I'm renovating a 1905 farmhouse and have to pull the exterior wall out of the main floor bathroom in order to fur out the 2x4 walls and properly insulate. The bathroom was renovated sometime in the past, and the walls are plaster over metal mesh. I'd actually like to leave the plaster because it's in good shape and forms an interesting arched ceiling - probably pretty 'classy' in its day. I don't however, want to re-install plaster on the exterior wall. The bathroom is long and skinny - 4' x 11', and the exterior wall is one of the short 4' walls. Is there a way to transition between drywall and plaster? I've heard that drywall mud won't stick to plaster. Any ideas?