Construction Creates Our World

Why Does Your Driveway’s Foundation Matter So Much?

If you're installing a new driveway, then you may notice that your contractors spend a significant amount of time planning, excavating, and installing the foundation. While this may seem like a lot of effort for a part of your driveway you'll never see, the foundation is among the most critical aspects of the pavement. A poor foundation can lead to severe, and sometimes expensive, issues in the future.

Subbase vs. Subgrade – What's the Difference?

When you're discussing your new asphalt driveway's foundation with your contractor, you may hear the terms "subgrade" and "subbase." These terminologies can sometimes be confusing for the uninitiated. The subgrade is the lowest layer of your driveway, and it consists of the existing soil. Your driveway contractors will excavate the subgrade as needed to provide a level surface for the asphalt.

The subbase sits above the subgrade, and you can think of this as the first installed layer of your driveway. The subbase usually consists of various aggregate materials, ranging from chunks of concrete down to small pebbles and stone. Contractors can bind the subbase material with cement for heavy-use surfaces, but residential driveways rarely require this extra reinforcement.

These two layers taken together make up your new driveway's foundation.

Understanding the Importance of Your Foundation Layers

The foundation layers of your driveway serve two critical purposes: providing drainage and acting as the proper loadbearing portion of the structure. If your subgrade doesn't have the appropriate slope, water won't drain away from your driveway properly. Water that collects on or around a driveway can lead to a wide range of issues that may shorten its life and create numerous maintenance problems.

Together, the subgrade and subbase must also support the weight of the pavement and vehicles that travel on it. Your paving contractors ensure the integrity of these layers using a process known as proof rolling. In many cases, this technique involves driving a heavy vehicle (such as a fully laden dump truck) over the subgrade to test and compact it.

The proof roll exposes any weak areas and allows your contractors to repair them. Contractors usually need to excavate weak spots and replace them with more substantial material, such as an aggregate base. This process may require digging out several feet of soil in the subgrade.

Installing the Final Layer

Your contractors will install asphalt for your new driveway only after ensuring that the foundation is correctly graded, compacted, and tested. Taking these extra steps prevents your driveway from suffering from future drainage or compaction problems, both of which can result in expensive repairs. Just as with your home, your asphalt driveway's foundation is the key to its longevity.

Keep these tips in mind when looking for asphalt services near you.