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New Gravel Driveway - How Deep to Dig?


We are preparing to have contractors put in a new 750' gravel driveway on our land. Each contractor seems to have a different opinion on how much topsoil needs to be removed before they can start laying down the base layer. One guys says all of the top soil and another are saying 6" is enough, and one guy suggested 2" We have no idea what the correct answer is.

The land itself is pretty flat and has approx 12" of good topsoil resting on top of hard clay.

Any guidence here is really appreciated as we want to get the job done right, but do not have thousands of extra $$ laying around either.

Traffic on the road would be pickups and occaisionally compact tractors.


Re: New Gravel Driveway - How Deep to Dig?

I don't know what the right answer is although I'd bet my bottom dollar that 2" is incorrect. I think a lot depends upon your soil. Have you talked to your local building inspector? He or she might be able to offer your some good advice.

Re: New Gravel Driveway - How Deep to Dig?

The right way to do it would be to remove all of the loam (topsoil) down to the sub-soil (hard clay in your instance). If you don't, be prepared to have the driveway regraded every year. During rainy weather, traffic on the driveway will cause the gravel to be pushed down into the remaining topsoil, leaving ruts, holes, & puddles. As time goes on, the problem won't subside...it will just continue every year. Installation of an underlayment fabric might help, but this is really no substitute for a properly prepared sub-base.

The guy who suggested 2" is an idiot.

Re: New Gravel Driveway - How Deep to Dig?

2" is not right. 6" is a little closer. Like the previous poster said, your soil will determine how deep to dig. There really is no preset depth. He could dig 6" and still be in mucky dirt. Whoever you hire needs to get down to solid soil and any dozier man worth his weight knows that. Don't get too crazy with the depth, because it could cost you twice as much in gravel. Just be sure it's understood the base needs to be on solid dirt. Be sure the first layer of rock is 3/4 inch or greater - depending on the soil. If you just start off with 1/2 inch most of your gravel will just be absorbed into the dirt. In my opinion that's the main cause of a bad driveway - people not starting with the right size gravel base.

Good Luck.

Re: New Gravel Driveway - How Deep to Dig?

I have to agree with Dave 357.If any loom is left the stone will sink into it. Once dug out use 2" stone for the base.

Re: New Gravel Driveway - How Deep to Dig?

I live in north florida and we have the famous georgia clay here (we are 5 miles from the ga. line) even though we have a gravel road we still have to have more gravel brought in from time to time because when it rains the gravel allows the water to go down and sit on the clay, the clay in turn gets soft and the gravel is pushed down into the clay resulting into have a clay road again. so proper grading before the gravel is put down is very important so that the water is allowed to run out and isn't trapped like water sitting in a trough.

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