Ok, so, over the past year we just might have developed some kind of small tiny issue with one of the basement walls:
Yeah. That is indeed a picture of all the paint and plaster just falling off that wall in sheets because of an incredibly small amount of unstoppable moisture coming in from who knows where. Finding the source would probably mean having to take apart our entire house, since this is a center wall that is shared with a neighbor who is experiencing none of this on their side.
On the plus side, once all the plaster fell down, we realized that now that the wall was exposed to the air, whatever moisture was being trapped under plaster was simply able to evaporate without causing any more problems. But on the minus side, it looked like a wall where all the plaster had fallen down. Our solution? Cover the wall with something that wasn't airtight and wouldn't actually touch the wall.
First, I put up a few waterproof 1"x3"s (I think they are usually used as outdoor trim):
And over them went a layer of this bamboo wall covering,which comes in 4 by 8 foot sheets with a nylon mesh backing:
Here's a view looking down the stairs:
Problem solved, if I do say so myself!