I guess your wondering Why so high out of the ground?? It was a condition of the permit that the finished floor height be 150mm above the highest known flood level. This brings the raft slab to almost 1 metre high. Why a raft slab?? As the home will have polished concrete throughout to create thermal mass, the engineers believe that a raft slab will provide the best possible outcome for polished concrete floor with minimal imperfections.