Yes, brick buildings are common places for yellowjackets to nest. They often access the wall interior through weep holes and cracked mortar joints and then build their nest inside.
Chicago has a lot of brick houses, especially in older neighborhoods. They’re stylish old homes and solidly built too. But the trouble is that brick veneers are not solid and yellowjackets are able to get inside and then build nests.
Brick veneer is not solid. There is an air gap between the brick and sheathing behind it, and weep holes in the bottom course let moisture drain out of that space. Those holes are purpose-built openings and they’re about the width of a mortar joint. Yellowjackets can easily fly inside. Cracked or missing mortar can lead to similar issues.
Once inside, a yellowjacket has what they want: a dark, dry space that’s large enough to expand into. And that’s exactly what they do. By August, a wall void colony of wasps can hold thousands of workers.
Here’s how you can know this is happening to you. If you see wasps entering and leaving the same small opening in the brick every few seconds on a warm afternoon, that’s clear evidence. Buzzing or rustling in the walls is another. Sometimes wasps will even appear in upstairs rooms.
Don’t caulk or seal openings while colonies are inside. Trapping thousands of yellowjackets only serves to make them desperate. So they chew a way out and push toward light. That might put them in your home. And also, never spray a weep hole from a ladder. That can cause them to swarm and you to fall off the ladder.
If wasps are in your wall, you need a professional to treat them, full stop. Once the colony is gone, you can install weep hole covers or stainless mesh inserts to block insects and rodents. Then you can seal up any cracked mortar joints too.
If wasps are getting into your walls, Mosquito Squad of Chicago can help. Mosquito Squad locates and treats stinging insect nests, including wall void colonies, and treats the openings they use. This will help you protect your home before the next season's queens arrive.
