Most asphalt parking lot damage is only surface deep, which means repairs are quick and inexpensive. There is one type of failure that is much more severe. This is called base failure and it affects the very foundation of your lot.
Causes of Base Failure
The base of a parking lot is made of heavily compacted earth and gravel. The idea is that it will drain any moisture that makes its way underneath the paving, but it won't have room to settle or shift. This way, the paving over the base stays level and doesn't develop cracks from a shifting base.
Over time, though, the base can fail. Earth movement and shifting soils are some of the most common causes. There doesn't have to be an earthquake, either. Some soils are simply more prone to shifting, while other shift due to earth movement caused by nearby construction or drilling. Age increases the chances of failure, as water incursion becomes more common as the entire lot gets older.
Signs of Developing Issues
The signs of a failing base are usually obvious. The lot may sink in spots as voids begin to form beneath the paving. Cracks are also more likely to occur. Alligator cracks, which are a network of interconnecting cracks, often form on the surface of a lot with a failing base. There may also be uneven cracks, where one side of the crack sits higher than the other side due to uneven shifting of the base below.
Potholes and rut formation become more pronounced as the base gives out. This is in part due to the fact that standing water is more likely to occur on an unevenly settling lot, which leads to potholes. Once the potholes are deep enough to reach the base material, then water incursion can further degrade both the asphalt and the base materials.
Repairs and Solutions
Repair isn't usually possible once a base begins to fail, unless the damage is highly localized and the cause is from poor drainage. In this case, your contractor may be able to cut out some paving, re-compact the base, and install a drain before repaving. The drain prevents future issues.
Otherwise, the best solution is a full lot replacement. Your paving crew will remove the entire paved surface and then they will rebuild the base before paving the lot again. Additional drains and perimeter supports may be installed to prevent failure in the future, as well.
Contact a parking lot paving contractor if you suspect issues with the base of your paving.