You may have heard of prostate cancer, breast cancer and lung cancer but rarely does the public know about Concrete Cancer. What is it? How do buildings get it? What does it mean to the value of my property?
Concrete Cancer is the term given to the failure of concrete. Another name its known by is concrete spalling.
There are 3 causes;
1. Insufficient cover of concrete over the steel reinforcement may allow water to penetrate , reaching the steel reinforcement and ultimately causing rust. Once rust forms it expands and "blow off" the concrete cover and ultimately exposing the steel reinforcement which accelerates the process.
2. The use or presence of chloride based compounds along with a reduction in alkaline will cause a similar corrosion or rusting of the steel reinforcement.
3. Sometimes the cement component in the concrete is too alkaline, it reacts with carbon dioxide in the atmosphere and star shaped cracks appear which allows rain or water to enter. In cold temperatures the water freezes in the cracks causing the concrete surface to spall.
TREATMENT
Concrete Cancer is treatable on a case by case basis. Repairs usually require the exposed steel to be cleaned of rust or replaced with a new cement mortar cover or epoxy based mortar.
The cost is expensive and requires the full proper waterproofing to allow a long term solution.
In some case extreme cases, occupants are required to vacate the building for considerable time whist major works are undertaken.
OCCURENCE
The occurrence of Concrete Cancer in Australia is high where liquid membranes are still commonly used. Liquid membranes are often used inappropriately, and lead to water penetrating into the concrete.
It is often associated with builders cost cutting by using inappropriate materials and not applying sufficient cover of concrete around the steel reinforcement.
RISKS FOR BUYERS
Properties close to coast lines, beaches and the like are more susceptible to Concrete Cancer due to exposure to saltwater winds or ocean spray. That does not mean inland properties are exempt from this issue..
High density development have a strong history of cost cutting measures which has lead to concrete cancer.
City office building from the 1960s to the early 1980s with extensive concrete also have a higher than average risk.
Many strata developments have had to raise special levies to cover such one off repairs. Many buyers make the mistake of inspecting the subject unit but not conducting a full inspection of the whole building including common areas.
The negative impact of value can be greater than the cost of the Special Levy or repairs. Some prospective purchaser will simply not be interested in a building that has "building defects". For example. A unit worth $600,000 unaffected suddenly has a Special Levy of $75,000. The market value is likely to be less than $525,000. A further reduction of 10 to 20% can be attributed to reduced saleability.
An independent buyers agent and a reputable valuer with local experience may be able to find out anecdotally of potential liabilities and special levies, even if not disclosed in a strata report. Seldom do agents and owners disclose such potential problems.
When making an offer, it is important to factor in such costs for rectifications and an allowance for reduced marketability.