Most cracked driveways in Geelong are not the result of bad luck or a single heavy delivery truck. They are the ground underneath moving with the seasons, and the concrete telling you about it. This piece explains why that happens, which cracks you can live with, and the point at which patching stops making sense and replacement is the better spend.
The ground is doing the work, not the frost
In Britain, the usual villain for a broken drive is frost. Water gets into the surface, freezes, expands and spalls the top off, or frost heave lifts a poorly laid base. Geelong rarely gets the kind of hard, sustained freeze that does that. The movement here comes from the soil itself.
Much of the region west and north of the city sits on the volcanic basalt plains, and the soils that have weathered from that basalt are often heavy, dark clays. Reactive clay swells when it is wet and shrinks when it dries out. After a wet winter the ground can be noticeably higher than it is at the end of a long, dry summer, and that rise and fall is not even across a driveway. One side may be shaded and damp while the other bakes against a fence line. The slab is effectively being flexed every year.
Australian engineers classify sites by how reactive their soil is, from Class A (sand and rock, little movement) through S, M and H to E for extremely reactive ground, with P for problem sites. Plenty of Geelong suburbs fall in the M to H range, and some pockets are worse. If you have a soil report from when the house was built, it will state the class, and it is worth digging out before you talk to anyone about the driveway.
Tree roots and drainage make it worse
Trees add to the problem in two ways. Roots can physically lift a slab, which is easy to spot, but the less obvious damage comes from a large tree drawing moisture out of clay during summer. That localised drying causes the ground to shrink under one part of the drive, and the concrete cracks along the line where support drops away.
Water does the opposite. A downpipe that discharges onto the edge of the slab, a blocked stormwater pit or a garden bed watered heavily beside the drive all keep one strip of clay wetter than the rest. Before anyone quotes for new concrete, it is worth fixing whatever is feeding or starving the soil, or the new slab will go the same way.
Which cracks matter
Not every crack is a failure. Concrete shrinks as it cures, and fine hairline cracks are close to inevitable. Control joints, the straight grooves or saw cuts you see every few metres, exist precisely so that the concrete cracks there, in a neat line, rather than randomly across the panel. A crack running along a control joint is the joint doing its job.
| What you see | Likely cause | Usual response |
|---|---|---|
| Hairline cracks, no height difference | Normal shrinkage | Leave, or seal to keep water out |
| Crack along a control joint | Designed behaviour | Reseal the joint |
| Wide crack with one side higher | Soil movement or roots | Investigate the cause; patching rarely lasts |
| Several cracks, sunken or rocking panels | Lost support underneath | Replace the affected panels or the whole drive |
The key signal is displacement. Once one edge of a crack sits higher than the other, you have a trip hazard, a water path into the subgrade and a sign that the slab is no longer bearing evenly.
Patch or replace?
Patching suits cosmetic cracking on a slab that is otherwise sound and level. Flexible sealants and epoxy fillers keep water out and tidy the look, though they will never be invisible and they do not fix whatever is moving the ground.
Replacement becomes the better option when panels have dropped or tilted, when cracks keep reopening after repair, when the drive is old and was never reinforced, or when you are changing the layout anyway. You can usually replace individual panels between control joints rather than the full length, which keeps cost down if the damage is localised.
Because soils vary so much from street to street, local knowledge counts for a lot here. Reading through a regional firm’s information, such as geelongconcretedriveways.au, gives a sense of how Geelong contractors approach reactive ground before you start collecting quotes.
What a better replacement looks like
A new driveway on reactive clay should be specified for the ground, not just poured to habit. The points worth asking about are straightforward:
- Thickness: around 100 mm is common for cars, with more for heavier vehicles such as a caravan, boat trailer or campervan.
- Reinforcement: steel mesh placed at the right height in the slab, sitting on bar chairs rather than lying in the dirt.
- Subgrade: a compacted, well-prepared base, with soft spots dug out rather than covered over.
- Joints: control joints at sensible spacing and at changes in shape, plus expansion joints against the house and existing paths.
- Drainage: falls that move water off the slab and away from the edges, and downpipes connected properly to stormwater.
Work on the council land between your boundary and the road, the crossover, generally needs a permit from the City of Greater Geelong or the relevant shire, so check their requirements before the old drive is broken out.
Questions readers ask
Is a cracked driveway a problem when selling?
Minor cracking is common and buyers in the region expect it. Raised or sunken panels may be flagged on a building and pest report as a trip hazard, which can come up in negotiation.
Will a thicker slab stop it cracking?
Thickness and mesh help the slab resist movement and hold cracks tight, but nothing guarantees a crack-free drive on reactive clay. Good joints and drainage matter just as much.
Can I pour a new section myself?
Owners can generally do small concrete jobs on their own land, but matching levels, joints and finish is harder than it looks. Anything touching the council crossover needs the council’s approval first.