Erickson Foundation Supportworks | August 26, 2015

YouTube // Concrete & Masonry, Glues, Sealants, Coatings

How to Repair a Sinking Concrete Slab


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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Thank you for your article on PolyLEVEL. Could you elaborate on the foam's impact both short and long-term on the environment? 

Niles Erickson's picture

Thanks for your question Sarah. The PolyLEVEL product is environmentally friendly, as the chemicals which react with each other to form the high density foam do not react with the soil. It does not release harmful chemicals into the surrounding soil. Compared to alternative methods for lifting cement patios, slabs or similar, the impact on the environment is less as it does not require heavy equipment, is less labor intensive, and provides a quick clean up with no excess material lying around.

I have a concrete slab that sunk about 4 inches toward the house. I now have a moist wall in the basement. What can be done and is this process sensitive to low temperatures.

Niles Erickson's picture

Rick, thank you for your question/comment.

PolyLEVEL is a perfect solution for sunken slabs like you described. As the slab has settled toward the wall, an increasing amount of rainwater is being directed into the crack between the slab and the foundation.  This results in further erosion and settlement, as well as a large amount of water pooling under the slab, and saturating the foundation wall.  In a situation like this, we will use the PolyLEVEL to lift the slab along the house so that it will shed water away from the foundation wall. Because PolyLEVEL is a closed cell structural foam, water cannot penetrate it.  Once the slab has been lifted and stabilized, we can also apply our Nexus Pro sealant to the joint between the slab and the foundation to prevent further erosion and to ensure that water cannot get through to penetrate the wall. In regards to low temperatures, the PolyLEVEL system cannot be installed while there is frost effecting the soils at the point of injection underneath the concrete slab.

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