One day while at work I was talking to an engineer and he said for our neighborhood foundation piling need to go 18 feet deep to hit something solid. As he said the area was all at the bottom of a bay at one time, and that's were the gumbo soil/clay came from.
Where I grew up outside of Chicago everyone had a basement or crawl space. Our was a cider block build with no rebar or concrete inside the blocks. We had a crack around rte basement that was freeze line deep. It was eye opening how much the walls actually moved with the seasons. At least we didn't have radon gas in our basement.
Cider blocks..... yum!!