Concrete Cancer
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What is Concrete Cancer?

You have heard the term concrete cancer, but what does it actually mean? Concrete cancer is the layman’s term for moisture related deterioration of a concrete component. In building terminology it is known as spalling damage or technically alkali-silica reaction. Spalling damage can be both unsightly and structurally devastating if not addressed.

Evidence Of Concrete Cancer

Concrete cancer or spalling damage is not something that just occurs in other countries around the world, it is actually very common in the homes I inspect throughout south-east Queensland everyday. Below are just a few of the common areas where we regularly find evidence of spalling damage.


Concrete CancerOne of the most common areas to see spalling damage is in the concrete stumps supporting your house. If adequate drainage is not maintained around your house, excessive moisture within the sub floor area can be absorbed by the concrete stumps. That retained moisture causes a reaction with the concrete and exposes the steel within the concrete stumps to premature corrosion. The expanding rusting steel blows apart the concrete stumps eventually rendering them unsound and not capable of supporting the load above. When inspecting your concrete stumps you may initially notice some hairline cracking particularly around the edges of the concrete stumps. Eventually these hairline cracks will lead to more substantial cracking and whole sections of concrete breaking away exposing the rusting steel. These stumps will subsequently require replacement.

Patio Slab

We would recommend regular inspection to the underside of your concrete patio slab where access is possible. Quite often moisture passing through the concrete slab will contribute to spalling damage resulting in concrete breaking away from the underside of your patio slab exposing the rusting steel reinforcement. Repairing waterproof membranes across the surface of the slab may help prevent excessive moisture penetration into the concrete slab. Subsequent patching of the concrete cancer from underneath may help prevent further deterioration and prolong the lifespan of your patio. If the damage has become excessive it will be necessary for an engineer to evaluate the patio structure to determine whether it could be saved or whether replacement is required.

Slab Edge Moisture

Concrete CancerAnother common cause of concrete cancer (spalling damage) is slab edge moisture penetration. This is quite often most noticeable in a garage where the lack of floor coverings exposes a white powder known as effluorescence and obvious slab moisture down the edge of the garage floor. The slab edge moisture is often the result of poor allotment drainage around the walls or a damaged or incorrectly installed vapour barrier around the edge of the garage slab. Whilst damage to the concrete slab due to this type of moisture penetration is usually slow it can eventually cause cracking and surface deterioration to the concrete slab.

Retaining Walls

To avoid decay damage and termite attack many people opt for concrete sleeper retaining walls. The downside is that they often succumb to concrete cancer. If the horizontal or vertical support sleepers are substantially compromised due to the level of spalling damage, then the wall will require replacement. Unfortunately replacing a retaining wall can be a very costly process.

These are just a few of the typical examples of concrete cancer that we detect during building inspections throughout Brisbane on a regular basis. This damage can however occur to almost any concrete structure. To avoid potential costly rectification works we would strongly recommend obtaining a building inspection prior to purchase of any property.




About Andrew Mackintosh

Andrew Mackintosh has been answering home inspection questions in the greater Brisbane area since 1995. He has personally carried out over 20,000 building inspections and is a licensed builder and licensed building inspector, Member of Queensland Master Builders Association & Institute of Building Consultants. Being the business owner and the inspector, Andrew is passionate about providing clients with excellent customer service, value for money, honest, unbiased, thorough inspection and reporting in a professional and timely manner to allow clients to make informed decisions when purchasing property.

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