Ron wrote in news: snipped-for-privacy@33g2000yqm.googlegroups.com:
We had that too. In fact, twice. Caused by an imperfect bathtub install that left a crak between the tub top and the tile. It was all fixed. However, I will not easily forget the experience of hearing tiny sounds like grit falling, seeing the ceiling slowly come loose and just before getting the drop cloth down to get the ceiling, seeing a piece of plaster of about ~3x5 ft come down in the living room while still standing in the kitchen. That's when I learned that after a new bathroom installation you should keep the tub filled with water for a few days before tiling the walls around the tub, so as to make the floor settle properly (or something like that. The tile guy was going on vacation, hence the rush by the contractor).