Sub base is the term used to describe the layer immediately beneath the surface of a paved area. Typically the final surface will be made of stone paving, gravel, concrete or bitumen macadam. The sub base layer is beneath this and provides strength and stability to the surface it supports. Laying the final layer of paving on a poorly prepared surface will result in early failure of the pavement surface. Our sub base, or scalpings, consists of a graded blend of particle sized to a maximum of 40mm.