The builders have got to casting the floor of my extension (they want to get it in before the Christmas break)
My plans show a floor made up with 125mm insulation underneath a total slab thickness of about 175mm of concrete. The insulation sits on blinded hardcore with dpm.
The builders are suggesting that about 100mm of concrete should go below the insulation, with the remaining 75mm on top, because the UFH would have less to heat below it (i.e. a smaller thermal store, I suppose)
I'm guessing there's not much difference in the overall effect, but thought I would ask if one way was any better than the other.
Does anyone have an opinion?
BTW, it'll be an electric mat style heater with ceramic tiles.