no studs in my plaster walls?
I live in a 110-year-old row house. The shared walls on either side are plaster. The sound insulation provided by the shared plaster walls is terrible. I have read that plaster is supposed to be more sound-proof than drywall, but that's not my experience here. You can hear normal speaking voices through the walls. I can just about follow along with my neighbors' conversations on one side in particular, though they are not being particularly loud. The other side is a bit better, which may be due to different wall construction on the interior of that neighbor's house.
My master bedroom spans the width of the house and thus shares a plaster wall with the neighbors on both sides, and like I say, on one side in particular you can hear normal speaking voices. I want to leave the plaster in place and screw 1x3 furring strips where the studs are, and then screw two layers of drywall to the furring strips. I will also take additional soundproofing measures like Green Glue between the drywall layers and caulk around the edges, etc. I'll lose a couple inches on either side of the room, but I'm fine with that. For starters, though, I have to find the studs, and I am starting to think there are none. I have put 2 1/2 inch drywall screws all over the place in the wall trying to find them, starting with logical places like 16 inches from the corner. There are indeed some places where the screws grab pretty strongly, but there is certainly not as much resistance when I'm turning the screws as there would be with studs. In some places I find reddish dust in the walls all the way to the surface of the plaster. In some places my screws hit some kind of hard masonry product about an inch deep and won't go any further. In some places it's grey-white plaster all the way through.
I'm not finding any hollow spaces except behind an outlet. The outlet box is not attached to a stud -- it's just floating in the plaster. Through the holes in the outlet box I can see what looks to be the back of my neighbor's wall, and it is a light greyish color and is a flat, rough surface. It's not as bumpy as the back of a plaster wall would be -- it's more flat.
The good news is that the plaster wall appears to be very strong -- strong enough that I would almost consider gluing and screwing the furring strips wherever the screws seem to hold well. I can hang a 2-gallon can of primer from one of the screws and it doesn't budge, and I definitely cannot pull the screws out with my hands. That said, I'd certainly prefer to find studs.
Any guesses as to what's going on inside these walls? The thought crossed my mind that the red dust is rotten wood, but it doesn't appear that way to me. It's almost clay-like, but dry. It's very fine dust and very uniform.
Downstairs, I opened up one of the original interior walls and can see full 2x4 studs, 16 inches on center, along with the old lathe that was left inside the newer drywall. So I expected to find studs in the exterior (shared) walls as well. Wrong assumption?
Thanks for reading my long post : )