasonable distance, of course) against the interior wall corresponding to the suspicious area. A continuous scratching sound, like sandpaper being rubbed gently, or a low hum that rises and falls: these are the workers chewing on the wood and spreading the paper pulp to expand the nest. Many people describe this as «sand flowing through the wall.» At night, when the house is quiet, it’s even more noticeable.

The third clue is the traces. Look at the bottom of the facade and the ground just below the entry point. You’ll often find fine wood particles there—light gray shavings—and sometimes brownish stains on the wood siding. These streaks are the colony’s waste and moisture escaping. On light-colored siding, they’re very easy to spot.

Be careful not to confuse them. Not all insects that enter a building’s exterior build paper nests. Mason bees seal small holes with dirt; these are the famous mud cocoons found in masonry joints or screw holes: they’re solitary, harmless, and protected—leave them alone. Chickadees and sparrows also like to nest behind siding, but their comings and goings are sporadic—they carry twigs or moss in their beaks—and the sound they make is like chirping. It’s nothing like the constant scratching of a colony.

A wasp nest in the siding can also be identified by its seasonal pattern: none in April, barely noticeable in June, and teeming in August and September. If activity spikes in late summer, you’re dealing with a colony, not just passing insects. And if you see large brown and yellow insects with yellow legs and a black thorax, call us: they’re Asian hornets.

The Risks Posed by a Hornet or Wasp Colony to Your Home

The property damage is widely underestimated. A mature common wasp nest can grow to the size of a basketball—sometimes even a beach ball. A secondary Asian giant hornet nest can exceed 70 cm in diameter. In a 4- to 6-cm cavity behind the siding, the colony has only one option: to push outward. It crushes the rock wool, compresses the rain screen, and warps the exterior insulation panels. I’ve seen wooden siding boards literally peeled off their battens by the pressure of the nest.

Then there’s the humidity. An active colony produces large amounts of water vapor—from the respiration of several hundred individuals and the moist wood pulp they constantly spread. This moisture gets trapped in the air gap, right where your rain screen is supposed to stay dry. The result: water-saturated insulation, declining thermal performance, and—on wood—an ideal breeding ground for wood-destroying fungi. This is the kind of damage you discover three years later when you tear down the facade, by which time the mold has already attacked the framing.

An abandoned nest isn’t harmless either. Wasps never reuse it, but the papier-mâché remains there, soaking up water and attracting moths, dermestid beetles, and spiders. And a 40-centimeter-long carcass wedged behind a board blocks the lower ventilation of the siding. Your facade can no longer breathe properly.

Now, the health hazard. A wasp defends its nest within a radius of 3 to 5 meters. The Asian hornet, on the other hand, considers a 5-meter zone around its entrance to be its territory and attacks in swarms. The danger posed by the Asian giant hornet does not come from its venom—which is no more toxic than that of a wasp—but from the number of stings and the length of its stinger, which can penetrate thick clothing. When the nest is in exterior siding, the entrance is often at eye level, near a door, a patio, or a bedroom window. You walk past it ten times a day without even realizing it.

The worst-case scenario involves a lawn mower or a ladder. A vibration on the facade, a blast from a pressure washer on the siding—and you trigger a massive defensive reaction. We’ve had to respond to incidents triggered by something as simple as sanding a shutter two meters from the nest. For someone with allergies—or a child—five to ten stings are enough to send them to the emergency room.

And then there’s the inside. Wasps often end up getting in. A poorly sealed window joint, an electrical conduit, a ventilation hatch—they’ll find a way in, and before you know it, you’ll have worker wasps in the upstairs bedroom. This isn’t rare at all; in fact, it’s a common reason for service calls in late summer.

How to Safely Remove a Nest from Siding

Rule number one—and I’m going to repeat it because this is the mistake that results in the most emergency interventions: Don't cover the hole. Never. No expanding foam, no silicone, no cloth, and no tape. Don't block the hole—that's the absolute rule.

Why? Because a trapped colony doesn’t die. It burrows. The wasps gnaw through soft wood, drywall, and membranes, looking for a way out. In 8 out of 10 cases, that exit leads deeper into the house. We’ve already had to respond to calls from people who sealed off an entrance on Saturday and found two hundred wasps in their bathroom by Tuesday. The same goes for over-the-counter insecticides sprayed into the crack: you kill fifty workers, you agitate the other thousand, and you force the nest to open a second entrance somewhere else.

The second thing to keep in mind: removing the siding. Many homeowners assume that all they need to do is unscrew two cladding panels to access the nest. But when you remove the panel, you’re essentially opening the nest wide—with your arm outstretched while standing on a ladder. The colony pours out by the hundreds. This is exactly the kind of situation where serious accidents happen.

The proper method—the one used for this type of nest in the siding—is based on three principles. We work through the existing opening without dismantling anything. We use a telescopic pole equipped with an injection tube that delivers a highly volatile insecticide powder deep into the heart of the colony, through the air gap. And we act at the right time: early in the morning or in the evening, when all the workers have returned to the nest, to treat the entire colony at once.

The powder has a major advantage over liquid aerosols: it disperses into the building’s cavity, sticks to the worker ants’ legs, and spreads throughout the nest by contact. The nest is completely destroyed within 24 to 48 hours, without any damage to the insulation, rain screen, or siding. There are no visible traces left on the facade. For stained wood siding or fiber-cement siding, that makes a difference.

When it comes to the Asian hornet, the approach is a little different. A secondary nest built into a building’s exterior often requires a specific product and full protective gear, because these insects swarm out at the slightest vibration. Professional intervention using an approved protective suit is not a luxury: DIY protective suits cannot withstand the sting of an Asian hornet. And you should never work alone on this type of nest.

After treatment? Leave the carcass in place for a few weeks if it’s inaccessible; it’s not dangerous once the colony is dead. If the nest is large and obstructs ventilation behind the siding, arrange for its removal by carefully dismantling one or two panels—while the structure is cool—without any risk. This is a good time to check the condition of the insulation and seal off any entry points. A rodent-proof screen at the bottom of the siding, resealed joints, and a few millimeters of adjustment—and the facade will be airtight again for the next season.

Pest control for a building facade isn't about using harsh chemicals. It's about identification, timing, and the right equipment.

Conclusion

A wasp or hornet nest in siding is nothing out of the ordinary—in fact, it’s one of the most common scenarios we deal with. What makes all the difference is how you react. Watching them come and go, listening for scratching noises, locating the entry point: fine. Sealing it up, spraying it, or tearing it down: never.

The longer you wait, the larger the colony grows, and the more expensive the damage to the exterior insulation becomes. Treating a nest in June takes just twenty minutes. The same nest in September turns into a major repair job involving moisture damage behind the walls.

Do you see insects crawling into your building’s exterior? Call Frelons.be. We provide year-round service for both facade pests and Asian hornet nests, using equipment that treats the nest without damaging your siding. Just give us a call or send a photo, and we’ll tell you right away what you’re dealing with.

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