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How to Prepare the Surface for a Concrete Driveway

By Larry Simmons ; Updated September 21, 2017

Successfully pouring the slab for a concrete driveway requires that the surface beneath the driveway is properly prepared. This surface, or subgrade, must be uniform in firmness, grade and dampness. You’ll have to excavate your installation surface to a consistent depth with a graduated slope to protect the slab from gathered water. You’ll also need to place several inches of compacted material in the excavation to keep your driveway from sagging or sinking. If the subsurface is properly prepared, the actual pouring and finishing of the concrete should be trouble-free, and your concrete driveway should have a lifespan of decades.

Step 1

Mark the dimensions of your driveway on the ground, using landscaping flags to outline the excavation site for the concrete slab.

Step 2

Dig the area to a level depth of between 4 and 10 inches, depending on the strength of the soil and the weight of the vehicles that will be using the driveway. Looser soil or heavier vehicles will require a greater depth, for both a thicker layer of subgrade material and a thicker slab of concrete. Allow for a slope of 1/8 inch for every foot of driveway length leading away from any permanent structures.

Step 3

Use a vibratory plate compactor to firm up the surface of the excavation. Run the compactor across the entire surface, compressing the soil.

Step 4

Build the form used for the concrete pour. Line the edge with wood planks cut to the height of your slab. Sink the forms firmly into the ground.

Step 5

Add a layer of construction gravel. Place the gravel in the hole, 2 inches at a time, compacting each level with the plate compactor. Build the gravel up until you’ve reached the required level of material--a minimum for any driveway is 2 inches of gravel followed by a 2-inch concrete slab. Thicker gravel will provide a firmer footing for the slab, allowing for thicker slabs and heavier vehicle use. Maintain the slope away from permanent structures.

Step 6

Wet the gravel before pouring the concrete. The gravel should be damp, with no signs of pooling water, to prevent the stones from leeching moisture from the poured concrete.

 

Things You Will Need

  • Spade
  • Landscaping paint
  • Vibratory plate compactor
  • Concrete form
  • Construction gravel
  • Water hose

About the Author

 

Larry Simmons is a freelance writer and expert in the fusion of computer technology and business. He has a B.S. in economics, an M.S. in information systems, an M.S. in communications technology, as well as significant work towards an M.B.A. in finance. He's published several hundred articles with Demand Studios.