Concrete Subgrade Preparation – Grading and Drainage Planning

Concrete subgrade preparation is vital to a long lasting driveway!

All driveways need a certain amount of excavation and grading before installing the concrete. How much, is the question?

2 things need to happen for a good, solid driveway:

1) We want to make sure the sub-grade is stable so the driveway is built on a solid foundation. A driveway is only as good as the sub-grade beneath it.

2) We want to make sure the concrete sub-grade preparation is done so the water drains and sheds water properly.

It’s vital that water runs away from the garage or home to avoid flooding so the driveway needs to be graded to ensure drainage away from the house or garage.

We also want to make sure water runs off of the concrete and doesn’t pool or stand on the surface of the concrete.

These two factors alone require most driveways have grading done before installing the concrete.

Believe it or not, some contractors will put very little time into grading the driveway properly and in the end you may end up with a problematic driveway that lasts half as long as it should, or even worse… a driveway that causes water to flood your home.

Long Driveways

If you have a long and winding driveway leading up to your home, should the driveway be graded and paved with a crown, or should it be graded flat?

Grading a driveway with a crown is not recommended for a long driveway. The problem with a crown is when you drive on the driveway with your vehicle, the tires run on both sides of the crown, straddling the hump in the middle. This will cause the concrete to push down and outward on both sides, pulling the concrete away from the middle and cause cracks that are parallel with the driveway.

Obviously, we want to minimize the cracking of our newly installed concrete driveway as much as possible so grading the driveway and installing the concrete flat, but pitch it to one side or the other so the water will drain off is the right way to grade a long driveway. It doesn’t have to be a drastic pitch, but only about a 1/4 inch to 1/2 of an inch on either side. This will result in less maintenance and a much longer lasting driveway.

Keep in mind, on very rare occasions should a driveway be installed with a crown in it.

Crowning a driveway is actually a common rip off practice by the “fly by night” unethical contractors.