AIG Headquarters, London
Consulting engineers: Mott Macdonald
AIG is the world’s leading international insurance and financial services organisation, the European headquarters were purpose-designed and built for them in the heart of London’s financial centre. A tight schedule and total waterproofing were the challenges facing the developers of the new headquarters. The underground structure had to be completely watertight as the basement was to be used for document storage. A totally dry environment fulfilling Grade 4 level of BS 8102 was required.
By providing an easy-to-use, membrane-free waterproofing system, PUDLO helped achieve all project goals, whilst significantly reducing contract costs and saving contractors over one month in construction time.
The original designs involved a membrane system but the subcontractors on the project, Duffy Construction, recommended an alternative waterproofing system. They recognised the benefits of using the membrane-free PUDLO system, an integral waterproofing additive that is specially formulated to protect against water ingress and aggressive chemicals and to withstand hydrostatic pressure. Having used PUDLO previously on other projects, the sub-contractors knew that the system was BBA approved, easy to use and can dramatically save construction time without compromising on watertightness. In fact one entire month was taken out of the construction programme by using the membrane-free system.
Waterproof concrete was used to create the 1.2-metre-thick base slab positioned 7 metres below ground level and this slab was placed on piled foundations. HDBR Waterbar was used on all construction joints to provide complete water resistance and excellent resistance to the passage of methane, carbon dioxide and radon. Had a membrane system been used there would have been the potential for leaks around each pile head, the PUDLO system eradicated this risk.
The PUDLO system also eliminated the problems that can arise with membrane systems around wall and slab joints and other overlapping areas.
Steven Brunswick, Technical Services Director at Mowlem recognised the advantages of using a concrete waterproofing additive. The additive reduces the water content and, as the concrete cures, the additive seals the potential water paths. He explained, “The concrete is in itself the waterproofing membrane and therefore the PUDLO system was the preferred choice for the AIG development.”
The development now consists of a 14-storey office block and a two-storey basement. The first underground level provides space for mechanical and electrical facilities and the second level provides space for document storage and car parking.