Balconies and how to stop hidden water damage before it’s too late

The real danger lies in how easily water damage goes unnoticed until it's too late. Small cracks, poor drainage and failed sealants allow moisture to seep in, slowly eroding materials and weakening the balcony’s structural integrity. What starts as a minor issue - such as peeling coatings or damp patches - can escalate into widespread deterioration, requiring extensive remediation or, in extreme cases, full balcony replacement. 
Proactive waterproofing solutions can prevent these issues, preserving balconies for decades while ensuring compliance with existing safety regulations and industry best practices. Each and every balcony is different, but without a robust waterproofing system, they all become vulnerable to a wide range of structural risks.
A good example of this would be a balcony with a concrete deck. Concrete is a porous material, meaning it absorbs water over time. When water seeps into the concrete slab, it can cause spalling - a process where moisture penetrates and expands, causing the concrete to crack or chip away. This in turn weakens the structural integrity of the balcony and can also lead to surface delamination, where layers of the concrete break apart.
Most balconies are reinforced with steel bars (rebar) for added strength. However, when water infiltrates concrete and reaches the rebar, it causes oxidation and rusting. As the steel corrodes, it expands, placing immense pressure on the surrounding concrete, leading to cracks and further deterioration. If left untreated, this can compromise the balcony’s load-bearing capacity making it unsafe.
In colder climates, water trapped within a balcony’s structure can also freeze during winter, which also puts pressure on the surrounding materials. As temperatures rise, the ice melts and contracts, creating a cycle that worsens cracks and weakens the structure. Over time, this freeze-thaw cycle can cause severe damage requiring expensive repairs.
Mould and mildew growth
Water ingress does not just affect structural elements - it also creates a perfect breeding ground for mould, mildew and fungi. Moist conditions allow these organisms to thrive, causing health risks for occupants and further weakening of building materials.
For balconies that incorporate wooden decking or structural elements, water exposure can lead to wood rot. Once wood absorbs moisture, it softens and becomes prone to fungal decay. In severe cases, rotting timber can make the balcony unsafe and could lead to total failure.
As already mentioned, one of the biggest challenges of water damage is that it often goes unnoticed until significant deterioration has already occurred. By the time visible signs appear, extensive repairs - or even complete balcony replacement - may be necessary.
Early signs of water damage will frequently include hairline cracks in the concrete or surface tiles, signs of efflorescence and peeling or bubbling paintwork. Other warning signs include soft or rotting wood decking, water stains on the underside of the balcony, and rust streaks near railings or structural supports. Ignoring these early warning signs can lead to significant financial consequences. In extreme cases, neglected balconies are known to have collapsed, causing property damage, injuries and legal liabilities.
The importance of proper waterproofing
The best way to prevent water damage is by installing an effective waterproofing system from the outset. Whether it’s a new build or a refurbishment, choosing the right waterproofing solution can save building owners from costly repairs and will ensure the balcony remains safe and durable.
Seamless liquid-applied membranes offer one of the best waterproofing solutions available. Unlike traditional waterproofing methods that rely on sheet membranes (which can be prone to seams and overlaps), liquid-applied systems create a fully bonded, seamless barrier against water penetration. Products like Proteus Pro-BW® Plus provide a rapid-curing, UV-stable, skid-resistant solution that effectively protects balconies. It is also BBA certified to last up to 25 years and has the added advantage of being a cold applied system. Traditional waterproofing methods often involve hot works, which pose fire risks during installation. Cold-applied solutions eliminate this hazard, making them safer for both contractors and the building’s occupants.
By their very nature, balcony surfaces are also exposed to direct sunlight, which can cause some waterproofing systems to degrade or discolour over time. Choosing a UV-stable and colourfast system, like Proteus Pro-BW® Plus, ensures long-term protection without compromising aesthetics.
Another advantage of a liquid applied system is its resilience, because buildings will naturally expand and contract due to temperature changes. A high-quality waterproofing system must be flexible enough to accommodate structural movement without cracking or failing. Equally as important, waterproofing should also enhance overall safety. For instance, a skid-inhibiting surface prevents slips and falls, making the balcony safer for residents and visitors.
In summary, we can see that water damage is the ‘invisible enemy’ - one that can silently compromise the safety and integrity of balconies. The cost of neglecting waterproofing far outweighs the worthwhile investment in a high-quality system. By taking a proactive approach - using advanced, liquid-applied membranes like Proteus Pro-BW® Plus - property owners can safeguard their balcony structures against moisture-related deterioration for many more years to come.