The way it works is the mattresses are put on the concrete. Then we cover them with foam - it looks like what you put under carpet. Then a giant top cover goes over that. Then we put sawdust on it continually to help keep it clean.
We were visiting today and Kris was testing them out. We all joined him.
They were really comfortable. Of course, I fell asleep on cement yesterday, so I'm no princess and the pea.