Hi Folks If I use a  suspended concrete ground floor, how best should the ground below be finished? I know that the the ground needs cleared of topsoil, 150mm void, and periscope ventilators will be required. However, should I put down a layer of blinding, or hardcore topped with  blinding, or can I get away with leaving the earth exposed? The area I'm in does not require any radon gas layer, and the stony clay is about 1 to 1.3m deep before bedrock is hit. Thanks, Chris