When you look at your driveway, do you see a smooth, even surface or do you see dips and bumps? Is the top of your driveway lower than the rest of the drive? Improper compaction during your home’s construction may be the cause.
During the housing construction boom of the 1980s, ’90s and up until the 2008 recession, builders – particularly those involved in large-scale projects – didn’t pay much attention when the excavator who dug the holes for the houses returned to back-fill around the foundation. Many excavators just put back the native soils they had dug up. In cold weather, the frozen dirt didn’t compact well at all; air pockets formed; the soil began compacting unevenly on its own when the ground thawed and rain and snow weighed it down.
Many homes were left with loosely-compacted soil around them, especially in the three feet of driveway leading up to the garage door. Over time, that area sank, while the rest of the driveway stayed in place.
Builders don’t like call-backs. They’ve wised up since the 2008 housing bust and now charge excavators for settlement repairs. Excavators have also begun using granular materials rather than native soils to backfill foundations. This helps eliminate air pockets. But thousands of homes still have uneven driveways.
Sometimes a driveway will sink when a utility line runs underneath it. The utility contractor may have dug a trench for gas or electric service and did a poor job of backfilling the trench.
How to tell if your driveway has sunk
Is the place where the sidewalk meets your driveway higher than the driveway? Do the landscaping and lawn look higher than the driveway? Is there a noticeable dip in front of the garage door?
Proper base compaction combats driveway sinking
Whether it’s new construction or a driveway replacement, J&W Asphalt works with just the top six inches of the ground beneath the driveway, with a 4-inch base and 2-inch layer of asphalt.
We use a large vibratory roller to flatten and compact the base. When the operator gets to the top of the drive, he’ll pause and run the compactor until the roller stops sinking. Next we take a plate compactor and run it across the top and bottom of the driveway to smooth and press the material further. Then we re-grade the entire driveway to make sure it’s even all the way through. We finish the base by running the rolling vibratory compactor again, and plate-compact it one more time.
Now the base is hard and the ground beneath it is stable. It’s time to apply the asphalt layer, which is also rolled and compacted. We use a static roller to take out any unsightly lines in the blacktop. With proper maintenance, it should last 20-30 years.