Why Is Driveway or Sidewalk Sinking?

You’ve noticed that portions of your sidewalk or driveway (or porch, or pool deck, or any other concrete slab around your house) has started to sink. The slab is cracking, and the elevation change on either side of the crack is posing a tripping hazard. But why is your slab sinking?

The root of the problem likely lies in the soil beneath it, including when the root of the problem is literally a root.

Causes of Sinking Concrete Slabs

Soil Not Properly Compacted

Concrete is heavy. If the soil beneath the sinking slab isn’t properly compacted, it won’t be strong enough to support the weight of the concrete without the slab sinking.

Erosion

Erosion can create voids under concrete slabs. Those voids then act as weak points, with those portions of the slab sinking. This differential settlement causes cracking and tripping hazards.

Shrink-Swell Cycle

Some soils, especially clay, have significant shrink/swell cycles. Depending on the condition of the soil when the concrete was laid, the soil shrinking as it dries could lead to settlement or the soil expanding when it is wet could lead to heaving.

Tree Roots

As trees grow, the roots grow, and sometimes grow under concrete slabs. During the growing stage, the roots are more likely to cause heaving than settlement or sinking. Mature trees, depending upon soil type, can draw enough water in through their roots to dry out the surrounding soil. The shrinkage from this can cause settlement in some cases. If a tree dies or it cut down, the decomposing roots can create voids or patches of poorly compacted soil, causing the slab to sink.

How We Repair Sinking Slabs

If the sinking slab is caused by poorly compacted soil or voids beneath the slab, we have the solution: concrete lifting with polyurethane foam. We pump the expanding foam beneath the slab. As it expands, the foam fills any subsurface voids and compacts the surrounding soil from within. It then hydraulically lifts the slab back to level from underneath.

Read more about concrete leveling.

Contact Us To Learn More About Our Concrete Leveling Services in Southern California

Foundations on the Level proudly serves San Diego and Orange counties in California. If you live within our service area and would like to learn more about how we can lift your sunken concrete slab, contact us today.