The “Predalles” system is conceived to achieve a lightweight suspended slab; the underside and inner parts are plant-assembled whilst the outer casing is completed on site.

The bottom crust is made of a thin pre-cast concrete plank, which includes reinforcing steel rods and truss. Low-density polystyrene blocks are bound to the bottom crust, at modular spacing to form the ribs and the hollow cavities within the slab.


PredallesOnce the pre-cast crust has attained a suitable strength it is hoisted in its position on the structural frame, then the additional steel rods are placed to fulfill the design requirements and finally the in situconcrete is poured to pervade the gaps between adjacent polystyrene blocks and to create the topping and the connections with the rest of the structure.


This system was extensively used by Blokrete Limited at the Mater Dei Hospital Project. Concrete “Predalles” slabs 60-mm thick were used with polystyrene having a thickness, which varied from 180-mm to 380-mm depending on the span. Concrete “Predalles” slabs 40-mm thick with no polystyrene were also used on site for the roofing of small span service tunnels.