Rise in basement floor - can't find cause
We have sufficient grade, as no water ever collects. There is one downspout on the side of the house that the bottom part sometimes gets knocked off. I'll check it out and find out about the rebar, too. I wonder if the thaw-freeze-thaw-freeze pattern is aggravating things.
Our soil is more on the sandy side, so clay content is probably not the problem.
The actual cause is probably that we decided to sell the house. An amazing number of things have broken down since we made that decision: The upstairs bathroom wall suddenly fell in, the garage door opener exploded, the furnace thermostat stopped working, etc., etc., etc.