70 St Mary Axe

The CW system is specifically designed as unitised fully glazed in storey height modules.

Due to the building shape every single unit type, depending by storey location, is unique in height dimension and curvature, being vertically inclined at angles that vary from +14°, sloping outward at the ground, to -27° sloping inward at level 21.
The external projecting aluminium curved fins provide solar shading to the glazing from oblique sun angles whilst still providing excellent daylight penetration and occupant views out.

70 St Mary Axe

This solar shading is of particular benefit on the south (south west) elevation, significantly reducing overall solar heat gain and delaying (and thereby reducing) the peak solar gain load on this elevation, providing significant reductions in overall energy usage of the building cooling systems.

From level 21 to the top of the building, panels of curved aluminium (light blue anodised) mesh are positioned between the fins (light bronze anodised) continuing the blue line of the curved glazing below to provide visual continuity whilst maintaining the necessary degree of air permeability to the plant located at these levels.

Foggo Associates London
Foggo Associates London
Peter Foggo Associates was formed in 1989 by a multi-disciplinary team of architects, engineers and quantity surveyors, who had all successfully worked together for a number of years. The team was responsible for a number of distinguished and award winning projects (through the 1970s to 1990s) at Arup Associates, where Peter Foggo (1930 to 1993) was both a Partner and a Director. These projects were notable not only for their architectural quality but also for innovations such as pioneering use of the management contract at the Horizon factory, Nottingham and low energy office design at the Gateway Buildings, Basingstoke. The Finsbury Avenue and Broadgate developments in the City of London cemented the team's reputation for high quality commercial architecture built on time and to budget to fast track programmes. Competition wins for the Brno Technology Park in the Czech Republic and the masterplan and subsequent buildings at Leeds City Office Park enabled the practice to set new standards for low energy office design. The practice maintained and enhanced its reputation for contemporary rational commercial architecture in complex environments with projects in the City of London such as 111 Old Broad Street and 60 Queen Victoria Street. The practice's work completed to date ranges from small scale residential extensions (such as Sorrel House, RIBA Southern Region Prize 2002) to large scale urban mixed use masterplans and developments (such as Cannon Place, ICE Building of the Year 2011 and various other awards).
70 St Mary Axe

70 St Mary Axe

A distinctive elliptical form is changing London skyline: the “Can of Ham” is served.

Project Specs

  • Location: London
  • Year of completion: 2019
  • Contractor: Mace


  • PH: Sokari Higgwe


70 St Mary Axe

The cladding

In conceptual terms the external envelope of 70 St Mary Axe comprises two “façade” types: the vertical externally frameless, smooth glass east and west “gable” ends, and the elliptically curved sides and top rising from the base on the north running continuously in a smooth curve wrapping up and over the apex of the building and curving down the south side to the base on that side.

The clear differentiation between the two types of “façade” reinforces the visual definition of the building’s distinctive form.
Regular spaced rectangular metal vertical projecting fins with glass panels recessed between them, curved in profile to follow the building’s elliptical shape, form the typical north and south office cladding type.

North & South curved façades

The external fins are curved to follow and define the curved form of the building as is the whole façade including DGUs and unit frames.

The façades are sub-divided into 4 nr. twelve metre wide bays and 500m wide (approx.) solid panels, which follow the same external profile as the fins and are coincident with the perimeter structural columns.
From ground level to level 20, a high performance double glazed aluminium framed curtain wall unit system is carried on (or carries) the back of the fins, creating floor to floor vision areas and integrating bulkhead internal panels, which cover the depth of the floor construction.

Designed by

Foggo Associates London Architects

The development of 70 St. Mary Axe has created a stunning, semi-elliptical property, with c.28,000 sq m (300,000 sq ft) of net office space over 19 floors, arranged above a double-height foyer on the ground floor.

Sustainability is high on the agenda with the scheme providing a stunning geometry and also a highly efficient building BREEAM excellent.

The height and shape of the building have been developed to create a distinctive geometry in response to strategic local views. Vertical shading fins to the curved facades and glazed double wall cladding to the end elevations reduce solar heat gains to the office space. Other low energy measures, such as borehole thermal energy storage and energy piles, result in a design with very low carbon emissions. Although not one of the highest skyscrapers in the area, it has become a new landmark in the City of London.

Other Façade Systems

When viewed obliquely, then the metal surfaces predominate visually, such that externally these facades appear predominantly metallic, and contrast strongly with the smooth reflective glass appearance of the east and west gable facades.
The 12 metre spacing of the perimeter structural columns is expressed on the north and south facades with solid metal clad casings which also follow the curved profile of the building. At the ends these casings form the solid metal continuous perimeter edge to the east and west gable facades.

The orientation of the building, means it benefits from solar shading of the glazing by the fins for significant proportion of the day, thus reducing overall cooling load on the building services.

At the top of the building, perforated metal mesh is located between the fins in lieu of glazing, to allow free air circulation to the building services plant located at these levels, whilst also providing a semi - transparent screening of these plant areas from the street and adjacent buildings.

East and West - Flat façades

The east (south east) and west (north west) façades comprise high performance double glazed, externally frameless curtain walling units system to create flush, vertical homogenous glass elevations at the ends of the building.
On levels 2 to 20 the system comprises of floor to floor vision areas to the office areas with mullions generally at 1.5m centres (co-ordinating with the internal planning grid) and integrated back bulkhead panels, covering the depth of the floor construction. The system has been designed to be unitised in storey height, 1.5m wide modules.
Internal adjustable venetian blinds provide glare and privacy control. These blinds will ordinarily be in the lowered position with tilt control provided for office occupants and will only be raised for maintenance and cleaning purposes.

The venetian blinds combined with high performance solar control coatings to the double glazed units and the orientation of the building reduce solar heat gains through these elevations to the requisite levels for occupants comfort and overall building energy usage.

The units system has been engineered in order to reach the 1.3 W/msq°k u-value performance and an energy control of the solar factor for less than 34% with light transmission higher than 62%.
From level 21 to the top of the building, the glazed units are screened internally by a single glazed curtain wall system incorporated with an openable blind system (maintaining the appearance of the office venetian blinds), such that the top of the building appears contiguous with the cladding to the office areas on these elevations.