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240 Blackfriars

AHMM designed a trapezoid shaped, complex building in order to turn an awkward site to the client’s advantage. Aesthetically this mixed-use site just to the south of Blackfriars Bridge suits its central location and provides the surrounding area with a striking new focal point.

The tower’s unusual shape, in combination with height restrictions governed by planning and civil constraints, raised a number of complex issues for our team to solve.

The concept of the internal design was simple, incorporating office and residential units with retail spanning across the lower floors. There is also an adjoining structure containing 9,000 ft² of residential in ten apartments. This proved more challenging than the tower itself.

In terms of substructure, the building, including concrete box basement, is adjacent to a railway viaduct: potential vibration issues for both parties will require ongoing assessment of ground movements. The brown-field site also presents a number of concealed obstructions including slabs and existing services. Demolition removed some of these, but piled foundations, sleeved to prevent collapse due to the soil’s high water table, have been meticulously designed around the remainder.

Above ground, the off-centre, asymmetrical design of the building caused various complications. An eccentric core introduced torsion and a potential lean towards the west; sophisticated analysis was used to predict the movement of the core and we proposed to orientate the core in the opposite direction in order to balance the forces.

Due to its height, concrete was chosen as the most appropriate material for the frame. Visual concrete is particularly important, especially the double height ground floor columns, constructed through a testbed process. Since the structure widens above the base, we designed a second floor transfer slab reinforced with steel elements and post tensioned tendons to direct horizontal loads back to the core.

A triple height glazed space below the roof will provide spectacular views of the Thames; this was created by two triangular steel frames that required minimal columns, and a large truss at the roof’s edge.

Trapezoidal shaped mixed-use development on a very constrained site

LOCATION
London, UK
CLIENT
Great Portland Estates
ARCHITECT
Allford Hall Monaghan Morris
PROJECT VALUE
£ 80 million
COMPLETION
2014
AWARDS
  • 2015 NLA Award – Winner of Office Interior Design