Think twice before trying to remove wallpaper from your plaster walls. You might cause more damage than is already there. And most of it will probably not be your fault.
Plaster + Wallpaper: What Is It Hiding?
Old plaster and lath walls often have several layers of wallpaper that have accrued over the years.
One reason for is that the previous homeowners wanted to beautify the house. But there may be a more insidious reason: they wanted to hold together crumbling plaster walls.
Not all homeowners care enough to properly maintain and repair their plaster walls. Some just want the thing done, no matter how sloppy the work.
Thus, you may find that your home's previous owner applied wallpaper to crumbling, cracking plaster walls chiefly as a method of holding the plaster together.
What To Do
Unfortunately, it actually does work, to some degree.
Several layers of wallpaper will bind cracking plaster. But eventually whatever is happening to the plaster will transfer to the wallpaper. So, plaster cracks will mirror themselves on the wallpaper. It's a short-term solution, and a lousy one at that.
Before attempting to remove wallpaper from your old plaster and lath walls, be ready for the worst and do not expect to be able to preserve the plaster.
If you manage to get the wallpaper off and the plaster hangs together, consider yourself lucky.
In most cases of multiple wallpaper build-up, though, the plaster will be a lost cause. Pull out all remaining plaster and lath and re-build the walls with drywall or, to be historically accurate, plaster and lath.