Updated: I had added a picture of one of the wasps. They are very small, perhaps 10 - 15mm in length. One stung my wife on her finger.
I think these are a wasp of some kind? The appear all black or very dark. Cannot make out any orange or yellow markings. I can make out raked back wings. They are high up under the eave of our multi story house so I cannot get any closer to inspect, the picture is zoomed in from the ground. I haven't seen any flying at all or buzzing around, just walking around the nest. Looks like a mud type substance.
Location is Tuggeranong, ACT.