Stamping out rising damp saves money

Although only a few centimetres of rain fall on the UAE each year, water damage can shorten the life expectancy of any building and cost clients money. Even so, local developers have been slow when it comes to implementing comprehensive watertight solutions. But now times are changing... Construction Week reports on waterproofing.

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By  Colin Foreman Published  June 14, 2004

Stamping out rising damp saves money|~|Waterproofbody.jpg|~|Old one storey buildings that used to make up most of Dubai did not pose many waterproofing headaches. |~|When it comes to making structures watertight the requirements have changed over the years. The old one-storey villas, which used to dominate much of Dubai just needed a few water outlets on the roof to allow water run-off on the odd occasion that it rained, but today’s complex modern structures, such as banks and airports, require custom-designed watertight solutions. “I remember a few years ago I went to a government housing project in the interior and I felt there was something odd about the roof, it was only when I got home that I realised they didn’t have rain water outlets,” says Ranbir Khanna, business line manager watertight systems, MBT Middle East part of the Degussa Group. “People now have to look at watertight systems seriously, particularly, for example, in sensitive environments such as electronic product showrooms,” he adds. The water table level is of primary importance, especially in the coastal regions, where in many cases it is quite high. The unabated rate of urban development in the UAE has made the effective use of space a premium. Consequently, newer buildings commonly have basement parking and other services as standard. “These subterranean structures need to be fully protected by first class waterproofing materials,” says Salim Shuhaibar, managing partner, Duproof. Although the waterproofing material is undoubtedly important, it is how the whole watertight system behaves that is important. “If someone were to say that the passive membrane is supposed to do everything they would be wrong. The quality of the concrete is almost as important, as is how you treat the joints. All concrete structures have joints and this is the first place that a leak will manifest itself because water will always find the easiest way through into the structure,” says Khanna. If the watertight system is unsatisfactory, water will be able to penetrate the structure and compromise its integrity. If buildings are not properly protected at this fundamental level it will significantly reduce the life expectancy of the structure. “Water will penetrate the concrete structure and corrode the steel reinforcement causing it to break down and expand. [This] will then cause the concrete to crack; and the cost of repairing the concrete can be tremendous,” says Shuhaibar. The type of building is also an important consideration when devising a waterproof solution because different buildings require different levels of protection. For example, a basement car park would be treated in a different way to a bank vault, a museum, a hospital, or an airport. Sensitive structures, which can’t tolerate any water ingress, require more comprehensive solutions than car parks where a certain amount of ingress is often tolerated. However, no system is perfect, and eventually nature will have its way and water will find a way through. “You can reduce the risk of water affecting a structure by using proprietary engineered watertight systems but never disturb the equilibrium of nature,” says Khanna. There are a number of shocks that a structure and its watertight system endure which can result in cracks and water ingress. The first is when the dewatering system is switched off and water comes back to level resettling the structure. The second is when the increased loading put onto the structure during construction, which again causes a degree of movement. The third is when the AC systems are switched on: causing a thermal shock that causes the concrete to cool down and contract. The fourth, and less significant effect is the loading that occurs when people and equipment move into the building. A further structural movement can happen when the environment changes and other structures are built nearby. “The water table levels for a building in an undeveloped area are insignificant, but as the area becomes developed, the water table can rise and it will become an issue,” says Khanna. Another important factor is humidity. In the summer months, relative humidity in the UAE can reach up to 95% or even 100%, making waterproofing a major consideration when putting up roofing structures and or laying concrete. “Concrete structures must be protected by damp-proofing properly. This is not just [with] the application of paints, but proper materials that actually penetrate the concrete preventing dampness from entering the structure,” explains Shuhaibar. When roofing, inverted roofing systems can be used that combine plasticity and elasticity by using the very technology to overcome any movements that the roof may go through. “Lightweight concretes that are used for roofing often move when they cure and this can create of hairline cracks and blow holes if a low quality waterproofing material is used,” warns Shuhaibar. Currently, the UAE construction industry isn’t following best practice waterproofing techniques that have been designed in more mature markets, such as Europe or the US. “[Local] manufacturers do not follow the same code of practice as done in Europe. In many cases recycled plastic is mixed with bitumen that can lead to the bitumen and the plastic separating, which affects the life cycle of the building,” says Shuhaibar. “It is important to look at specifications, and select the right quality of materials that conform to international standards and use virgin material. What is the point of saving a few dirhams when it might compromise the quality of the product?” says Shuhaibar. Despite these concerns overall awareness in the market is improving. “Awareness has grown over the last two to three years as people realise that watertight systems are an essential component of construction and cannot be overlooked. With the advent of private investment in construction and the ever-increasing competition in the real estate market, durability of structures has become a fundamental requirement,” says Khanna. As the market has matured it has also learnt that piecemeal solutions are about 10 times more expensive in the long run, than installing a satisfactory system in the first place. Of the overall construction costs, a watertight system is normally less than 2% of the cost of a structure. In addition, once water penetrates a structure it is very difficult to be sure what is going on inside the structure. “Just because you can’t see the manifestation of a leak, doesn’t mean there isn’t a problem,” says Khanna. Inevitably water will penetrate the structure but it is the number of back-up systems that give the system longevity and durability. For a system to work well every component must be considered fully. This includes the membrane, the concrete, the pile heads, and service penetrations.||**||

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