radiant heat concrete floor on second level

Have put radiant heat in concrete on the first floor (bottom/ground floor in the States?) and want to put same on second floor. Am I going to have a problem with stability? What can I add to the concrete to make it lighter? How thick does it need to be? I'm putting an apartment in a barn so the basic structure is very solid. Pehaps a 'floating' floor over the present floor/ceiling would help. Any ideas would be greatly appreciated. The locals think I'm nuts (I'm also female, which doesn't help). Thanks.

Not sure, however I have a 50 year old radiant heat system in my house. On the bottom level it's embedded in the concrete floor, on the second and third floors it's in the ceiling.

Ceiling is fine, remember what it does it *radiates* the heat into objects in the room. So no problem up above. Just put insulation in your attic and you should be fine.

Oh and make a *map* of where all the pipes are. I have the original blueprints and they help a *lot*.

C