How to Fix a Sinking Concrete Driveway

That dip in your driveway wasn't there last year. Now it's collecting water, and the crack at the edge is getting wider every season. A sinking concrete driveway is common in Sydney — especially on clay soil — but it doesn't mean you need a full replacement.

Here's what causes it, how serious it is, and your options to fix it.

What Causes Concrete to Sink?

• Clay soil movement — Sydney's clay soils swell when wet and shrink when dry, causing slabs to shift
• Poor compaction — if the ground wasn't properly compacted before pouring, the slab settles unevenly
• Tree roots — roots suck moisture from the soil, creating voids under the slab
• Water erosion — stormwater washing away sub-base material over time

When It's a Minor Issue

If the sunken area is less than 10mm and there are no cracks or trip hazards, it's mostly cosmetic. You can monitor it — it may not get worse. For drainage issues, extending a downpipe away from the driveway can help.

When to Call a Professional

Call a concreter if: the lip is 20mm+ high, there are trip hazards, water pools on the driveway, or cracks extend across the slab. These won't fix themselves and will get worse with Sydney's wet-dry cycle.

Your Fix Options

Option 1: Concrete Resurfacing — If the slab is structurally sound but uneven, a 15–20mm overlay can level the surface. Cost: around $60–$90 per m². Lasts 10–15 years with proper sealing.

Option 2: Concrete Grinding — For minor unevenness (under 10mm), grinding down the high spots can eliminate trip hazards. Cost: $30–$50 per m².

Option 3: Mudjacking / Slab Jacking — A slurry is pumped beneath the sunken slab to lift it back into place. Cost: $300–$600 per m² depending on access. Not always suitable for Sydney clay soils.

Option 4: Full Replacement — If the slab is badly cracked (structural cracks over 3mm wide), replacement is the only option. Cost: $80–$150 per m² depending on finish.

Bottom Line

Most sinking driveways can be resurfaced rather than replaced — saving thousands. Get a licensed concreter to assess it; most will inspect for free.