I am concerned that installing my toilet directly on the concrete floor may eventually cause the toilet to crack. Does anyone have experience with this? Maybe toilets do just fine in contact with concrete.
I was thinking about placing thin rubber matting where the toilet makes contact with the concrete, but hopefully this is not really necessary.
A toilet was installed in my basement during construction for the workers to use instead of a porto potty. It's sitting on the concrete with a couple little spacers under where the screws are in the floor (like 1/4" gappers used for tile). It's been like that for 10 years and seems just fine.
As above it's about the same as putting it on concrete. If you put it on foam or rubber you might actually make it rock MORE then without those things. If your really concerned put it on a thin piece of plywood.