Hello Folks, I live in a condo unit with two stores and a basement, mostly made out of concrete and brick walls. There are two walls separating the condo units in the same building (4 units in each building). There is an opening in between the walls on the spot whereon the ductwork meets the chimney inside the wall (there is a gap between the walls where the chimney is located); in effect is a opening between my unit and the other unit that I would like to close and through that opening it wires and pipes also pass through. Below are some pics of the situation: I would like to close such opening. Any suggestion on how to approach such issue would be appreciated.