Cracks in a concrete driveway or path are common across Australia, especially where hot summers, heavy rain, tree roots and ground movement put pressure on slabs. Some cracks are cosmetic, while others can point to ongoing movement or drainage issues that need attention. The key is to work out what type of crack you have, then choose the right repair method before the damage gets worse.
If the crack is small and stable, many homeowners can handle the repair with a few basic tools and a concrete patching product from Bunnings or Mitre 10. If the slab is lifting, sinking, badly broken or repeatedly cracking, it may be time to call a qualified concreter.
First, Work Out What Kind Of Crack It Is
Not every crack needs the same fix. Before you repair anything, look closely at the width, length and location of the damage. Also check whether the crack changes over time, or whether one side is higher than the other.
- Hairline cracks: Fine surface cracks that are often cosmetic.
- Wider static cracks: Cracks that stay the same size and do not move.
- Movement cracks: Cracks that keep widening, or where one side rises or sinks.
- Spalling or broken edges: Areas where the concrete has flaked, chipped or broken away.
If the concrete has large sections lifting, major sinking, or signs of serious subsidence, patching alone will not solve it. That kind of movement usually needs professional assessment.
How To Repair Small, Stable Cracks
For fine to moderate cracks that are not moving, a surface repair is usually the best approach. This helps stop water getting in, which is especially important in wet weather or where the slab gets full sun and then cools quickly at night.
What You’ll Need
- Wire brush or stiff broom
- Vacuum or blower
- Concrete crack filler, flexible sealant or patching compound
- Putty knife or trowel
- Safety glasses and gloves
- Masking tape if you want cleaner edges
Step-By-Step
- Clean the crack thoroughly. Remove dirt, loose concrete, weeds and old filler.
- Open the crack slightly if needed. For some fillers, a shallow V-shaped groove helps the product bond better.
- Remove dust. Vacuum the crack or blow it out so the repair material can stick properly.
- Apply the filler. Use a flexible concrete crack filler for narrow cracks, or a patching compound for slightly larger gaps.
- Smooth the surface. Level it with a putty knife or trowel so it sits flush with the slab.
- Let it cure. Keep vehicles, foot traffic and water off the area until the product has cured as directed.
For driveway cracks, choose a product designed for external concrete and movement. A rigid filler can fail again if the slab expands and contracts in the heat.
When A Repair Needs More Than Patching
Some cracks are signs of a bigger problem. If you see one or more of the issues below, simple filler may only be a temporary fix:
- Cracks wider than a hairline that keep opening up
- Sections that rock underfoot or under a vehicle
- Water pooling near the crack after rain
- Tree roots pushing the slab up
- Multiple cracks across the same area
- Edges that are crumbling or badly spalled
In these cases, a concreter may recommend slab lifting, cutting and resealing joints, replacing a damaged section, or improving drainage. If the problem is related to ground movement, it is better to deal with the cause than to keep patching the surface.
Preventing More Cracks Later
Once the repair is complete, a few simple maintenance steps can help protect the slab and extend its life.
- Keep water away. Make sure garden beds, downpipes and paving do not direct water under the slab.
- Seal the surface if appropriate. A concrete sealer can help reduce water penetration and staining.
- Trim tree roots carefully. If roots are affecting the slab, get advice before cutting them back.
- Avoid heavy point loads. Do not park very heavy vehicles on a slab that is already damaged.
- Check drainage after storms. Poor runoff is a common reason concrete keeps cracking.
Australian conditions can be harsh on outdoor concrete. Strong UV, heat, expansion and sudden rain all take a toll, so it is worth checking your driveway or path every few months, especially after summer or heavy weather.
Repair Products Versus Professional Help
| Situation | DIY Repair | Call A Concreter |
|---|---|---|
| Hairline surface crack | Yes, with concrete filler or sealant | Usually not needed |
| Moderate crack that is not moving | Often yes, if you prep it properly | Helpful if you want a neat finish |
| Crack with height difference | Not ideal | Yes |
| Sinking, lifting or rocking slab | No | Yes |
| Repeated cracking after repair | Not recommended | Yes |
Always follow product instructions and use suitable personal protective equipment. If your repair involves cutting, jackhammering, grinding or working near services, take extra care and check for underground utilities before you start. Some related work can be regulated under state and territory rules, so if there is any doubt, speak with a licensed professional. Electrical, gas and certain plumbing work must always be done by a licensed tradesperson in Australia.
If your driveway or path is badly damaged, a qualified concreter can assess whether the slab can be repaired, resurfaced or should be replaced. For broader home improvement guidance, you can also compare information through Building or renovating across the Tasman? Our sister site Trade Directory NZ covers the same topics for New Zealand homeowners.