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Sinking or Washed Out Concrete Sidewalk

By Chris Sullivan – ChemSystems, Inc.

Question:

We have a stamped concrete sidewalk that is settling in an area near one of our downspouts, probably due to erosion of the subbase underneath the slab. We plan to redirect the downspout, but how do we relevel the slab without causing damage?

Answer:

When it comes to lifting and or releveling decorative concrete slabs or concrete foundation slabs that have sunken or subsided due to washout or deterioration of the subbase, you have two options. The first is mudjacking, or slabjacking. This process has been used for decades, and involves pumping a flowable (high-slump) cement-based liquid fill under the slab through holes to lift the concrete back into place (see How Slabjacking Is Done). Once the concrete slabs are level and back in place, the holes are capped off, and the fill material cures to form a solid concrete subbase.

A newer trend is to lift settled concrete using a polymer-modified material instead of a cement-based fill. The polymer material flows easier and solidifies faster, reducing the labor and time required to lift the slab. It also is more resistant to future washout and environmental deterioration. The URETEK Method is one example.

Both of these methods are proven, and reputable contractors often provide multiyear warrantees on the materials and workmanship. Get estimates from several professionals who do this type of work to determine the best option for your particular situation.