Facade Type: Slide/Fold Panels | Architects: WilkinsonEyre | Location: London, United Kingdom
The impressive transformation of the Victorian triplet gasholder guide frames situated next to the Regent’s Canal at London’s King’s Cross is part of a larger urban redevelopment scheme, which is quickly gaining notoriety in London due to its great mixture of contemporary buildings and rich industrial heritage.
Client: King’s Cross Central Limited Partnership
Main Contractor: Carillion
Structural and Façade Engineer: Arup
M&E Consultant: Hoare Lea
Design engineering, fabrication and installation: Frener & Reifer
Facade execution period: September 2014 – March 2017
Folding/sliding units: approx. 355
Glass balustrades: approx. 1000
The historic guide frames
The triplet gasholder guide frames are grade II-listed and cast in iron. They were constructed in 1867 and are remnants of Pancras Gasworks, an 11 acres industrial development which opened to the south of the canal in 1824. Towards the end of the 20th century, the heavy industry moved to the outskirts of the city and only a few gasholders remained in service until 2001, when construction work started on the Channel Tunnel Rail Link. As part of the plan for the new development, the triplet guide frames were dismantled and sent to Yorkshire to be restored.
In 2002, architectural practice WilkinsonEyre won a design competition to transform the gasholders triplet into a residential scheme and by the start of 2016, the restored gasholder structures have been transported from Yorkshire back to London to be reassembled and re-erected on site.
The project developed by WilkinsonEyre Architects proposed three drums of accommodation, providing 145 apartments of studios, one, two, three and four-bedroom apartments to be housed within the elegant cast iron frames. Each building differs in height, designed to suggest a rise and fall in pressure inside the original telescopic gas drums.
The guide frames, including 123 columns, each one weighing between eight and 10 tonnes, have been restored by Shepley Engineers in Yorkshire. Despite being over 150 years old, the gasholder triplet was in remarkably good condition, largely preserved from decay by its 32 layers of historic paint. The restoration process involved removing the historic paint and manually inspecting every one of the 650+ components to identify stresses and repair them where necessary.
Prior to the guide frames’ reconstruction on site, Structural Engineer Arup has conducted an extensive study to prove that the gasholder triplet will not need either temporary or permanent external support from the new building’s structure, allowing it to stand proud on its own both during and after installation.
The three concrete-framed drum-shaped blocks are structurally independent and set back two metres away from the historic frames that encase them. To avoid impact on the re-erection of the restored gasholder frames, a unitised cladding system was developed so that cladding and balconies, assembled off-site, could be lifted into place and installed without external access.
The metallic adaptive building skin
The concept for the facade was to create an overall appearance that somehow still told the story of the gasholders. In order to retain the industrial aesthetic, a slide-and-fold skin of perforated metal shutters have been used. This creates a veil of shimmering metal which serves to unify the appearance of the façade behind the historic cast iron frames, adding a dynamic quality to the scheme.
The perforated metal facade rises upwards from the first floor and impresses with its motor-driven folding/sliding sun protection system which slides open at the touch of a button or iPad. Composed of perforated aluminium shutters manufactured by Frener Reifer, the metallic adaptive building skin expresses the architects’ concept of an animated, timeless building envelope.
The external look of the folding systems was adjusted to that of the rainscreen cladding, giving a variously perforated appearance to the entire facade.
The folding shutters consist of three types of 3mm aluminium panel units: fully perforated, half perforated and unperforated solid sheets. In addition to their decorative effect, the aluminium sheet perforations have the function of guiding daylight into the interior spaces. The bespoke pattern of circular holes is designed to allow approximately fifty per cent of daylight through to the windows and terraces behind.
The slide-and-fold perforated metal shutters
There are 355 integrated, up to 3.5m tall, completely openable, motor-driven folding/sliding units. The folding/sliding units can all be controlled individually and residents can place the folding units in a fully open or half-open position in order to enable optimum shading and allow the ideal amount of daylight to enter. In high winds a master control system is activated, via a trigger impulse from the weather station, causing the folding leaves to close automatically for their own protection. All three towers feature a wide variety of geometrically differing folding/sliding units. These are either single-leaf, double-leaf, quadruple-leaf units, or a combination of. A pair of leaves is always adjusted to the radius of the external faceting.
The colour of the sheets matches the grey framework of the gasholders and varies from one tower to the next, each gasholder cylinder gleaming with a different shade of metallic grey.
The dark steel cladding contrasts with elements of brass and bronze. Also, in order to produce an effect of depth, the suspended ceilings of the balconies were visually reinforced with a second colour.
The unitised interior facade
The full height unitised facade behind the spectacular folding shutters consists of aluminium profiles provided with both opaque and glazed elements. The up to 2.80m floor-to-ceiling thermally insulated triple glazing opens up the internal spaces towards Regent’s Canal and provides impressive panoramic views of London.
Almost all the 145 apartments have spacious private balconies or terraces with faceted glass balustrades. There are 35 different types of balconies, some cantilevered and some recessed, all of which serve as fixings for the outer facade. Most of the balconies are equipped with front-mounted folding/sliding units.
The intersection of the three Gasholder guide frames creates a large open inner courtyard. The three Gasholders are connected with each other at the ground floor of the courtyard through a glazed corridor, consisting of large-format glass sheets (width 2.2m / height 4m, with a single pane weighing approx. 1000kg).
Access from one building to the next is also allowed at the fifth and eighth levels of the courtyard through circular filigree walkways with approx. 1.30m tall curved glass balustrades.
All three roof terraces feature a large central glazed atrium roof comprising of steel and glass structures with capping profiles in aluminium. The three glazed atrium roofs have diameters of 9.6m, 14.5m and 17m and are equipped with large, automatically controlled ventilation leaves and smoke extraction apertures.
At Gasholders No. 10 and No. 11, the roofs are equipped with private terraces for the penthouse apartments. At Gasholder No. 10, access to the terrace is achieved via five small one or two storey glazed patios in the centre of which spiral staircases are located. The penthouses patios have SSG facades with integrated sliding elements and mirror-polished stainless steel panels and are used to direct daylight into the apartments as well as providing access to the roof.
Instead of the small glazed patios, Gasholder No. 11 features 25m² motor-driven openable sliding roofs, which both allow fresh air and natural light to enter the apartments and enable access to the terraces when in open position.
The lead facade constructor, Frener & Reifer, was required to design-engineer, fabricate and install several different types of facade and was also responsible with producing and testing prototypes.
The great variety of different items that had to be fabricated in small series was a challenge in terms of the design engineering, fabrication and installation of the building envelope. 2,000 individual drawings were necessary for the approx. 1,370 exterior facade elements and many parts of the external facade skin had to be installed by abseiling.
The design work, the production of prototypes, fabrication and installation were extremely demanding and involved short execution times. On occasions, this involved coordinating the collaborative work of up to 100 installers around the simultaneous installation of the cast iron structure by others.