Dense aggregate Lightweight On shelves Bulk Cast Blue Engineering Fletton London stock Sand lime Cast 18 mm 0 11 1113 kN m3 Plastered medium density block Corrugated Sheet Sheet Expanded sheet Beam and block 50 mm topping Hollowcore plank Hollowcore plank Hollowcore plank Solid plank plus 50 mm topping 102 2 x 13 mm 100 2 x 13 mm