If you have freezing and thawing and clay soil, you will save yourself a lot of yearly maintenance money by putting down geotextile or grade separation paper first. In Western Pa people always want to know what happened to their load of stone they put down last spring. When it partially thaws and it is driven over it drives the stone down through the clay and the water/mud comes up through it to the surface. If you have extra geotextile when done it can be used as a weed barrier around trees or in your garden.
