Build A Gravel Driveway
DEAR TIM: I need to build a gravel driveway on some land I recently purchased. Is a gravel driveway going to hold up as a permanent driveway paving solution? What types of gravel are used for a driveway? Do you think I can construct a build-it-yourself gravel driveway? Ed M., Basking Ridge, NJ
DEAR ED: Congratulations on your new land purchase! Over a year ago, my wife and I did the same thing with the intention of building our retirement home. Currently, there is a rough gravel roadway that extends to the top of our property. Just last week, I was at my land to start the process of extending this gravel driveway up to our new home site.
The simple answer is a properly designed and constructed gravel driveway can function as a permanent driveway paving solution, and with some rented equipment you probably can do the job. There are hundreds of thousands, if not millions, of gravel roadways and driveways in the USA. They work well, but come with a small amount of periodic maintenance issues. But the lower initial cost of the gravel driveway is often reason enough for most to deal with whatever needs to be done to keep the driveway in good shape over the years.
The first thing I would do, if I were you, is to research basic road-building techniques. College textbooks that deal with introductory civil engineering often cover this topic very well. A long-lasting gravel driveway needs to have all of the same design characteristics one finds in a well-constructed major roadway. You can often find great information on the Internet if you can't locate a road-building textbook.
For starters, the soil under the gravel driveway must be well-drained and strong. It also must be free of any organic material like sticks, tree roots and leaves or grass. All topsoil must be stripped off the driveway location and stockpiled for use at some other place on your lot. It is a very bad practice to build a driveway on top of spongy topsoil filled with organic debris.
Water is the enemy of gravel driveways and any roadway. Surface water can erode the gravel off the surface of the driveway and subsurface water can turn strong subsoil into a quagmire. The weight of cars and trucks pressing down on a gravel driveway is not much different than the powerful hydraulic pressure used on construction machinery, car lifts and any other machine that uses the leveraged force of hydraulics.
Water that is forced under pressure under the gravel can transport silt from the subsoil into the gravel. As the silt squeezes between individual pieces of gravel, it causes the friction bonds between individual pieces of gravel to weaken. When this happens, your gravel driveway can fall apart in no time.
It is often a great idea to install a geotextile fabric on top of the subsoil before the first layer of gravel is installed. This fabric prevents the silt in the subsoil from fouling the gravel. These products come in wide rolls and can easily be installed by two people who just unroll the fabric allowing it to lay on the soil. On windy days it needs to be covered quickly with a 4 or 6-inch-thick layer of crushed gravel. If you don't do this, the fabric might end up on your neighbor's lot.
The first layer of crushed gravel needs to be a larger-sized gravel. Try to locate stones that are the size of baseballs or even softballs. NEVER use pea gravel nor rounded river rock gravel. These stones are like ball bearings and will easily roll and move as tires start to spin. A car or truck can would never stand a chance going up a hill with rounded gravel as the wheels would spin like a top. Angular gravel interlocks with adjacent pieces and the combined mass can act as one larger piece of rock.
Add additional layers of crushed rock in 4-inch thick layers with each layer being a smaller sized stone. Compact each layer with a mechanical roller or tamping machine. The final layer of gravel should have pieces of angular stone no larger than a golf ball, with many of the stones being the size of marbles. If you can install 10 - 12 inches of gravel on top of the geotextile fabric, you should have a gravel driveway that will last decades.
Be sure the gravel driveway has a crown in it. This means the center of the driveway is always higher than the two edges. The crown allows water to flow off to the sides of the driveway preventing any ponding of water on the gravel surface.
Gravel driveways need some periodic care in the form of grading or dressing. Low spots need to be filled with gravel scraped from any high spots. If your driveway has curves, you will discover that car and truck traffic tends to push loose gravel to the outer edges of the curves. This gravel needs to be brought back to the center and inner part of the curves.
Gravel driveways built on hillsides need ditches on the high side of the driveway. These ditches capture surface water that runs down the hill and otherwise would run across the driveway. Larger angular rocks should be placed in the ditch to slow down the speed of the running water in the ditch. Monitor the ditch to ensure the running water is not cutting too deep a channel or eroding the ditch causing failure of the gravel driveway.
Leo Kudej of Haymarket, Virginia, offers these comments from his years of experience.
I think you need to tell the readers just what they need to apply to the road bed layers. This way they can just call in to their local quarry exactly the type of stone they want.
The build up should go as follows - the first layer will be #3 stone (fist size); the second will be #57(little less than ping pong ball); and the final will be #21-A, or called crusher run (thumb nail sized stone with stone dust mixed in with it).
With a layered set up like this, you will have a driveway that will last many, many years. I am a carpenter, but living up on Bull Run Mountain for 20 years taught me a little about gravel roads." Leo K.