Causes of Uneven Concrete Surfaces
Concrete surfaces, such as sidewalks and patios, may become uneven for one of two main reasons:
1. The concrete pavement has sunken due to unstable base or material warping
2. The concrete pavement has been pushed up by tree roots
Why you should repair uneven concrete surfaces
Uneven pavement should be fixed immediately to avoid trip hazards. People can be seriously hurt and may choose to take legal action against you for negligence.
The good news is that you have options.
The first is to grind down the pavement to create a flat, and properly graded, surface. This will not address sub-base or tree root problems and should not be considered a long-term solution in those cases.
The more appropriate solution is to remove and replace the concrete slab. In doing so, you can address the cause of the problem. The subgrade may need to be replaced and properly compacted, or the tree roots may need to be trimmed/contained.
Prevention of Uneven Concrete Surfaces
Cracks in the concrete pavement allow water into the sub-grade, which is a cause of concrete faulting (breaking at the joint) and settling. These cracks should be sealed before they get too big.