How Does Polyurethane Foam Lift Concrete?

Updated: Apr 8, 2020

As a kid growing up, I loved when the sidewalk made a ramp that I could jump my bike over.

As a business and homeowner, I was unaware just how much liability I had with concrete cracks, uneven joints creating trip hazards and just how unsightly unlevel concrete really is.

Replacing is just way too expensive, so we just kept our fingers crossed. Then I heard about foam concrete lifting and leveling and began to do my research and decided it was time to fix the problem once and for all.

Concrete Mudjacking vs. Foam Concrete Lifting

The initial technology utilized “mud” to jack the concrete up and while effective, it is disruptive, messy and not necessarily the best long-term solution. As the industry

evolved, the most successful competition for “mud” jacking was polyurethane foam technology. Polyurethane foam developed in the early 1960’s began to take a large foothold in numerous industries including insulation, roofing and just about everything that has a foam pad or cushion in it.

As the chemistry advanced, the applications for polyurethane foam grew dramatically. As the equipment technology caught up with the chemical technology, polyurethane foam began to be used in lieu of “mud” jacking for concrete lifting and leveling.

How Does Foam Concrete Lifting Work?

At its core, polyurethane is a two-component fluid material made up of a A-side and B-side.

The materials are pumped to a proportioner that heats and pressurizes the material to a 1:1 ratio, then it is pumped through a heated hose to the application gun where the two materials are mixed and begin to become polyurethane foam.

The two chemicals begin to react, increase in volume 30-40 times their original mass and develop a foam. This development of the foam is what lifts concrete.

What to Expect from a Polyurethane Foam Lift Concrete Appointment

A contractor who specializes in lifting and leveling concrete will have all the specialty equipment to properly process the polyurethane foam including:

  • Proportioner

  • Air Compressor

  • Generator

  • Foam Hose

  • Application Gun

  • Ancillary Tools Necessary to Work with Concrete

The process begins with a detailed assessment of the area of concern to ensure that lifting and leveling is appropriate, an estimate is generated, and a contract executed.


Once on-site, the contractor will strategically drill 5/8” diameter holes into the areas that need lifted and leveled. Multiple injection holes are required even for the smallest applications.

Port Installation

Plastic application ports will be installed into the drilled holes, and the application gun will be attached to the plastic ports, this is when the injection of the polyurethane foam can begin.

Foam Installation

Once the valve on the gun is actuated, the polyurethane foam enters the underside of the concrete and begins to spread out in a 3’ diameter circle.

The chemical reaction of the A and B side begins, and the foam increases in volume 30-40 times its original mass. The reaction and growth of the foam is what causes the concrete slab to lift. There are primary holes that develop the lift and secondary holes that are used to fill the void that is created adjacent to the “pillows” that are created through the lifting process. Without filling the voids, the concrete can be compromised or prone to additional cracking as there would be areas of the slab that are cantilevered without the proper substrate support.

Concrete Lifting

The foam pushes against the substrate and since the resistance of the substrate is greater than the resistance of the concrete, the slab begins to raise. It is through experience and thorough understanding of construction methods that the technician can inject the appropriate amount of material to perfectly raise and level the sunken concrete.

Overall the process is a simple and quick solution to removing your liability of trip hazards, increase the appearance of your property and most likely keep that pesky kid from jumping his bike in front of your house all day.

What are your next steps?

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