Hi there,
Does anyone know what the stuff is you sometimes see walls made of, in rooms I would guess were built or altered in the 1950's? There's a 1/2 - 3/4" thick outer layer, adhered to a second layer of similar thickness, with evenly spaced, round perforations. A cement looking product seems to have dripped through the perforations in the second layer, to hold the first one to it. It's hard to know what the size of the components of the outer product would have been. But from the back, the second (perforated) layer, looks to have been attached to the studs, in strips of 18 - 20" in height, running horizontally. I'd be grateful for any data anyone could share. Thank you.
Best,
Will