How to Repair a Sinking Concrete Slab

August 26, 2015


Repairing a cracked and sinking concrete pool patio and it's adjoining concrete slab walkway by injecting high-density foam under it


Concrete slabs sink and settle because of bad base preparation. It is not the slab's fault.

My company recently repaired a cracked and sunken slab surrounding a swimming pool. We use a two-part closed cell foam to float the slab up to the correct height. 


Inject the foam and then seal the cracks

First, we drill through the slab at key locations and insert ports into the holes. Next, we pump in a polymer foam which consists of two separate liquids that are combined at the injection nozzle to trigger a chemical reaction that turns the blended ingredients into expanding, high-density foam.

The foam expands and raises the slab up to the correct height. The foam may fill some of the cracks in the slab, but the surface of the crack and the port holes are completed with a caulking that is great for concrete—NP1.


The foam is structural

This system is not strictly for patios and pool slabs, it can be used for industrial slabs and roads as well. By adjusting the density and expansive force of the 2-part foam the lifting force can be adjusted. Fine-tuning the chemical reaction causes the foam to expand more or less. In some cases it is used to lift, level and stabilize roadways and airport runways.

The system is called PolyLEVEL; it is a product of Foundation Supportworks Inc, and they have contractors/dealers throughout the country.  We are the primary dealer for New Hampshire and northern Massachusetts.


—Niles Erikson works with Erickson Construction and Erikson Foundation Supportworks in Hudson, NH

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