Weight saving structural concrete for hotel rooftop extension

The challenge was to construct a roof top extension on top of the luxury hotel NOBU in Shoreditch. The plan was to add an additional 1 storey of hotel rooms, suites, dining areas and open terraces that would replace the existing planted roof.

The chosen solution was Tarmac Toplight C lightweight structural concrete in a pump mix with the addition of steel fibres, ensuring maximum weight loss of 35% with no compromise on structural concrete performance.

By adding steel fibres into the lightweight mix the composite metal deck system could be installed without the need for traditional expensive and slow steel reinforcement across the deck. The use of lightweight concrete, furthermore, reduced the load by 35% which meant the existing structure did not need to be reinforced or under pinned. The construction programme time was also reduced considerably.