Polyurethane Foam Concrete Lifting: How Polyjacking Works

Concrete slabs sink for boring reasons. Water from a downspout washes away the soil underneath. Backfill next to a foundation was never compacted. Clay shrinks in a drought. The slab loses support, settles, cracks and becomes a trip hazard — or tilts back toward the house and sends water into the basement.

Tearing it out and pouring new concrete is one fix. Lifting it back into place with expanding polyurethane foam is often a faster, cleaner, less expensive one.

How polyjacking works

Why polyurethane instead of mud?

Mudjacking — pumping a cement-and-soil slurry under the slab — has been around for decades and still works. Polyurethane has a few advantages that have made it the more common choice for flatwork:

The weight difference matters more than it looks. If soft soil caused the settlement in the first place, pumping a heavy slurry under the slab adds load to that same soil. Foam adds very little.

Lifting foam vs. insulation foam

Lifting foams are a different formulation from spray insulation. They are designed to be structural, closed-cell and hydrophobic, with controlled reaction times so the operator can lift in small increments. ArmorThane’s ArmorFoam Lift 200 is a 2.50 pcf water-blown, closed-cell slab-jacking foam aimed at residential patios, driveways and sidewalks; Lift 300 is a denser 3.75 pcf formulation for heavier commercial and industrial slabs.

Good candidates — and bad ones

A good add-on for foam contractors

Concrete lifting uses a smaller, simpler setup than a full insulation rig, and the jobs are short — often a few hours. For applicators already handling two-component polyurethanes, it is a natural second line of work, and homeowners who call about a sinking walk often need insulation, too.