apartment therapy changing the world, one room at a time

You need to scrape and clear away ALL lost plaster -- a messy job -- and then re plaster, otherwise the problem will come back very soon.

If this is a rental, then get your landlord to deal with it. If you own it, it is really worthwhile getting professional help.

meant loose plaster (not lost!)

1.Grind down the painting
2.Paper the wall with glassfabrics
3.paint the wall again with white color.

It depends on how long you want the paint to last and if you want a smooth finish. For smooth, you'll have to do lots of scraping. If you actually only want non-peeling paint, then you can scrape the existing paint down, do a sanding (an orbital sander will make your life easier) and then repaint.

Our walls were terrible, and the contractor used a type of mesh that was plastered over. Took a long time, but might be worth investigating, since I think any solution is going to take a long time.

You need to hire a dry-wall contractor if this is your house and not a rental. From the small picture it looks like what you've got going on is a poorly done repair job but it's hard to tell from just that one small picture. It's not clear if this is standard drywall or a plastered wall. It looks like somebody just put a bunch of drywall mud (joint compound) over some wall damage. Joint compound is water soluble so it may not have been sealed properly (?). The mesh someone mentioned is a good idea but only really for cracks, not large areas. You can't rely on plaster or drywall joint compound for structural strength - that's what someone did before you and as you see, it doesn't last.

But you really need an expert to look at that. There's more going on there than meets the eye. You're obviously dealing with a shoddily done repair that's coming undone.

Just add a lot more sand texture and you won't notice the uneven patching and cracking. Embrace it. Go for a day-at-the-beach palette!

is this a focused failure of the shown surface or is the structural composition of the room failing? do you rent or own?

as belbal indicated above in the comment, glassing fabric would solve the issue on any scale.
the implementation of glassing fabric is different on scales.
you could glass the whole room by fabricking every surface then expanding a balloon to hold the glassing fabrick to the surfaces which would give you a big structural shell after composite cure -or- you spot treat the issue successfully with glassing fabric as explained by belbal.

the complexity of the issue can be solved by rotating the posted image 180 degrees.
is it a boat hull or a bathroom ceiling and what detail of surface finish is your intent.
if your desire is a smooth glossy finish to the surface with limited shadow play the underlying structures original design intent is the possible failing issue.

Boomer, actually the mesh used was for the entire wall. It was different from the mesh used for patching cracks.