I'm renovating a 120 year old house, and have a few questions I need help with. We're replacing the plaster/lath on the walls. One ceiling has wallpaper that we want to keep. Being old, and over brittle plaster, I don't want to try to peel it back any, I can't get replacement. So, how do I tape/mud the wall,ceiling juncture without harming the paper on the ceiling? When I built the new bathroom I put backer board around the tub walls and then used plastic shower walls. The backer board extends a couple of inches past the tub/shower surround and I plan to run a vertical row of ceramic tile for a border. The backer board butts up to the sheet rock. I use paper tape on the sheet rock seams, and fiberglass mesh on the backer board seams. Question is; what should I do on the seam where the backer meets the sheet rock? I don't think tape works for backer, but the mesh is a bit thick to use over sheet rock. So, which way do I go? Thanks guys!