Concrete patching is the most common concrete repair, from chipped steps to spalled slab edges. Done properly it lasts for years. Done badly it falls out within a season, sometimes taking more concrete with it.
When a patch works
- Surface chips, scaling and small broken edges.
- Small holes and voids in non-structural concrete.
- Damage where the cause is gone, such as an impact.
When a patch is the wrong fix
- Corroding steel underneath: patching over concrete cancer traps the rust, and the patch pops off. See concrete spalling.
- Moving cracks from ground movement or overloading.
- Large structural damage to beams, columns or suspended slabs, which needs engineering.
- Water still getting in from above.
Repair materials
- Polymer-modified cementitious repair mortars: the most common choice for general patching.
- Epoxy mortars: high strength and fast curing for thin or heavily trafficked repairs.
- Fairing coats: thin finishing layers to smooth the surface.
How to patch concrete properly
- Remove all loose and damaged concrete back to sound material.
- Cut the edges square with a saw, so the patch is not feathered to nothing at the edges.
- Treat any exposed steel if found, or the repair becomes a concrete cancer repair.
- Clean and prepare the surface: dust-free, and damp or primed as the product requires.
- Apply in layers within the product's thickness limits, compacting well.
- Cure properly, protecting from sun, wind and traffic.
Why concrete patches fail
- Feathered edges that crack and lift.
- Patching over dusty or contaminated surfaces.
- Rusting steel left behind the patch.
- The wrong product, or too thick in one layer.
- No curing in hot or windy weather.
Colour matching
Patches rarely match old concrete exactly. Where looks matter, a coating or resurfacing over the area gives a uniform finish.
Concrete repairs in Sydney
We patch what can be patched and tell you honestly when it needs proper remediation. See our concrete repair service or call 0415 840 500.
Frequently asked questions
Can you patch concrete cancer?
Not with a simple patch. The damaged concrete must be removed and the corroding steel treated, or the patch will fail.
What is the best product for patching concrete?
Polymer-modified repair mortars suit most general patching; epoxy mortars suit thin, high-strength or fast-cure repairs.
Why does my concrete patch keep falling out?
Usually feathered edges, poor surface preparation, rusting steel underneath, or no curing.
