Wasps are flying into a gap under a fascia board on my outside kitchen wall, no way they can get in , so presume they are nesting in cavity walls. Any suggestions?
You can buy cheaply one of those ustrasonic devices that plug into your mains. They do work in expelling unwanted intruders from your cavity wall. It works on their nervous system and sends a high frequency pulse which they cannot stand. We wondered why we had an excess of spiders trying to escape and realised they work on these also. Don't believe some people who say they don't work, I can assure you the latest type do.