Quote Originally Posted by ChunkyMonkey View Post
To keep it simple..anchor to the bottom but build it w/ its own roof 4 inches short of the basement ceiling (like a safe room), so you don't have worry about settlement.

I was planning on leaving a few inches to spare at the top anyway, but I'm a little concerned because the slab has cuts in it (to guide cracks) and one of them is right in the middle of the room I was planning.

ChunkyMonkey, you're thinking in the right direction. I considered steel, but in my limited research, it seemed that concrete was easier to work with and had a better strength to cost relationship. I could be convinced otherwise... I haven't done enough research yet.