Should Gravel Be Allowed to Settle Before Laying the Asphalt Driveway?

A thick layer of gravel is used before pouring an asphalt driveway.

Necessary Compaction

A compactor roller is used to press down the gravel completely.

Once the area for an asphalt driveway has been prepared, a layer of gravel 8- to 12-inches thick is put down. This gravel subgrade is compacted with an asphalt roller to press the gravel down until it reaches about 95-percent compaction, which means there is a little amount of space between the stones and it is almost 100-percent solid.

Natural Settlement

Cracked asphalt can result from improperly compacted gravel.

If the layer of gravel is put down and allowed to settle on its own, and the asphalt is placed over the gravel layer, the gravel will not conform to the required thickness and continues to settle and shift, which results in cracks and uneven asphalt pavement.

Bottom Line

According to the Washington Asphalt Pavement Association, the gravel layer should be compacted to a sufficient density in order to maintain the integrity of and prevent erosion of the asphalt material used on the driveway.

References

• Washington Asphalt Pavement Association: Surface Preparation
• National Asphalt Pavement Association: Construction Guidelines