Can You Pave Over a Gravel Driveway

Gravel driveways are everywhere in Southwest Virginia. They're on farms in Floyd County, on ridge lots outside Christiansburg and on long lanes that run back from the road across Giles and Pulaski. Sooner or later, a lot of those owners get tired of potholes, washouts, dust and stones in the yard, and they start asking the same question. Can you pave over a gravel driveway?

The short answer is yes, very often you can. The longer answer is that the gravel you have now isn't automatically ready to sit under asphalt. Whether it works depends on what's underneath, how water moves across your property and how the driveway is used. Here's how to think it through before you call for an estimate.

Why gravel can make a good starting point

Asphalt doesn't carry weight on its own. It's a wearing surface that sits on top of a compacted stone base, and that base does most of the work of spreading the load from your car, a delivery truck or a tractor. A gravel driveway that has been driven on for years already has stone in place, and some of it may be well compacted.

That's why paving over gravel is often less work than starting from bare dirt. The existing stone can sometimes be regraded, topped up and compacted into a proper base instead of being hauled away. When that's possible, it saves material and time.

When the existing gravel isn't good enough

Plenty of gravel driveways aren't ready to be paved as they are. Common problems include:

• Thin or uneven stone. Over the years, gravel gets pushed to the sides, pressed into soft soil or washed away. Some spots may have plenty of stone and others almost none.
• Soft or wet ground underneath. If the soil below stays soft after rain, it can't support pavement. Asphalt laid over a weak base will crack and sink in the same places your gravel ruts today.
• Mud and organic material mixed in. Topsoil, clay and leaves worked into the gravel stop it from compacting properly.
• Ruts and potholes that keep coming back. If the same spots fail every year, there's usually a drainage or soil problem that has to be fixed first.

In these cases, the base has to be rebuilt. That can mean digging out the weak areas, adding new crushed stone in layers, and compacting each layer before any asphalt goes down. It's more work up front, but skipping it is the most common reason a new asphalt driveway fails early.

Drainage matters more than anything else

Water is the biggest enemy of any driveway. On a gravel drive, water soaks through and runs off fairly freely. Asphalt is different. It sheds water, so the water has to go somewhere, and if it ends up running along the edges or soaking into the base, it will break the pavement up from below.

This is a big deal on the hillsides and hollows of our region. Before paving, a good contractor looks at:

• The slope of the driveway and where runoff from the road, roof and yard ends up.
• Whether the driveway needs a crown or a cross slope so water runs off to one side.
• Whether ditches, culverts or a pipe under the driveway are needed to carry water away.
• The low spots where water pools today, because those will be the first places to fail.

The EPA's gravel roads maintenance and design manual and the FHWA's gravel roads construction and maintenance guide both explain how shape and drainage protect a road surface. The same principles apply to a long private driveway.