What are the Base and Sub-Base Layers in Driveway Installations?

To the untrained eye, a driveway might just look like a slab of asphalt or concrete. But anyone who has experience with driveway installation knows there is much more to it. In fact, two of the most important structural features of a driveway — the sub-base and base layers — are completely invisible when the job is finished. Without these layers, though, you are bound to have a weak driveway that won’t last more than a year or two without severe cracking and damage.

Read on to find out more about the important base and sub-base layers — and how to choose the right paving specialist for your new driveway.

Sub-Base Layers

A sub-base layer of a driveway is the main load-bearing layer that sits atop your subgrade. Sub-base is made of aggregate material — and while the thickness of the sub-base layer will depend on your driveway and vehicle, a few centimeters alone will greatly improve the strength and durability of your driveway. A well-installed and compacted sub-base will help prevent those dreaded ruts in the pavement where your tires most often pass over.

In addition to helping bear the load of your vehicle, a sub-base is also important for drainage. Visible damage to driveways occurs when water doesn’t drain properly, leading to cracking. A sub-base layer will ensure that moisture drains away from the asphalt, keeping your top layer intact.

In paving jobs that will only be used by pedestrians it is possible to avoid installing a sub-base layer, but for any job where a vehicle will be using the driveway, this is an essential step that shouldn’t be skipped.

Base Layers

Atop the sub-base layer, most asphalt driveways will require a base layer, also made of aggregate material. The base layer is typically thicker than the sub-base layer, and often formed from a finer grade of aggregate.

Both the base and sub-base layers require mechanical compaction to reach their full strength. Depending on the size of your driveway, contractors might use heavy rollers or plate compactors for the job. Ideally, the compacted based and sub-base layers should sit for up to a week before the asphalt is poured. This waiting process allows them to fully settle.

Finding a Qualified Driveway Installation Specialist

There’s no doubt that installing a driveway is more complicated and requires more sophisticated equipment than one might think. Once you start to understand the intricacies of the process, the need for a truly skilled and qualified specialist becomes clear. How do you go about finding one? Of the asphalt, concrete and pavement specialists in your area, narrow the field to three or four contractors with good online reputations, solid reviews, and a track record of successful driveway installations. Years and experience and continual investment in the best new equipment are also essential traits to make sure your driveway is installed the right way. When proper care and attention is given to the invisible layers of your installation, you can expect it to last for years to come with no major repairs.