Dealing with wasps right now? Wasp Nest Removal, by a team that does nothing else.
Cavity nests are common and they behave differently to a nest hanging in a loft or a shed. You cannot see the nest, you cannot judge its size, and the only access anyone has to it is the gap the wasps are flying through. That shapes everything about how it gets dealt with.
How to tell there is a nest in the wall
- A traffic line. The clearest sign. Wasps arriving and leaving steadily through one point, following roughly the same flight path in and out. Watch it for a minute on a warm afternoon and the pattern is obvious.
- The entry point. Usually an air brick, a weep vent between bricks, a gap where a pipe or cable passes through, a crack in mortar, or the join under a window sill.
- Sound. A faint rustling or scratching inside the wall on a quiet evening, sometimes mistaken for mice. Wasp noise is a dry papery rustle rather than scampering.
- Wasps indoors. Repeatedly finding wasps in one upstairs room, particularly around a light fitting or a chimney breast, often means the colony is in the cavity next to it.
- Staining. Occasionally a damp patch or brown staining on internal plaster where a large nest has built up moisture against the inner leaf.
Why blocking the hole is the mistake to avoid
It is the most common thing people try and it reliably makes the situation worse. A wasp colony that finds its exit sealed does not give up and die. It chews. The material it chews through is whatever is softest and nearest, and in a cavity wall the outer leaf is brick while the inner leaf is often plasterboard, old lath or perished mortar.
The result is a colony that arrives in the bedroom rather than the garden. We attend this several times every season, and it is always a bigger and more distressing job than the original nest would have been.
The same logic applies to foam, expanding filler and tape. Seal the route only after the colony is dead, never while it is active.
Why aerosols usually fail on a cavity nest
Shop-bought wasp sprays are designed for a nest you can see and reach. A cavity nest may sit a metre or more inside the wall, offset from the entry hole and hidden behind insulation. A spray fired into the gap treats the entrance and little else.
What it does achieve is provoking the colony. Wasps release an alarm signal when the nest is disturbed, which brings the rest of the colony out through the only exit they have, towards whoever is standing at it. If you are on a ladder at the time, the retreat is the dangerous part rather than the stings. We would ask you not to try it.
How a cavity nest is treated properly
- Confirm the entry point. The visible hole is not always the one in use, and larger colonies sometimes have more than one. Watching the traffic identifies the live route.
- Treat at the entrance. A professional product is applied at the entry point so that returning wasps carry it inside to the nest. This treats a colony nobody can see or reach, which is precisely why it works where a spray does not.
- Leave the route open. The entrance stays open until the colony is dead. Sealing it early is what drives wasps indoors.
- Proof afterwards. Once activity has stopped, closing the gap, replacing a broken air brick or fitting a vent cover stops a queen choosing the same cavity next spring.
The nest itself is normally left in place. It is inert once the colony is dead, and opening a wall to retrieve it causes more damage than it prevents. See wasp nest removal for what a visit involves.
How long the wasps keep coming
Activity falls away over the days following treatment rather than stopping instantly, because foragers that were out at the time return and pick up the product. Seeing wasps at the entrance afterwards is expected. If traffic has not clearly reduced within a few days, that warrants a call back.
Related reading: wasp nests in the roof or loft, when wasps are most active and are wasps dangerous.