Hi guys. I want to build up a 3000 mm by 1800 mm garden shed on some left over patio slabs. I searched the net and they advised on digging up a 75 mm deep hole as large as the area of the shed, fill the hole up to at least 40 mm with ballast and cement dry mix, then concrete and slabs on the top. My question is: what is the point to add cement to ballast if i do not wet it? Isn't it better and probably cheaper to just put ballast or hardcore, then concrete on the top and press slabs down? As for the concrete base to press slabs down, do you make the concrete by mixing 1:6 cement and building sand or sharp sand..............i mean which one is better and why? Thanks for your help.