I live in an East Coast row-house built in the early 1920s. There is a 3" crack in the solid brick party wall that I need to address (see photos). My neighbor's baby's room is on the other side and her crying comes right through.
Before readers freak out, some background:
My house was built later the neighbors house, and my house sticks out further in the back. Above the first floor, the bricks of the two houses are not interlocked--that is, there are two brick walls side to side with nothing connecting them. The back yards also slope down steeply. So it is no big surprise that this huge crack formed. I had the house underpinned when I moved in about 15 years ago so the movement has mostly stopped. But the crack expands and contracts slightly through the year, probably due to temperature changes. I monitor it in the attic and it moves about 3 mm a year--it's smallest in the spring, and largest in the fall.
I have now uncovered the crack (there was wire mesh and plaster over it the last 15 years) and need to decide how to fill it. I am thinking cut bricks and concrete. Because the crack is at its largest width right now, hopefully having solid material in there will help stop the movement.
But I'm also a little worried that when the brick walls want to come together 3 mm in the spring and there is a huge amount of pressure between the two wall sections (in the previously open gap), cracks will appear somewhere else, or the walls will twist or something.
If my question makes any sense at all, I'd welcome advice on the best way to fill the crack (or whether it is better to fill it with something flexible?).
Also: Is hydraulic cement better than concrete to put between the bricks?