Holy moly!
I reckon 3 tonne bags would do it, you'll have enough left to create a beach resort!
Going to need a few tons for between the slab and hardcore. Thats why ill be getting 10ton in. Im sure itll take another 5 or more plastering sand for the rendering! If the slab is 11x8x 50mm that works out at 4.4 ton!
