[bigstrat2003]

In fact, that approach is explicitly warned against for walls. When they can't get out their former entrance, they will start to chew through the wall to make a new one - and there's no guarantee that new entrance will lead to the outside, rather than your living room.

[foobarian]

My problem was the nest was hard to reach, and I was afraid that even if spraying did manage to kill the wasps, I would be left with a gross wet decomposing mass in the wall causing rot and water damage. I still need to figure out how to remove the existing nest but I'll wait until it's vacant :-)