Is there any kind of plaster that can be applied over old drywall?

There comes a point in some home improvement situations when replacement makes more sense than salvaging. You may have arrived at that point with your walls. While new drywall is messy and troublesome to install, this operation will probably be less trouble than repairing old walls that may not have much life left in them anyway. Interior walls built in the 1950s were often made using first-generation drywall that came into use after WWII. It’s not unusual for this material to be easily damaged, especially now that it’s more than half a century old. Before giving up on removing the old wallpaper safely, however, try a wallpaper steamer if you haven’t yet. Any kind of wall damage can be repaired with patching compounds or plaster, though this is messy and troublesome if extensive areas need to be repaired. It may be that adding new drywall over your existing walls is the easiest option. You can simply apply it directly over the old stuff, with screws long enough to penetrate at least 3/4” into the underlying wood frame.