Issues beneath the asphalt can cause part of your paving to sink. New asphalt may simply warp and sink into the low spot, while older asphalt isn't as pliable and it may crack and break away from the main paving as an area sinks. Fortunately, it's often possible to fix a sunken area without fully replacing it.
1. Determine the Cause
Asphalt sinks when something compromises the base beneath the paving. The most common causes are poor drainage or a poorly constructed base. Lack of proper drainage can cause erosion underneath the base, which creates a void that the asphalt sinks into. A poorly constructed base is more prone to this erosion or it can give out due to shifting soils.
2. Remove the Damage
Damage removal and cause determination are often done at the same time, since your contractor may need to lift out the sunken asphalt before they can be sure of the cause. In most cases, your contractor will cut around the low area and then lift out the sunken slabs of asphalt. Then the base will be assessed for damage and erosion. Base materials may need to be removed as well so the spot can be reconstructed.
3. Rebuild the Base
If the base is in good condition but sunken, your contractor may just need to build it back up and compact it well. For paving bases that have suffered erosion or were poorly constructed, the damaged area is removed and rebuilt so that it is better compacted and more resistant to movement and sinking in the future. Base repairs are the key to avoiding additional sinking in the future.
4. Add Some Drainage
Since drainage problems play at least a small part in most instances of sunken asphalt, adding more drainage to the area before repaving can prevent future issues. The type of drainage installed depends on where the paving is and how to best route the water. One method is to install a perforated drain pipe under the paving and embedded in the base materials. Another option is to install grated drains that are routed into the storm sewer system.
5. Resurface the Paving
The final step is to put down fresh asphalt. The edges of the asphalt surrounding the repair are usually milled down so that the patch can overlap the old asphalt and bond to it. If you don't like the look of the patched area, you can have the rest of the paved area resurfaced at the same time. Resurfacing is the process of laying a thin layer of asphalt over old asphalt, which will blend patched areas so they are less noticeable.
Contact an asphalt service in your area if you notice sinking on your paving.