Cannon Street by DelvenDahl Martin arChiteCtSPhotography by Tim Crocker

30 Cannon Street is a Grade II listed office building that occupies a prominent wedge-shaped site near St Paul’s Cathedral in the City of London, and was designed in 1977 for the London headquarters of Crédit Lyonnais by Whinney Son & Austen Hall. The building was the first construction in the UK to use glass reinforced concrete (GRC) panels (developed by Pilkington and Arup) on its façade. In 2015, 30 Cannon Street was added to the National Heritage List in recognition of its architectural value and contribution to the built environment.

In 2013 Delvendahl Martin carried out a feasibility study; our brief was to determine the re-development potential of the building, in response to current market conditions. We were subsequently appointed to undertake a comprehensive refurbishment that included the reconstruction of the 5th floor to incorporate additional space, the refurbishment of the entrance lobby and a new roof terrace. In addition, we carried out the upgrade and re-location of the existing building services and the re-glazing of all the main façades. Our aim was to preserve the architectural integrity of the building, which required extensive research to identify the original elements, modifications and later additions. This research helped to establish three main design principles that our new elements adhered to: geometry, materiality and colour.director, Achitect

Site plan

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Ground floor plan Ground floor plan

5th floor plan 5th floor plan

0 5m

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Specification statement

As with any refurbishment project, most of the decisions regarding the selection of products were made to achieve a balance between the existing and the new elements. In this case since the building is listed, attention had to be paid to make sure the integrity of the original design was not only maintained but enhanced. This was articulated by establishing a clear set of principles from the outset, where new components not only had to match the quality and robustness of the existing, but also either follow the colour palette or the geometrical principles of the building. The main objective was to create a continuity of the spatial sensibility whilst avoiding

pastiche. This approach becomes clear for instance in the design and rhythm of the new curtain wall façade which is based on the 1.5m structural grid. The white vertical fins have the same slope as the GRC, which makes the facade read from certain angles, as a seamless continuation of the existing. Another example is the geometry of the new roof garden planter and bench that was generated from a delineation of the building’s footprint with its characteristic rounded corners. Short timber slats were chosen as the main material for their flexibility to follow different radii and absorb tolerances. Eric Martin, Director

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Project data

Start on site March 2015vCompletion September 2016 Gross internal floor area 2500 m2 Form of contract Bespoke contractConstruction cost per m2 £5 millionArchitect Delvendahl Martin ArchitectsClient Romulus ConstructionStructural engineer ArupM&E consultant Hoare LeaQuantity surveyor & cost consultant AECOM Glazing consultant NET Project Management ConsultancyLandscape architect (roof terrace) Applied Landscape Design and Willerby Landscapes Ltd Lighting Supplier for the Lobby: The Light LabProject manager Romulus Construction CDM Coordinator Bernard Williams AssociatesApproved building inspector HCDMain contracto CapelCAD software used Vectorworks and AutoCad

Section A–A 0 2m

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Curtin wall façade detail

GRC façade detail

Glazing door detail

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