For many older apartment buildings in Sydney, particularly in coastal suburbs like Bondi, there’s a ticking time bomb hidden beneath the flooring. This issue, known as concrete spalling or “concrete cancer,” is often accelerated by an old flooring material called magnesite. What is Magnesite and Why is it a Problem? Magnesite flooring was a popular choice for floor levelling and soundproofing in apartments built between the 1920s and 1980s. While it served its purpose well at the time, we now know it has a critical flaw: it's highly porous and absorbs moisture like a sponge. When magnesite gets wet, it releases corrosive chloride ions. These chlorides then migrate into the concrete slab below and attack the steel reinforcement bars, causing them to rust and expand. This expansion is what puts immense pressure on the surrounding concrete, leading to cracks, flaking, and crumbling—the tell-tale signs of concrete spalling. This process can severely compromise a building's structural integrity. The Bondi Coastal Factor: Salt Air Acceleration In a suburb like Bondi, the problem is intensified. The beautiful coastal location with its fresh sea breeze brings a hidden danger: salt air. The high levels of airborne salts and humidity common in beachside environments provide a constant source of moisture and corrosive agents. This accelerates the chemical reaction within the magnesite, making concrete spalling a more urgent issue for Bondi property owners and strata committees. The combination of ageing magnesite flooring and the continuous exposure to salt-laden air creates a perfect storm for structural decay. What might be a slow process elsewhere becomes a rapidly deteriorating problem in Bondi. Recognising the Signs of Concrete Spalling It's crucial for property owners to be proactive. Look out for these warning signs: Visible cracks or flaking in concrete surfaces. Bubbling or lifting of paint or render. Rust-coloured stains seeping from the concrete. Unusual moisture or dampness on floors, especially near balconies or wet areas. A musty, damp odour. If you notice any of these symptoms, it's a sign that the underlying issue is worsening and requires immediate attention. The Solution: Urgent Magnesite Removal and Repairs Delaying action only leads to more extensive and costly repairs. The recommended approach is a multi-step process that needs to be carried out by a remedial building expert: Professional Inspection: A specialist will assess the extent of the damage and confirm the presence of magnesite. Magnesite Removal: The old flooring must be carefully and completely stripped away. Concrete Spalling Repairs: Damaged concrete is meticulously repaired, and new reinforcement is often installed. Prevention: A new, non-porous and waterproof flooring system is installed to prevent future moisture issues. Taking these steps now can protect your investment and ensure the long-term safety and value of your Bondi property. This is a common and serious issue in many older Sydney apartments, so it's best to act quickly. This article was inspired by content from Elyment's blog and other industry sources. Key Takeaways Magnesite flooring, common in older Bondi apartments, absorbs moisture and causes steel reinforcement to corrode. Bondi's salt-laden air accelerates this decay, leading to urgent concrete spalling. Look for signs like rust stains, cracks, and bubbling paint. Urgent removal and professional repair are essential to prevent costly structural damage. Connect with us on X: @ElymentGroup or visit our website for more information at elyment.com.au.