Am I right in thinking that plastering on walls that have been painted, especially with flaking paint is a no-no.

Just been stripping some wallpaper and finding that the skim coat is just coming off easier than the paper! Initially thought it was damp that was causing all the dull noises when tapping the walls. It turns out that the plaster had blown due to it not sticking to the wall in the first place! In some places there was wallpaper under the skim. Nice skim coat, shame about the lack of preparation.

What's the best method of fixing this, 1) removing the base coat and starting again, or 2) sand down to remove all paint and PVA the walls then re-skim, or 3) something else.

Can't move, but then we're not living there. It's a development property.

Thanks. Having had a closer look the other day and more plaster has blown than I initially thought by tapping the walls so dotting&dabbing sounds good, though lots of other places has blown in isolated spots so those I can re-do. Just surprised that the previous plaster skimmed over wallpaper and paint - probably did a quick bodge job and got paid for a proper job knowing that it would last for sometime before any problems appeared.

To the stage where you might as well redo the whole wall. Some bits of plaster are quite firm and didn't come off at the slightest touch by my wrecking bar, unlike many other patches. I'll have to put up a picture sometime when I next catalogue my batch of pictures.