Maintenance
Why Is My Concrete Driveway Cracking? Causes & Fixes (2026)
By Fraser Coast Concreting · 14 June 2026
Quick answer
Concrete driveways usually crack from shrinkage as the slab cures, missing or poorly placed control joints, reactive clay soil movement (common around Maryborough and the Fraser Coast), tree roots, heavy loads or poor mix and curing. Fine hairline cracks are usually cosmetic, while wide, uneven or lifting cracks can be structural and should be assessed.
A few fine cracks in a concrete driveway are normal and usually nothing to worry about. Wider or uneven cracks can point to something underneath. This guide explains why concrete cracks, how to tell cosmetic from structural, and what you can do to prevent and fix it.
Why concrete cracks: the common causes
- Shrinkage. As fresh concrete cures and dries, it shrinks slightly. This is the most common cause of fine cracks and is largely unavoidable, but it’s controlled with proper joints.
- No or poorly placed control joints. Control joints are the cut lines that tell the slab where to crack. Without enough of them, or if they’re cut too late or too shallow, the slab cracks where it likes.
- Reactive clay soil movement. Much of Maryborough and the Fraser Coast sits on reactive clay that swells when wet and shrinks when dry. That movement flexes the slab and can crack it, especially if it wasn’t engineered for the soil.
- Tree roots. Roots growing under a slab lift and crack it over time.
- Heavy loads. A domestic slab not built for trucks, caravans or heavy machinery can crack under the weight.
- Poor mix or curing. Too much water in the mix, or letting the slab dry too fast in the sun and wind, weakens it and invites cracks.
- Lack of reinforcement. Without adequate steel mesh, a slab has little to hold it together when it moves.
Cosmetic vs structural cracks
Not all cracks are equal. Here’s a rough guide.
| Crack type | Likely cause | Concern level |
|---|---|---|
| Fine hairline cracks | Surface shrinkage | Usually cosmetic |
| Thin cracks along joints | Normal jointing | Usually cosmetic |
| Wide cracks (3mm+) | Movement, load, soil | Worth assessing |
| Uneven / lifting cracks | Soil movement, roots, settlement | Possibly structural |
| Cracks with displacement | Slab failure or footing issue | Get it assessed |
If one side of a crack sits higher than the other, the crack is widening, or it runs across the whole slab, it’s worth having someone look at it rather than just patching over it.
How to prevent cracking
Most cracking is designed out before the pour. A well-built driveway includes:
- Properly spaced and timed control joints, cut at the right depth so the slab cracks neatly where intended
- Adequate reinforcement (steel mesh, and bar where needed) to hold the slab together through movement
- A solid, well-compacted base so the slab is fully supported
- Engineering for reactive soil where the ground demands it
- Correct curing, keeping the slab moist as it sets rather than letting it dry too fast in our coastal sun and wind
- A mix suited to the job, without excess water
This is exactly why base prep, jointing and curing are not the places to cut corners, particularly on Fraser Coast clay soils.
Why the local climate matters
Around Hervey Bay and Maryborough, slabs face strong sun, drying winds and big swings between the dry season and heavy wet-season rain. Those moisture swings drive reactive clay movement, and fast drying after a pour encourages shrinkage cracks. A slab that’s properly jointed, reinforced and cured copes with all of this far better.
Fixing and resurfacing options
What’s right depends on the crack:
- Cosmetic hairline cracks: often just left, or sealed to keep water out and tidy the look.
- Minor cracks: can be filled and sealed to stop water getting in and worsening them.
- Surface wear with sound slab underneath: resurfacing can give a fresh, like-new finish over the existing slab, often more affordable than replacement.
- Structural cracking or failed slabs: sometimes the slab needs sections replaced or a full re-pour. This is the case when movement, footing problems or load have damaged the slab itself.
The key is getting the cause right. Resurfacing over a slab that’s still actively moving will just crack again, so it’s worth having the cause assessed first.
Should I worry about my cracks? A quick self-check
You can get a reasonable first read on a crack before anyone visits. Run a finger or a coin across it and look closely:
- Width. Hairline cracks you can barely catch a fingernail in are almost always cosmetic. Cracks wider than about 3 mm deserve a closer look.
- Level. Sight along the crack. If both sides are flush, that’s reassuring. If one side has lifted or dropped, that points to movement below.
- Pattern. A single line near a joint is usually normal. A spider-web or map-cracking pattern across the surface can indicate a curing or mix issue, while a crack running clean across the whole slab suggests structural movement.
- Change over time. Mark the ends of the crack with a pencil and check in a few weeks. A crack that’s actively lengthening or widening is worth assessing sooner.
When in doubt, it’s cheap to have it looked at and expensive to ignore a structural problem.
What causes cracks specifically on the Fraser Coast?
A few local factors make cracking more likely here than in some other parts of Queensland:
- Reactive clay soils around Maryborough, parts of Hervey Bay and the wider Fraser Coast swell and shrink dramatically between the wet and dry seasons, flexing any slab that wasn’t engineered for it.
- Big seasonal moisture swings mean the ground under your driveway is rarely at a constant moisture level, so it’s always gently moving.
- Hot sun and drying winds can pull moisture out of fresh concrete too fast, encouraging shrinkage cracks if the slab isn’t cured properly.
- Heavy wet-season downpours can erode poorly compacted base material, leaving the slab unsupported in patches.
None of these are dealbreakers. They’re simply the reasons a properly engineered, jointed and cured slab matters so much in this region.
How control joints prevent cracking
Control joints are one of the most misunderstood parts of a driveway. Concrete is going to shrink as it cures, that’s a given. Control joints are deliberately weakened lines, cut or tooled into the slab, that give the shrinkage somewhere tidy to go. The slab cracks neatly along the bottom of the joint instead of randomly across the surface.
| Joint factor | Done well | Done poorly |
|---|---|---|
| Spacing | Regular, sized to slab thickness | Too far apart, slab cracks between |
| Depth | About a quarter of slab thickness | Too shallow to control the crack |
| Timing | Cut at the right time after the pour | Cut too late, slab already cracked |
Get the joints right and most shrinkage cracking simply disappears from view. Get them wrong and the slab decides for itself where to crack.
Can cracks be prevented entirely?
Not completely, and any concreter who promises a crack-free slab forever isn’t being straight with you. Fine shrinkage cracking is a natural property of concrete. What a good build does is control where and how it cracks, so it stays cosmetic rather than structural. Proper base prep, the right reinforcement, sensible joint placement, a suitable mix and careful curing are what keep cracks fine, hidden and harmless. That’s the realistic goal: not zero cracks, but no cracks that matter.
How are different cracks repaired?
The right repair depends entirely on the cause and severity. Here’s how the common options compare.
| Repair option | Best for | What’s involved |
|---|---|---|
| Crack sealing | Fine, stable hairline cracks | Clean and fill to keep water out and tidy the look |
| Crack injection / filling | Wider but stable cracks | Flexible filler to seal and stop water entry |
| Partial slab replacement | Localised structural damage | Cut out and re-pour the failed section |
| Resurfacing | Surface wear over a sound slab | New finish bonded over the existing slab |
| Full replacement | Failed or actively moving slabs | Remove and re-pour with correct engineering |
As a guide only. The key is matching the fix to the cause, which is why an assessment beats guessing.
Will the crack come back after repair?
That depends on whether the underlying cause has been dealt with. Sealing or filling a stable shrinkage crack usually holds well, because the slab isn’t going anywhere. But filling a crack caused by ongoing soil movement, tree roots or a footing problem is only a temporary patch. The slab will keep moving and the crack will reopen, often nearby. This is the single most important reason to identify the cause before choosing a repair. A good concreter will tell you honestly whether a quick fix will last or whether the real issue needs addressing first.
Should I be concerned about water in cracks?
It’s worth keeping water out, even of cosmetic cracks. Water that seeps into a crack can reach the steel reinforcement and the base below. Over time it can rust the steel and wash out or soften the base, both of which make a small problem bigger. On the Fraser Coast, where wet-season rain is heavy, sealing even minor cracks is cheap insurance against water finding its way in and accelerating wear. It’s one of the simplest pieces of driveway maintenance you can do.
Simple maintenance to keep cracks at bay
You can’t change how a slab was built, but you can look after it:
- Seal cracks early to keep water out before they worsen.
- Keep large trees in check and be mindful of roots heading toward the slab.
- Direct downpipes and run-off away from the slab edges so the base stays stable.
- Don’t overload a domestic slab with trucks or heavy machinery it wasn’t built for.
- Re-seal decorative finishes on schedule to protect the surface.
None of this is hard, and it goes a long way to keeping a sound driveway sound.
We repair and resurface driveways
If your driveway is cracking and you’re not sure whether it’s cosmetic or something more, Fraser Coast Concreting can assess it and recommend the right fix, whether that’s a simple repair, resurfacing or replacement. We work across Hervey Bay, Maryborough, Rainbow Beach and Tin Can Bay. Request a free quote here and we’ll take a look.