Closed cell spray foam under concrete? What???

I’m just showing something we have done a bunch of times that a lot of people have never seen. Get a good spray foam contractor to shoot closed cell spray foam under your concrete in a radiant heat application. It’s 1-1/2” thick seamless. The stone or gravel needs to be dry and it will stick really good. It works especially good if the slab has any kind of a haunch.