Grading for a New Driveway

Determining the Pitch

• All driveways should have a slight angle to direct water from the surface. If the site is flat, a 2 percent grade, or a decline of 1/4 inch with every 4 feet of length, is enough to manage the flow of water. If the driveway site is naturally sloped, the pitch can be as steep as 12 percent. Note that steep driveways can be slippery and dangerous in wet weather. If possible, lay the course of a steep driveway on a broad curve to reduce the incline.

Preparation

• Preparing a site for grading is a straightforward but laborious process. Once the site is measured out, lay down garden stakes and connect them with a string to outline the exact size and shape of the driveway. Check that it is at least 14 feet wide on curves and 10 feet wide at straight sections. All grass should be transplanted to another area of the yard and the topsoil removed so the site is at least 12 inches deep. Use an excavator machine to do the digging, especially if the driveway is long. A driveway foundation must be laid over hard ground. If laid over topsoil, the foundation gravel gets pulled down, causing the pavement to sink from lack of support.

Grading the Subsoil

• Once the site is excavated, it must be graded so the foundation and pavement will follow the same slope. A simple way to do this is to park a tractor at the end of the site closest to the house. Attach a grading blade to the back, and set it at 1/4 inch per foot. Set the blade down so it touches the surface of the dirt bed. By driving the tractor slowly down the site several times, the blade will smooth and disperse the dirt into the set angle.

Grading the Base

• Once the subsoil is graded and compacted, layers of 3/4-inch aggregate are added to build up a solid, water-permeable base. If you’re paving the driveway with concrete, asphalt, pavers or another material, run the grading blade over the aggregate base before you compact the top layer. Do the same for the top layer of a gravel driveway to ensure it has uniform thickness and a consistent slope. Plan to re-grade a gravel driveway every few years to smooth out the lumps and low areas that form with normal wear and tear.