Skip to content
POLYJACKING.CAA HAUSE site / Canada

Guide

How polyurethane lifting foam works

Lifting foams are two-part polyurethanes mixed at the injection gun. The reaction produces a closed-cell foam that expands into voids and hardens.

Conceptual section showing a settled concrete slab over a voidA blue-grey dashed datum marks the adjoining slab height. The central concrete panel sits lower above a void in the sub-base. Orange arrows indicate the potential lift direction; injection is considered only after assessing the slab and cause.FIG. 01 / SUBSURFACE SECTIONN.T.S.REFERENCE DATUM ─ 0001 / ADJACENT SLAB02 / SETTLED PANEL03 / SUB-BASE + SOIL04 / VOIDASSESS CAUSE BEFORE LIFTINGSECTION A—A
01 / Adjacent slab02 / Settled panel03 / Sub-base and soil04 / Void under panel
Conceptual illustration / not to scale / not a real project

Two components

An isocyanate and a polyol blend are pumped separately and mixed at the gun. Once mixed, they react and expand. Reaction time and expansion depend on the formulation and temperature.

Densities and purposes

Manufacturers offer foams of different densities and reaction speeds. Some are formulated for lifting, others for filling voids or stabilizing soil. The right product depends on the job.

Questions to ask a contractor

  • Which product will you use, and why?
  • Can I see the manufacturer’s data sheet?
  • How will you control the lift and avoid over-injection?
  • How will you keep foam out of drains and utilities?

Environmental notes

Cured foams are generally considered inert, but products differ. Manufacturer safety data sheets describe handling and properties.

Next step: an assessment

Photos help, but the only reliable way to decide whether a slab can be lifted is an on-site look at the concrete, the drainage and the likely cause of settlement. Submit a request and the HAUSE intake team will review it and confirm whether a suitable contractor is available in your area.

Conceptual illustration

What happens under a settled slab

Water and loose fill leave a void; foam injected through small holes fills it and lifts the slab.

  1. 1 · Void forms

    Water, erosion or poorly compacted fill leaves a gap under part of the slab.

  2. 2 · Slab drops

    Unsupported concrete sinks, creating trip edges and slope toward the house.

  3. 3 · Small holes

    The contractor drills small injection holes at planned points.

  4. 4 · Foam fills & lifts

    Expanding polyurethane fills the void and raises the slab in controlled steps.

Text version
  1. 1 · Void forms: Water, erosion or poorly compacted fill leaves a gap under part of the slab.
  2. 2 · Slab drops: Unsupported concrete sinks, creating trip edges and slope toward the house.
  3. 3 · Small holes: The contractor drills small injection holes at planned points.
  4. 4 · Foam fills & lifts: Expanding polyurethane fills the void and raises the slab in controlled steps.
Conceptual illustration · © PolyJacking.ca · HAUSE. Not to scale; not a photo of real work.

More in the visual guides · try the slab self-check.

Have a settled slab?

Describe it, add photos if you have them, and the HAUSE intake team will review your request and confirm whether a suitable contractor is available near you.

Request an assessment
Request assessment