structural elements
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‘Every building or structure needs waterproofing – which in the long term is the most cost effective way to maintain its value’
Papworth Hospital used a dual system –SikaProof and Watertight Concrete
The benefits of a layered approach
The right choice of waterproofing for below ground structures can help avoid the financial implications of water ingress. Alex Burman of Sika looks at the options for architects and specifiers.
W
ith the primary cause of building failure being water ingress, the importance of developing a robust waterproofing strategy is vital to the
longevity of any building. Faced with the consequences of failure from business dis-
ruption to operational delays, loss of rent to disputes costs, the best defence is to get the specification right first time with an appropriate and robust waterproofing solution. But are speci- fiers best advised to take a single system approach or is an inte- grated, dual system the way to reduce risk and ensure a dry internal environment? When designing a below ground waterproofing specifica-
tion, it is important to first understand the terms of internal use and external effects on the structure. External effects vary from one structure to the next, from the type of soil to water table level and the type of water table. With this information, it is crucial that the below ground structure is fit for the future and prepared for water – whether it’s present or not. The recommendations given in BS 8102:2009 provide the
specifier with an outline of the three different waterproofing methods and include Type A – external or internal “tanking” typically using a membrane or cementitious render system; Type B – integral protection using an appropriate concrete mix design and admixtures providing a watertight barrier; and Type C – an internal drainage membrane (or water management) that collects and disposes of water that enters the structure. The complexity of so many construction projects, or when
the assessed risks are high, has led to specifiers adopting a more integrated approach, one where different solutions are combined and used to their strengths, to create a highly robust waterproofing strategy.
The right combination
The British Standard suggests consideration be given to the use of dual systems in projects where the assessed risks or the consequences of failure are too high. This approach to, say, a multi-million pound inner city development could see the
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