Waterproofing critical below ground structures
Many landmark buildings around the world including the Islamic Arts Museum, Doha; BBC Broadcasting House, London; and the London Olympics Aquatics Centre owe the performance of their below ground internal environment to this Grace innovation. Preprufe waterproofing is a unique and patented solution for waterproofing critical below ground structures. It is the choice of major international specifiers including Arup, Buro Happold, I M Pei, Foster + Partners and Zaha Hadid when protecting their most critical internal environments from the constant risk of penetration by water, gas or other ground contaminants.
The key success factor for the innovation of Preprufe is risk minimisation. Preprufe comprises a robust HDPE sheet coated with adhesive layers that combine to form an intimate bond with poured concrete. This seal not only prevents the ingress of water but also stops the water from tracking around the structure looking for a path to the inside. This problem is known as water migration and the risk can be effectively eliminated with this innovation.
Preprufe evolved from traditional methods of waterproofing that would use either self adhesive sheets, hot applied bituminous felts or similar materials. These methods would seal perfectly well to the substrate below the structure, but not to the structure itself. In addition these traditional materials would require a protective layer, further separating the waterproofing from the structure. Any water that managed to infiltrate to the wrong side of the waterproofing could easily travel anywhere around the structure, making it impossible to successfully trace the source of the leak. Ideally, the membrane would need to be installed upside down and without protection in order to properly waterproof the structure rather than the substrate. This was the concept that drove the innovation.
The technological breakthrough was a special acrylic surface coating developed by Grace. This coating allowed for the membrane to be installed with the adhesive face up allowing trafficking by following trades without the adhesive being damaged. The surface layer of Preprufe removes the tack of the pressure sensitive adhesive below, but is micro-porous and allowing the concrete in its liquid state to reach the adhesive. A watertight bond then develops which becomes permanent as the concrete sets. The bond does not rely on any chemical reaction, nor on special concrete or heat of hydration.
In addition to localising any leak at a microscopic level, the Preprufe membrane has simplified the installation process by removing multiple layers and complicated detailing. The protective layers of concrete or boards are eliminated reducing the depth of excavation, reducing the materials to be sourced and accelerating the critical path of the project programme which helped drive acceptance by contractors and clients.