What We Fix
Sunken Concrete Slabs
Relevel sunken concrete floor slabs — walk on it the same day. Driveways, paths, and pool surrounds too.
- Free assessment · 1–2 day repair · 20-year warranty
- Structural Engineers · Licensed Builders · Skilled Technicians
Trustpilot
GoogleWhat We Fix
Sunken Concrete Slabs
Relevel sunken concrete floor slabs — walk on it the same day. Driveways, paths, and pool surrounds too.
- Free quote · 1–2 day repair · 20-year warranty
- Structural Engineers · Licensed Builders · Skilled Technicians
Sunken Concrete Slabs
Relevel sunken concrete floor slabs — walk on it the same day. Driveways, paths, and pool surrounds too.
- Free structural assessment with a fixed-price quote
- No jackhammers, no tiles ripped up — most jobs done in hours
- 20-year product and workmanship warranty
Structural Engineers · Licensed Builders · Skilled Technicians
TrustpilotGoogleWhy is my concrete floor sinking — and can it be fixed without ripping it up?
Concrete floor slabs sink. It happens gradually — a slope you didn't notice until a door started sticking, a gap that opened at the skirting, a crack that appeared across the tiles. The slab hasn't broken. The ground beneath it has moved.
Most people assume the only fix is to jackhammer the floor, rip up the tiles, dig out the ground, recompact, repour, and wait for it to cure. Weeks of work. House unliveable. But here's what 15,000+ jobs have taught us: the concrete is almost never the problem. The ground underneath is. Fix the ground, and the slab goes back where it belongs.
The signs below will help you work out what's happening beneath your floor — and whether it can be relevelled without replacing it.
What are the symptoms of sunken concrete slabs?
Some signs are obvious. Others show up as problems you didn’t connect to the floor slab. Here’s what to look for — and why it’s happening.
Sloping or Uneven Floor
Place a ball on the floor. If it rolls, the slab has dropped on one side. You might feel it underfoot — a lean toward one corner, a slope across the room. Furniture wobbles. A spirit level confirms what your feet already told you. The most common cause is reactive clay — soil that swells when it’s wet and shrinks when it dries. Each weather cycle shifts the ground beneath the slab a little further. If the slope has appeared gradually, the ground is still moving.
Doors Sticking or Not Closing
A door that used to close fine and now drags, jams, or swings open on its own. The door isn’t the problem — the floor beneath it has shifted. When a slab drops unevenly, the door frame goes with it. If multiple doors in the same area are affected, the slab has moved significantly. Poor compaction during construction is a common driver — the filled side of the site settles, the cut side doesn’t, and the floor slopes toward the fill.
Gaps at Skirting Boards
A gap between the bottom of the skirting and the floor that wasn’t there before. The skirting is fixed to the wall. The floor has dropped away from it. Run your finger along the base — if the gap is wider at one end than the other, the slab has tilted rather than dropped evenly. Water runoff from poor drainage or leaking downpipes washes fine particles out of the soil beneath the slab, leaving voids. The concrete drops into the gap.
Cracked Floor Slab or Tiles
Cracks running through floor tiles, or visible cracks in an exposed concrete floor. Concrete doesn’t bend — when the ground beneath it drops away, the slab spans an unsupported gap and cracks. Tree roots growing under slabs are a common culprit: when the tree is removed or the roots die back, the space they occupied becomes a void. If the cracks are getting wider, the void beneath is getting bigger.
A Hidden Plumbing Leak
A leaking pipe you can’t see. Water mains, sewer lines, and stormwater drains run beneath floor slabs — when one cracks or disconnects, water saturates the soil for months before anyone notices. The ground softens, loses its bearing capacity, and the slab sinks into it. If your water bill has crept up unexpectedly, a leak under the slab is worth investigating. Fix the water source first, or the floor will just sink again.
Sunken Driveway, Garage Floor, or Outdoor Slabs
The driveway has dropped away from the garage, or the garage floor slopes toward the roller door. Water pooling on paths instead of draining. A pool surround pulling away from the coping. The ground beneath outdoor concrete is vulnerable to the same forces — reactive clay, poor compaction, water erosion. If it’s happening outside, the same thing may be happening beneath your floor.
How to spot a sunken concrete floor
How to fix sunken concrete floors
Non-Invasive. Laser-Monitored. Guaranteed.
No Jackhammers. No Tiles Ripped Up. Walk on It Today.
Concrete relevelling, also known as slab jacking, lifts your floor back towards level through coin-sized holes — no jackhammers, no tiles ripped up, no concrete trucks. As the foundation relevels, you'll notice doors closing again, furniture sitting flat, and the slope underfoot disappearing. Most jobs are done in a few hours, not weeks.
Slab replacement works — but it means jackhammering the floor, ripping up tiles, digging out the ground, recompacting, repouring, and weeks of curing. Here's what 15,000+ jobs have taught us: the concrete almost never needs replacing. The ground beneath it does.
GeoPoly™ SJ120 — a controlled-expansion resin — is injected through the access holes directly into the ground beneath the slab. The resin fills the voids, compacts the weakened soil, and expands with precision to lift the concrete back towards level. Laser levelling equipment monitors every millimetre of movement in real time. The resin hardens within minutes — tougher than the original ground.
Not sure if your floor slab can be relevelled? That's exactly what the free assessment answers.
What to expect
A step-by-step guide of how the slab jacking process works — from assessment to completion.
Step 1Free Structural Assessment
A Buildfix engineer checks floor levels, inspects the slab, and identifies what’s causing the sinking — whether it’s reactive clay, soil washout, poor compaction, or a plumbing leak beneath the concrete. A tailored GeoPoly™ relevelling plan is designed on the spot.
Step 2Get Your Quote and Book
A complete quote package arrives — detailed drawings, repair method statement, and a fixed-price quote. The price you see is the price you pay. When you’re ready, book through the online portal and suitable dates are organised for the work.
Step 3GeoPoly™ Injection
Small holes are drilled through the slab at precise intervals. GeoPoly™ resin is injected directly into the ground beneath the concrete — filling voids, compacting weakened soil, and creating a stable base for the slab to sit on. No tiles are removed. No concrete is broken up.
Step 4Lift, Level, and Verify
The slab is gradually lifted back towards level using laser-monitored precision. Digital sensors track every millimetre of movement in real time. No self-levelling cement is poured on top. The engineer confirms the results before the team leaves.
Step 5Receive Your Warranty
Your 20-year product and workmanship warranty arrives via email with the Completion Package — a job report covering the work, materials, and images.
See the difference
Actual GeoPoly™ slab jacking — before and after.
Instant results.
Guaranteed to last.
The benefits of fixing sunken concrete slabs with GeoPoly™.
Sunken concrete doesn’t need breaking up and repouring. GeoPoly™ is injected beneath the slab to fill voids, compact the soil, and lift it back towards level. You’ll see the sunken slab rising in real time — monitored with laser equipment to millimetre precision.
Not sure if it's subsidence? Get your home assessed for free — we'll explain exactly what's going on and what can be done.
Real homes. Real results.
15,000+ homes and structures repaired. Want to see real Buildfix slab jacking? Browse a few below.
HomeownerLoganholme, QLD
Sinking Garage Lifted 45mm — Harleys and All
A garage sinking for over two decades on poorly prepared soil. GeoPoly™ lifted the slab 45mm in under four hours — the Harleys never moved.
HomeownerStrathfield, NSW
Heritage Home Repaired Twice, Same Team
When new cracks appeared in this 150-year-old Strathfield home, the owner didn’t hesitate — they called Buildfix again. Buildfix had already fixed the front of the house years earlier. This time, the team tackled the rear.
CommercialBrisbane CBD, QLD
Roma Street Parkland Walkways Relevelled
Sunken stairs, walkways, and bikeways across 16 hectares of public parkland. Brisbane City Council has used Buildfix to relevel affected sections.
HomeownerRaceview, QLD
Dining Floor Relevelled — Not a Tile Broken
A sinking dining room floor on reactive black soil — relevelled in one day through 1cm holes in the grout joints, without breaking a single tile.
HomeownerOrmeau, QLD
Pool Surround Relevelled — No Tiles Lifted
Sections of the tiled pool surround had sunk, creating uneven edges and a daily safety hazard around water. Relevelled without pulling up a single tile.
CommercialRunaway Bay, QLD
Sunken Tennis Court Lifted 100mm
A tennis court at a residential complex had dropped 100mm — a genuine trip hazard. GeoPoly™ lifted it back to level without reconstructing the surface.
“All of the Buildfix team have been easy to communicate with. Everyone was punctual and communicated arrival times well ahead of arrival.”
Scott HolmesMelbourne, VIC
“All of the Buildfix team have been easy to communicate with. Everyone was punctual and communicated arrival times well ahead of arrival.”
Scott HolmesMelbourne, VIC
“All of the Buildfix team have been easy to communicate with. Everyone was punctual and communicated arrival times well ahead of arrival.”
Scott HolmesMelbourne, VIC
“All of the Buildfix team have been easy to communicate with. Everyone was punctual and communicated arrival times well ahead of arrival.”
Scott HolmesMelbourne, VIC
Questions?
Our team is here to answer any questions you may have Monday – Friday 8am to 4pm AEST. Give us a call on 1300 854 115.
