I am renovating a house . There is an extension which has a 3m by 4m floor approx 200 mm lower than the rest of the house. It is a concrete slab topped with 25 mm of polystyrene and chipboard.
I am thinking about how to raise it 200 mm reasonably efficiently...Possible options  celotex then screed  two layers of celotex then chipboard and  100mm kingspan then aircrete blocks laid flat with sand /cement brushed into joins..sort of like block and beam...what do people think?
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