Lime or gypsum?
Taking down blown plaster on a solid external stone wall (first floor) and found what looks like an old window, next to the existing window. I’m not sure how to redo this as there’s a real mixture of things going on in this 1850s cottage.
On the external side it’s rendered and painted white. Internally it’s lime underneath with a couple of layers of gypsum on top around the window, with a rock solid sand and cement finish within the window and gypsum on top.
I’m tempted to lime the exposed stone and gypsum skim the whole lot. Know that defeats the objective of using lime, but the rest of the wall is a mix anyway. Plasterer has suggested just battening and boarding over the top which I know may cause moisture problems but doesn’t seem like I can go all the way back to lime anyway due to the cemented window.
What would you do?