First of all, it is important to establish the fact that most structural concrete is water-tight, meaning to say that rain water, below-ground water and water vapour are not able to penetrate a bare concrete even without waterproofing. This is further proven and enforced during construction by a structural water ponding test prior to installation of waterproofing systems. If a newly casted concrete structure is unable to pass a 48-hour water ponding test, it is required to undergo structural repair such as pressure grouting using suitable grouts such as polyurethane (PU), epoxy, hydrophobic urethanes, acrylic resins and many more. Only after the structural water ponding test is passed will the installation of waterproofing system be carried out. Therefore, it is important to understand that even without waterproofing membrane, a concrete structure in Singapore will not face any water intrusion problem.
Next, after a concrete structure is certified to be water-tight, contractors will then install waterproofing systems onto the wet area surfaces. Some example of wet area includes: bathroom, kitchen, balcony, swimming pool, basement and roof terrace. Each wet area faces different natural conditions, such as degree of direct sunlight received, surface temperatures and etc, different wet areas require specialized waterproofing systems built specially for each area. For example, a roof terrace’s waterproofing system is required to be extra elastic due to its daily expansion and contraction resulting from the weather. Every waterproofing membrane has its own strengths and weaknesses, it is important to engage an experienced and knowledgeable waterproofing specialist contractor because they need to understand which system is suitable for which area. I have personally seen too many general contractors who installed a waterproofing system at a place which is completely unsuitable and as a result, the waterproofing system gets damaged and fails within a year from installation.
It is now crucial to understand why water leakage occurs at your reinforced concrete (R.C.) structures. Concrete expands when it is hot and contracts when it is cold, like any other material which undergoes daily expansion and contraction, it is common for concrete to crack. When a crack forms on your R.C. structure, the concrete is no longer water-tight. Luckily for us there is still the waterproofing system in place to bridge the crack in the concrete and continues to prevent water from seeping into the concrete. A water leakage will only occur when both the R.C. structure and the waterproofing membrane has cracked and gave way. It is important to note that despite waterproofing membranes being elastic and crack-bridging, the extent which a waterproofing membrane can be stretched is limited. Hence once the crack gets too big, the waterproofing membrane will give way and tear. In this scenario, the concrete structure is exposed to direct water intrusion and this is when water seepage/leakage occurs.
When you face a water seepage or leakage on your R.C. structures, it is safe to conclude that both your R.C. structure and waterproofing membrane has cracked. How then should we carry out the repair? There are many ways to repair a structural water seepage and leakage. First, we can strengthen and repair the R.C. structure’s cracks and voids by doing high pressure injection grouting. This injection grouting involves high pressure using machines that can inject the resin into the concrete and seal up all the cracks and voids. Once the cracks and voids are all sealed up, the R.C. structure is back to being water tight and water seepage/leakage will stop. Another way to repair this water seepage/leakage problem is to hack and remove the existing damaged waterproofing system and re-install a new waterproofing system. However, please note that by only re-installing a new waterproofing system and not repairing using injection grouting, the waterproofing system is not sufficiently strong. A sound R.C. structure without cracks can last a longer time than a superficial waterproofing system which may crack and tear really quickly. By doing structural repair, we can be more assured that future water seepage/leakage will be less likely to occur because the concrete structure is now strong and sound and this will last a long time.
There are many methods to solve a water leakage or seepage problem and it is important to consult a waterproofing specialist contractor whom are more knowledgeable and experienced in the waterproofing industry for their expert opinion. There does not exist a one system fits all waterproofing system that can be used everywhere, each and every water leakage and seepage problem requires specific and tailored repair method in order to resolve.