My home was built in 1958; load bearing wall on garden level has dropped away from ceiling in the last two years. (It looks like there may have been a similar problem more than 20+ years ago.) The gap is now at 1/2 ". The slab on garden level has dropped as well, about 1/3". There is a cement slab outside the offending wall with an outside spigit. There are no signs of leaking, though prior to my purchase 20 years ago there had been. We are way down on yearly moisture in the last few years.
Help! Walls are starting to crack as well. Had engineers out to no avail.