Under the non-insulated floor, laid on the ground on a layer of well-compacted earth or sand, you need to make the substrate z 10-15 cm layer of lean concrete. Its surface should be carefully rubbed smooth with a steel float. Only on top of it you can lay a waterproofing made of at least two layers of good-quality roofing felt or construction foil. You have to remember here, that the insulation strips are placed crosswise in both layers. Then a leveling layer of concrete is laid in thickness 4-5 cm and an underlay for the floor.
