Over the past year I've noticed a few hardwood floorboards buckling up, and it's getting worse.
Some of the buckled spots feel hard and solid, like it's solid wood underneath, some feel hard yet hollow, and others are completely soft and spongy. The warped boards are scattered all over my house, though they do tend to occur in runs. You can see what I mean in the image I linked to below.
Here is some info about my house:
* House and floor are both about 55 years old
* House is located about an hour from the gulf coast, so it gets pretty humid around here
* House has a crawlspace
I can't figure out what's causing it. It seems to me that the only thing that could cause all the symptoms is water, but I've looked under the house, and I can't see anything obvious. And the house and floor are both so old that if it were a simple moisture problem from under the house then surely it would have shown up before now, right? Why all of a sudden? I can't find any signs of a roof leakage either.
Here's a very crude drawing of my house, to give you an idea of what I'm talking about. The red stuff is the buckling.
http://i.imgur.com/6kelk80.png (I can't get it to directly show the pic)
If it might be another clue, the first buckling I noticed when all this started was in the living room, on the left side of that run in the picture (close to the hallway). Everything else developed later.