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structural elements
detailing of joints and penetrations, as well as achieving a “crack free” concrete are important. Design and execution should also consider a limited crack width, correct mix design, an effective curing regime and pour sequencing in order to avoid shrinkage or cracking. It’s important for specifiers to be aware that an integral
waterproofing system is not suitable for an application such as a podium deck, where thermal movement and shrinkage may lead to cracking beyond the normally accepted levels. Additional measures are necessary where, for example, Radon is an issue. Even ‘crack free’ concrete will contain micro-cracks which are a potential path for Radon and Methane to enter the building. The Sika Watertight Concrete System is an example of a
guaranteed system which complies with Type B construction, using advanced admixtures added to the concrete to prevent water penetration. Carefully selected waterstops for construc- tion and movement joints complete the system, producing a waterproof structure.
Water management system
Where it isn’t possible to keep water out completely, water management is an effective solution. Cavity drainage membranes work on the principle of allowing water to con- tinue to penetrate the structure, and then managing the water and diverting it into a suitable drainage point. These Type C systems effectively allow water ingress, so
The Riverside retail scheme in Chelmsford benefits from a dual system from Sika
application of tanking and watertight concrete to provide an impenetrable structure. The most widely used waterproofing system in the UK and
many other countries are external waterproofing membranes. Often they perform a dual purpose – waterproofing as well as offering an additional protection measure (APM) for the concrete where aggressive ground conditions prevail. In the case of projects which combine both refurbishment
and new build, different systems could be specified for dif- ferent applications – for example, render systems for retro installation as part of the refurbishment and watertight con- crete and/or membranes for the new build element. Membrane strength, durability and performance are key
considerations in the specification process of waterproofing in heavy civil engineering applications or aggressive ground conditions. For example, a flexible Polyofin (FPO) mem- brane can reasonably be expected to have a service life of more than 75 years, whereas a bitumen membrane of a similar thickness is expected to last approximately 25 years in service. Flexible materials such as PVC-P and FPO have superior crack bridging ability and stress crack resistance, when com- pared to HDPE.
Integral waterproofing
Offering buildability, repairability and reduced cost, integral waterproofing systems have gained in popularity. When relying on the concrete to provide a watertight barrier, the
the potential effect on the durability of the structure must be considered. Ongoing maintenance costs for sumps and pumps must also be taken into account, as well as any effect these extra design details have on the building’s design and useable space. These systems are well suited to refurbishment projects but
perhaps should be used as a backup in combination with a tanking or integral system for new build projects.
Go with the flow
To ensure buildings remain impenetrable to water, whilst meeting the building standards of today and the future, a measured and evaluative approach to the product selection needs to be taken. The NHBC, along with other insurers, has also upped the
ante having raised standards of waterproofing most notably in terms of habitable below ground accommodation, insisting that a combined approach to waterproofing should be used for Grade 3 environments. Careful consideration must be given to the selection of the
product, or products, as a single solution may not be right for the project. With below ground waterproofing, it is certainly not a case of ‘one size fits all’. In the light of this, an all-round solutions provider has the ability to to consider the entire waterproofing process to benefit clients.
Alex Burman is product manager at Sika Waterproofing enq.191
www.architectsdatafile.co.uk
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