Learn / remediation guide
Concrete cancer in Sydney apartments
If the concrete is cracking, rusting or falling away from a balcony or facade, the damage is usually bigger than the patch you can see.
Concrete cancer is the name people use when reinforced concrete starts breaking down and exposing rusted steel. Once the steel expands, the concrete around it cracks and falls away. On apartment buildings and strata assets, that can show up on balconies, slab edges, parapets, staircases and car park structures.
Sydney gets this problem a lot because many buildings are exposed to moisture, coastal air and older detailing that was never intended to last forever without maintenance. The visible damage is only part of the story — the steel behind it is usually what needs attention.
The right response is not cosmetic patching. It is a proper assessment, a repair scope that addresses the steel and concrete, and then a way to keep water out so it does not come back.
Common warning signs
- Rust staining running out of cracks or slab edges.
- Concrete pieces spalling or dropping off balconies and facades.
- Exposed or bulging reinforcement steel.
- Hollow sounding concrete when tapped.
- Cracks that keep coming back after a patch.
What a proper repair needs
- Identify the source of water and corrosion.
- Remove damaged concrete back to sound material.
- Treat, clean or replace corroded reinforcement steel.
- Rebuild the section with the right repair system and finish.
How to deal with it properly
Find the spalling and rust staining
Look for cracked concrete, rust marks, delamination, exposed steel and chunks falling from slab edges or balcony undersides.
Check how far the corrosion has spread
The visible damage is often only the bit you can see. The repair has to account for the steel and concrete beyond the surface patch.
Stop the water getting back in
Without sealing the source — drainage, waterproofing, joints or coating — the problem usually comes back.
Repair the concrete and the steel properly
A proper job includes breaking out damaged concrete, treating or replacing corroded reinforcement, then reinstating the structure.
If you’re seeing spalling, get it checked
On apartment buildings, delay usually makes the repair bigger and more expensive. An early assessment is the cheapest way to keep the structure under control.