10 March 2022 - 10:56, by , in Balcony Waterproofing, No comments


The body corporate on this site understands the importance of identifying signs of concrete deterioration as well as the importance of being proactive in getting the situation assessed and repaired before it got worse. If the spalling concrete had been left untreated, sections of concrete could in the future break loose and fall off the balcony’s edge, potentially hurting someone or other property.

The challenge is that the small signs of concrete cancer one can see often hide more extensive damage than is apparent on the surface.


  • Flaking, crumbling, spalling, expanding concrete
  • Rust Stains leaking out of the concrete
  • Bubbling, blistering, plating of concrete render
  • Leaks in overhead concrete surfaces
  • Rusting and exposed reinforcement pushing concrete so that it cracks and becomes loose


Unfortunately, the problem is likely to be much more extensive than symptoms on the concrete surface suggest. As steel rusts, it can expand up to eight times its original size, causing the surrounding concrete to break away. Once established, the rusting will spread along the reinforcing in each direction. It is impossible to know the full extent of the damage until all unsound concrete is chiselled away.


Concrete cancer on balcony edge before works - Waterstop Solutions

Image: Concrete cancer on the balcony edge.

Concrete cancer is influenced by several factors, such as proximity to the coast and a built-up environment; degree of steel reinforcement covered by concrete; the presence of differential metals; coating system quality and density; inadequate waterproofing; building defects cracking; joint and penetration detailing; and preventative maintenance.

One of the most common places to find corrosion of reinforcement steel is in columns and beams due to a lack of concrete covers to protect the steel and/or poor-quality concrete. Concrete cancer is also common in basements, underground car parks, and flat concrete roofs and balconies.

The main cause of premature deterioration, premature ageing, and durability issues in concrete is corrosion of reinforcing steel or other embedded metals. Concrete cancer can happen in many areas of a concrete structure, so it is a good idea to regularly look out for tell-tale signs so that it can be remedied before it gets severe and becomes a serious problem and starts affecting the strength and structural integrity of the building.

As soon as possible, cracks and holes should be adequately sealed to prevent spalling. Cracks can be repaired by injecting epoxy or polyurethane resins into cracks in order to fill them. A protective coating, a penetrative concrete sealer, or a waterproof membrane will protect against moisture, salts, and chemical attacks.


Our extensive experience on major civil projects has afforded Waterstop Solutions opportunities to design with industry-leading engineers and tackle some of the most complex concrete repair challenges imaginable in the built environment. Using this knowledge, we can provide you with a range of options to best meet your project criteria.

The typical method of concrete cancer repair follows a process of:


  1. Break out unsound concrete and expose reinforcing steel until sound concrete and clean non-corroded steel reinforcing are found.
  2. Saw cut repair zone perimeter to eliminate feather edges.
  3. The concrete around the reinforcing steel is chiselled away. Prepare substrates including removing any corrosion. Reinstate steel and/or add more as deemed necessary.
  4. After completion of material removal, concrete primers and rust inhibitor to the steel are applied before reinstating with a high build shrinkage compensated repair mortar. Formwork may be erected to close the cavity prior to installing the repair products.
  5. For further long-term protection, we also recommend a membrane coating system. Install a heavy-duty modified acrylic membrane in multiple layers as a moisture barrier primer system. The primer system will assist in preventing bubbling or blistering, which is highly likely if the remedial waterproofing application is not performed, which could otherwise affect the durability of the system.
  6. We recommend that treatment of concrete cancer should incorporate proper weather/waterproofing membrane or protective coating or the repair risks being a temporary solution. Install correct waterproofing or protective coatings that are designed to protect surfaces that are exposed to rainfall, wind and/or sea spray. Ensure that the waterproof membrane or the protective coating system is detailed to all penetrations and junctions.

After the concrete cancer has been repaired, preventative measures must be taken to prevent recurrence. It is recommended to implement a maintenance program customized for the environment the building is exposed to, including dedicated inspections. Regular maintenance checks will help identify any problems in the earliest stages, which will also contribute to enhancing the service life and reducing the life cycle cost of concrete structures.

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