In our victorian terrace the plaster in many places is very old and uneven. Under one windowsill the plaster has quite a large crack which is also a patch where the plaster is loose. If I tap the wall there it sounds hollow for about a foot diameter.
What is the best simple fix for this? My guess is I should avoid knocking the plaster off the wall as patching that would be a professional job. Would filling it and sanding it hold? Should I paper over it?
Or does the hollow plaster simply have to come off?