slab over room?

joel_4

Got a new one I haven't done before. I looked at a garage with a precast concrete floor. It has a full basement under the garrage that they also want to heat. We will be putting tube in the basement floor. So the question is what to do with the garrge floor. We will be tubing it as well attatching to wire mesh. They will be floating 3" of concrete on top I'd like to have thermal break, foil bubble??. But I'm concerned about how that thin slab would stand up if it wasn't directly adheared to the precast garrage floor. Anybody else come across this? any ideas?