Has your concrete slab dropped, tilted, or developed an uneven surface? Slab lifting (also called slab jacking or slab relevelling) is a targeted method for raising sunken concrete back to level — without ripping it out and starting again. It’s faster, less invasive, and significantly cheaper than slab replacement.

Through ADL Underpinning, you can connect with licensed contractors who carry out slab lifting for homes, commercial properties, and outdoor areas across Adelaide. Whether it’s a garage floor, driveway, patio, warehouse slab, or house slab that’s settled, this page covers how slab lifting works and whether it’s right for your situation.

What Is Slab Lifting?

Slab lifting is the process of raising a sunken concrete slab back to its original level by injecting material beneath it. The injected material fills voids under the slab, then generates controlled upward pressure to lift the concrete back into position.

There are two main slab lifting methods:

Polyurethane foam injection — expanding structural resin is injected through small holes in the slab. This is the modern, preferred method for most residential and commercial work. The foam expands rapidly, lifts the slab, and cures within minutes. Related to resin injection underpinning but specifically focused on slab levelling
Mudjacking (cement slurry) — a cement-based slurry is pumped under the slab through larger holes. This traditional method is still used for heavy slabs and large-area work, though it’s largely been superseded by foam injection for residential jobs

What Causes Slabs to Sink in Adelaide?

Understanding why your slab has dropped helps determine the right fix:

Soil settlement — poorly compacted fill beneath the slab gradually consolidates, creating voids. Common in newer Adelaide suburbs in Playford, Onkaparinga, and Salisbury
Washout erosion — leaking plumbing, poor drainage, or stormwater runoff washes soil out from under the slab, leaving voids
Reactive clay shrinkage — Adelaide’s Keswick Clay shrinks dramatically in dry summers, pulling away from the underside of the slab. This is especially pronounced in Unley, Burnside, and other eastern/inner-south suburbs
Tree root activity — large trees extract moisture from the soil, causing localised shrinkage and settlement near the tree
Decomposing organic fill — some older Adelaide developments were built on fill containing organic material that decomposes over decades, creating voids

When Is Slab Lifting the Right Solution?

The slab is structurally sound but has dropped — the concrete itself isn’t cracked through or broken, it’s just sitting lower than it should be
Settlement is up to 50–100mm — slab lifting handles moderate drops well. Extreme settlement may require slab replacement or structural underpinning
You want to avoid demolition — removing and replacing a slab is expensive, disruptive, and generates significant waste. Slab lifting is the repair-first approach
Driveways, patios, and paths — these are ideal candidates because they’re accessible, often only need lifting in localised areas, and replacement would damage adjacent paving or landscaping
Garage and warehouse floors — trip hazards and drainage issues from uneven floors are a liability. Slab lifting resolves them quickly
Pool surrounds — settled pool copings and surrounds are a common Adelaide issue, especially on reactive clay

When Slab Lifting Won’t Solve the Problem

We’ll always be upfront about the limitations:

The slab is badly cracked or broken — if the concrete has fractured into multiple pieces, lifting one section will separate it further. Replacement or overlay may be needed
The cause is ongoing — if a leaking pipe is continuously washing away soil, lifting the slab without fixing the leak means it’ll drop again. We identify root causes before recommending treatment
Deep foundation failure — if the entire house foundation is moving due to deep clay reactivity, slab lifting treats the symptom. Screw piles or mass concrete underpinning would address the underlying cause
Load-bearing slab issues — for structural slabs that carry wall and roof loads, slab lifting alone may not be sufficient. A structural assessment will determine if underpinning is also needed

The Slab Lifting Process

Site assessment — we survey the slab with a laser level to map exactly where and how much it has dropped. We also assess the slab condition, identify the likely cause of settlement, and check for underground services
Hole drilling — small holes (typically 16–20mm for resin, 40–50mm for mudjacking) are drilled through the slab at calculated intervals in the affected area
Material injection — resin or slurry is injected under the slab through the holes. For resin injection, the material expands and begins lifting within seconds
Real-time monitoring — laser levels continuously track the slab’s response during injection. The operator controls the lift speed and height precisely
Hole patching — injection holes are sealed with quick-set mortar or concrete. The repairs are neat and barely visible

A typical residential slab lifting job in Adelaide takes 2–6 hours. The slab can be walked on immediately after resin injection, and driven on within 24 hours.

Slab Lifting Costs in Adelaide

Slab lifting is substantially cheaper than slab replacement. Typical costs:

Driveway or patio section (small area, 5–15m²): $1,500–$4,000
Garage floor or large patio (15–40m²): $4,000–$8,000
House slab section (partial lift, localised settlement): $5,000–$12,000
Commercial floor (warehouse, retail): $8,000–$25,000+

Compare this to slab replacement, which typically costs $150–$300 per square metre plus demolition and disposal — a 50m² slab replacement could easily exceed $15,000–$20,000.

For an estimate, try our cost calculator or request a free quote.

Slab Lifting vs Full Underpinning

It’s important to understand the distinction:

Slab lifting raises a slab that has settled due to soil voids, washout, or compaction issues. It treats the slab’s position relative to the ground beneath it
Underpinning strengthens and deepens the foundation system that supports the building’s structural loads. It’s a more fundamental intervention

Sometimes both are needed — underpinning to stabilise the foundation, followed by slab lifting to re-level internal floors or external slabs. We’ll assess your situation and recommend the right combination.

For a detailed breakdown, see our cost of underpinning guide.

Get Your Slab Assessed

A dropped slab is more than a cosmetic issue — it creates trip hazards, drainage problems, and can indicate underlying soil issues that will get worse with time. The fix is often simpler and cheaper than you’d expect.

Email us at chris@adlunderpinning.com with photos showing where the slab has dropped. We’ll review within 24 hours and advise whether slab lifting will solve the problem — or if a different approach is needed. No obligation, honest advice.

Slab Lifting Adelaide