240 Blackfriars | Allford Hall Monaghan Morris

A simple extruded parallelogram has been cut away in several planes: diagonally to the north, to orientate the building towards the river; at the base, to increase public space at street level; and across the roof, to create a dynamically-shaped sky room.

240 Blackfriars is a major development composed of two distinct components that seeks to define the skyline at a pivotal junction of road, rail and river. The site is initially sliced in two to create a large commercial parallelogram and a small residential trapezoid in plan. The parallelogram is extruded up 90 metres (20 storeys) to form a sharp-edged crystalline volume, which is then cut away to respond to context: to the south to minimise the impact to Ludgate House, diagonally to the north to orientate the building towards the river and city; at street level to add generosity to the public realm and across the roof to create a reflective triple-height ‘sky-floor’. In contrast, the dark masonry trapezoid is extruded up six levels and then carved away to create loggias, terraces and gardens for its ten residential apartments. Completed in April 2014, 240 Blackfriars provides over 220,000 square feet of high performance office space, animated by ground-level retail units.

Form
Inspired by the strength of natural geological forms, the basic 90m tall trapezoidal extrusion is cut four times to respond to both local and citywide context and to further enhance a strong structural internal geometry. In contrast, Cubitt House - the dark residential building - acts as a foil to the crystalline office building and emerges as a dark solid block developed as a punched masonry facade.

Realisation
Playing on the occurrence of mineral ‘forms within forms’ the structure of the core and frame are defined as basic concrete extrusions, with mutations where the pure geometry is cut. At the base this gives way to dramatic fair faced concrete raking columns and dynamic multi-faceted castings at the sharp perimeter corners. To the north and overhead facets, a steel frame creates greater clear spans, all springing from the star node at the critical junction of the façade and roof.

Capability
Providing 221,500 sqft of office accommodation over 19 storeys, there is flexibility to provide scope for either a single tenant or subdivision into a maximum for 38 smaller lettings with minimal internal columns. Individual floor plates vary between 11,000-12,000 sqft, reflecting the change in profile to the north, with a density of occupation at 1 person / 8m2 for lower levels 01-10, increasing to 1/7.5m2 for levels 11-19.

Responsibility
The building design has a design target of achieving an ‘Excellent’ rating under BREEAM New Construction 2011, and the BRE certified design stage assessment confirmed an additional 6% pass margin. Key enhancements include additional provision for cyclists and responsible sourcing of both materials and labour.