What Causes a Concrete Slab to Sink?

Erosion can cause a walkway to sink, creating a tripping hazard.

Before repairing your sinking concrete, it's important to understand why the concrete has sunk to make sure it doesn't happen again. Most of the time, the culprit is the soil underneath the concrete slab.

Concrete is heavy, and when the soil underneath the concrete slab can't support its weight, the slab will sink. Concrete that is cracking or sinking will get worse over time. This causes safety concerns and can even cause structural damage to other parts of your home.

Continue reading to learn about the common causes of sinking concrete, or contact us to get a free estimate on concrete leveling in [territory].

Causes of concrete settlement

The soils underneath an outdoor concrete slab can fail to support the weight of the slab due to three main causes:

Soil shrinkage and expansion

Changes in the amount of moisture in the soil can affect the soil underneath your concrete slab. When the soil gets wet, it holds water and expands in size. This is especially true for clay soil. When the soil becomes dry, it begins to shrink, creating voids (or empty space) under the slab, resulting in uneven, cracked concrete.

Soil washout

Water from heavy rains and plumbing leaks can find its way underneath your concrete slab and wash away the soil that's supporting the concrete. As the soil gets washed away, this leaves voids under the slab. With nothing to support the weight of the concrete, the slab will begin to sink.

Poorly compacted soil

During installation of a concrete driveway, patio, sidewalk or foundation, if the new concrete is poured on top of loosely compacted soil, the slab is more likely to settle. As the fill soil underneath the concrete slab compresses and settles, this creates voids under the slab. With nothing supporting the slab, the concrete cracks and sinks.

Get a quote to repair your sunken concrete

Are you experiencing sinking concrete problems? We will assess your property to find out the cause of your sinking concrete and provide you with a free estimate for concrete leveling service. Whether it's your sidewalk, driveway, patio or garage floor, A NO Dealers can raise and level your sinking concrete using the proven PolyLevel® method.