Why It’s Better to Avoid Paving Asphalt Over Concrete

It is a question we hear from homeowners with an old, cracked concrete driveway: “Can’t you just pave asphalt right over it?” On paper it sounds like a money-saver. The old surface is already there, it is hard and it seems like it would make a decent base. In practice, laying asphalt on top of concrete creates a set of problems that tend to show up quickly and are expensive to undo.

One note before we start. Dan The Paver installs asphalt only. We do not pour, repair or replace concrete. When we talk about concrete here, it is because that is what many older driveways are made of, and understanding how it behaves under asphalt helps you make a better decision about your new driveway.

Reflective cracking

This is the biggest problem. A concrete driveway is built in sections separated by joints, and older ones usually have cracks as well. Those joints and cracks move. As temperatures change, each section expands and contracts on its own. In winter, moisture under the sections can freeze and shift them slightly.

When asphalt is laid on top, it bonds to a surface that keeps moving in a pattern. Before long, the joints and cracks below “reflect” up through the new asphalt as matching lines. You end up with a driveway that looks like the old one, except now the cracks are in your fresh asphalt.

A poor bond between layers

Asphalt bonds best to a properly prepared aggregate base or to existing asphalt. Concrete is dense and smooth by comparison. Even with preparation, the bond between the two materials is weaker than it would be on a proper base. Over time, especially with water getting between the layers, the asphalt can start to slip, shove or delaminate under turning tires.

Water gets trapped

Water inevitably finds its way through cracks in the new asphalt. On a normal base, it can drain downward. On top of concrete, it gets trapped between the layers. In a New Jersey winter, that trapped water freezes and expands, pushing the asphalt up and breaking it apart from underneath. In summer, it simply sits there and weakens the bond further.

Height and drainage problems

A new layer of asphalt adds height. On top of an existing concrete surface, the finished driveway ends up higher than it was designed to be. That can create:

• A step up at the garage, sometimes enough that water flows toward the garage door instead of away from it.
• An awkward lip where the driveway meets a walkway or the street.
• Changes in how water drains across the property and into your lawn or your neighbor’s yard.

Fixing those transitions after the fact is difficult.

Hidden base problems stay hidden

If the original concrete cracked, heaved or sank, there was probably a reason: poor soil, bad drainage, tree roots or an inadequate base. Paving over it covers the symptom and leaves the cause in place. The new asphalt will eventually follow the same movement.

So what is the better approach?

In most cases, the right way to get a durable asphalt driveway where a concrete one used to be is to have the old concrete surface removed, correct the grade and soil, build a proper compacted aggregate base and then pave a full asphalt driveway. Our companion post on why you should remove a concrete driveway before paving asphalt explains what that removal opens up for you. During your estimate we can talk through how removal of the old surface will be handled as part of the project.

If you are still deciding between materials, our comparison of asphalt vs. concrete driveways in NJ lays out the trade-offs.

The bottom line

Paving over concrete may save money on day one, but it rarely saves money over the life of the driveway. Starting from a proper base gives your asphalt the foundation it needs to handle Jersey winters and summers.

To plan a driveway built the right way, see our asphalt driveway paving service and schedule a free estimate.