Argent’s latest addition to its huge King’s Cross regeneration has turned industrial heritage into high-spec homes. Arup’s Ed Shearer explains how it was done.
Contemporary urbanism married with stunning Victorian industrial heritage is a description that comes to mind when reflecting on the engineering designs for Gasholders London.
The grittiness and sheer ambition of Victorian engineers has been embraced by adopting modern 21st century analysis and digital tools, underpinned by clever structural engineering.
Gasholders Kings Cross Arup Argent 2
Rising above the canal docks and Victorian warehouses north of King’s Cross, these iconic gasholder guide frames stand have been restored on the north bank of Regent’s Canal. Three of these frames are at the heart of a new residential offering from Argent called the Gasholders, which reached completion earlier this year.
Arup has worked closely with developer Argent on its vision to regenerate the former industrial site north of King’s Cross since the partnership took ownership of the land in 2000. From early feasibility studies informing the masterplan, through to delivery of many of the buildings, Arup has provided integrated multidisciplinary advice throughout the complex development.
Retention of the rich industrial heritage at King’s Cross is central to Argent’s redevelopment. The repurposing of the gasworks infrastructure, so quintessential to the area, is a thrilling starting point for much of the new public and private space.
The engineering challenge
The Gasholders project presented unique engineering challenges, both in the restoration of the Victorian gasholder guide frames, and in the design of the new residential blocks in collaboration with architect Wilkinson Eyre.
The Grade II-listed guide frames were built in 1879 to house new, enlarged storage bells for gasholders 10, 11 and 12, which remained in active use until 2001 when they were dismantled to make way for St Pancras International.
Gasholders Kings Cross Arup Argent 3
The frames, comprising cast iron columns and wrought iron lattice beams, were stored temporarily at the east edge of what was once the gasworks site. A series of studies by specialists at Arup defined a strategy for restoring and repairing the guide frames such that they could safely be reassembled and remain a striking feature of the landscape.
A new location on the north bank of Regent’s Canal was identified for the frames and, in a competition announced by Argent, Wilkinson Eyre won the commission to design a residential offering based on its concept of three cylindrical blocks set within the guide frames.
With a strategy for their reuse in place, the frames were relocated to Barnsley for refurbishment by Shepley Engineering and structural engineer, Craddy, and design of the new residential blocks began. Arup provided consulting advice on structural, civil, geotechnical, façade and wind, while Hoare Lea led on building services.
The geometry of the guide frames posed a significant constraint on design of the new buildings, and successful delivery of high-spec residential units within these required careful integration of design goals from the start. Early design decisions were crucial.
Gasholders Kings Cross Arup Argent 3D frame
Detailed early studies of the floorplates justified ambitious minimum structural depths, set storey heights, and enabled early apprehension of an efficient yet flexible structural diagram. These allowed Wilkinson Eyre to proceed with extensive massing studies to achieve the right unit mix.
The result was three lean concrete frames, optimised for maximum internal space, on a grid accommodating a large variety of non-stacking apartment layouts and basement parking, without resorting to transfer structures.
Non-linear analyses of the slabs justified efficient and simple reinforcement detailing for ease of construction. A unitised cladding system was developed whereby cladding and balconies, assembled offsite, could be lifted into place and installed without external access, with minimal impact on the re-erection of the restored gasholder frames 2 m from the building envelope.
Within the three circular blocks, a fourth extruded circle provides a central courtyard where the intersection of the three Victorian gasholder frames is revealed. Floating at the top of the courtyard, circular steel bridges provide graceful links between the three residential blocks.
Gasholders Kings Cross Arup Argent Bridge Diagram
Making use of the geometric stability of a closed ring, the bridge decks are supported from the buildings on single row of diagonal props without the need for horizontal tie-back elements. This pared-down structural diagram not only provides a sense of lightness, but also releases restraint forces generated by thermal movements in the decks and sway in connecting buildings.
The slender steel bridges contrast contemporary structural design with the Victorian ironwork of the gasholder frames. This integration of new and historic design is replicated across the wider King’s Cross Central development. From brick and iron to concrete and steel, the regeneration of the area is rich in its theme and variations.
Gasholders Kings Cross Arup Argent Central Courtyard
Argent’s commitment to preserving engineering heritage at King’s Cross has provided the opportunity to blend contemporary architecture with Victorian infrastructure, and to integrate state-of-the-art engineering with its industrial history.
Gasholders London was unique and rewarding project borne out of intense collaboration between developer, architect, engineer and contractor. For us, it’s a joy to behold.
Ed Shearer is structural engineer at Arup