Just short of taking the Hilti to it, I'm trying to determine what is the wall construction of my wall is . I can hear the adjacent resident next door. I'm in a old bldg in Chelsea, NYC. The primary wall is 5/8 sheetrock on what appears to be plaster of some sorts underneath. The plaster seems to be around 3/4 to 7/8 thick. However, when I took a sheetrock saw to it, cutting a 4 inch square, there did not appear to be lathe holding it.

However, after cutting the full square, the plaster would not budge. It's as if it has a *concrete slug* if I'm coining the term right, behind it.

I am trying to locate studs behind this plaster wall and I suspect there is none ? Behind the plaster, there appears to be only 1.5 inch at most of free space.

My next plan to to knock out the 4" squre I cutout and confirm if there is cinder block behind this ?

I've asked our landlord and super and both are unsure what is holding this plaster wall up.