My friend's condo was built in 1960 and renovated before she bought it, in 2010 or so. Not long after she moved in, a chunk of plaster on the kitchen ceiling fell off, then a little later the same thing happened to a bit of wall. In both cases, the amount of material that fell off was only ~1-2 mm thick. But it was a fairly large area -- a couple of square feet in both cases.
Other interesting factoid: the damaged wall is about 2" thick: it is not a conventional drywall-on-studs construction. Feels and sounds like concrete, but it's not cinder blocks since it's only 2" thick. The ceiling also looks and feels like concrete, but I'm not positive.
Any idea what went wrong here? And, more importantly, how do we fix it?