70 St Mary Axe

Ahead of the curve

Leading the construction of London's latest soaring skyscraper

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70 St Mary Axe Project summary


Nuveen Real Estate

Key partners

Foggo Associates, Arcadis, GVA Second London Wall

Services provided

Construct, Contracting


Corporate real estate, Commercial


UK - London and south-east England, UK and Europe

Project timeline

Start date
June 2015

Project story

A unique addition to the soaring skyscrapers of London's Square Mile, 70 St Mary Axe is both progressive in design and sustainability, while offering some of the most enviable views across the city.

Arranged over three basement levels and twenty-one floors above ground, 70 St Mary Axe is the latest edition to London’s increasingly visually-competitive skyline.

The distinctive, semi-elliptical form soars elegantly from the surrounding historic streets, and with its curved glass and anodised aluminium-finned elevation that wraps the structure, delivery required unique engineering solutions and a level of precision that pushed the boundaries of construction.

Never one to shy away from a challenge, Mace led the project as the main contractor from pre-construction to completion, taking learning from the delivery of The Shard, 240 Blackfriars and One Crown Place to maximise efficiency and quality throughout.

From column-free floor plates to curved cladding, to a core tolerance of just +/-12mm, the unique design of 70 St Mary Axe required us to think differently – challenging construction methods and implementing innovative solutions to achieve our client’s vision. 
24 storeys
28,000m2 premium office space

points of note

Column free floors

All the building’s floorplates are column-free. Cellular beams span the 12m from the concrete core to the faceted steel columns incorporated into the building’s curved facade. To give the building its curve, the raking columns were fitted with a curved, anodised aluminium skin to integrate it with the curved facade glazing. 


The core was built to a tolerance of just +/-12mm, due to the fact that the steel beams span off it, onto which the vertical steel frame is attached. The core had to be exact, because if it was off, the steel spanning beams would be out and the vertical steel structure would not anchor properly.

Prefabrication cost savings

In partnership with the design team we developed an innovative, cost-saving prefabrication solution for the mechanical, electrical and plumbing services and distribution systems. The prefabrication elements included plant room compartments, structural components, facade cladding and integrated core toilet finishes and services.

Reducing solar gain

To reduce solar gain, vertical shading fins were added to the curved facades and unitised double-glazed wall cladding enveloped the end elevations. Other low energy measures, such as borehole thermal energy storage and energy piles, resulted in a design with very low carbon emissions.

Preconstruction and utilities works

We managed all utilities disconnections and diversions during demolition. This included relocating two existing substations for the demolition phase and designing the planting scheme, as well as managing the cable diversions and coordinating the new electrical supply.


The basement is home to the plant that was too heavy to be installed in the roof-level plant room, such as the domestic water and sprinkler storage tanks, electrical distribution boards, and huge oil tanks to fuel the standby generators. The oil tanks were so large they had to be craned into position in basement level 2 before the level 3 slab was constructed above it.