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ExCel Phase 2, London, by Grimshaw

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East London’s ExCel exhibition centre is so big you can take a train from one end to the other - and Grimshaw has just made it even bigger, extruding it and injecting new life with a dynamic spiral form, writes Felix Mara. Photography by Edmund Sumner

You could take the Docklands Light Railway from one end of ExCeL London to the other; it’s that long. Or you could walk along the 600m-long boulevard that runs through this east London exhibition and conference centre. Either way, if you travelled eastwards, you’d soon run out of refreshing architectural experiences.

On a morphological level, and as a business model, ExCeL resembles a sausage machine. When I suggest this to Ben Heath, an associate at Grimshaw, architect of ExCeL Phase 2, he says that ‘the brief was to extrude this sausage’ to provide London’s principal international conference centre. ExCeL will be the capital’s second-largest Olympic venue and will host Ecobuild in March 2011.

Exhibition centres and conference centres, which are usually smaller than ExCeL, have a complex and sometimes distinguished history that can be traced back to the Middle Ages through the tradition of European trade fairs. One strand of this history is temporary buildings for world fairs; for example, the Crystal Palace, designed by Joseph Paxton for London’s Great Exhibition of 1851. Like ExCeL, the Crystal Palace had a central pedestrian route.

Another strand is permanent exhibition centres, such as the 1937 Earls Court Exhibition Centre, the 1976 National Exhibition Centre (NEC) in Solihull, and the 1985 Scottish Exhibition and Conference Centre (SECC). These need to be adaptable, with provision for expansion, subdivision, and access to overhead services.

The linear model used at ExCeL works well on sites that can accommodate axial extension. Alternatively, exhibition centres can be expanded by adding discrete or quasi-detached buildings, such as Foster + Partners’ Clyde Auditorium, added to the SECC in 1997. This expansion model is less likely to generate long, low proportions. Neven Sidor, Grimshaw’s partner in charge, notes that ExCeL is purely a commercial venture, in contrast to Grimshaw’s 2001 Frankfurt Messehalle, which is publicly owned and more focused on exhibition visitors and urban design. Sidor adds that, in the case of ExCeL, ‘the typology was already there’.

Phase 1, designed by Moxley Architects and completed in 2001, is enormously successful. The zones for its flat-floor exhibition halls divide neatly into rectangles of more than 4,000m², serviced by elevated lorryways on their external flanks, with all public access from the boulevard. This means that events and their set-up/get-out periods can run simultaneously. But Grimshaw was also aware of ExCeL’s flaws. Along with the poor lighting of the tedious boulevard, there was unsatisfactory pedestrian access from ground level, especially from the blighted Royal Victoria Dock to the south. Linear perimeter breakout zones had limited flexibility and the pedestrian route from Prince Regent Station was unsatisfactory. In the words of ExCeL’s former chief executive Jamie Buchan, ‘the building was designed around the exhibitors, not around its visitors’.

The spiral element is like a preternatural insect that has walked through the facade

Grimshaw has longstanding experience of capacious, flexible industrial buildings and sheds. I once asked a younger Nicholas Grimshaw, at a lecture illustrated by a parade of his large-span lightweight structures, whether he had designed any buildings that weren’t flexible. The simple answer was ‘No’. But Grimshaw’s analysis and architectural response, though receptive to ExCeL’s strengths, is also a critique. A practice that trades on the merits of flexibility must also understand its limitations, and this informed the design of the multi-purpose spiral element at the core of Phase 2. In section, this forms a gigantic coil with splayed ends, skewered by inclined columns, like a preternatural insect that has walked through the facade.

The spiral’s dynamic, articulated form provides a much-needed focus at the end of the boulevard and the approach from Prince Regent Station, turning approaching visitors through ninety degrees. It emerges from the facade, where it is a focus for views from London City Airport, and it acts as a circulation pivot, a bridging element, an entrance vestibule, a space for restaurants and a foyer for breakout spaces. It’s deftly planned, with a lithe, supple geometry made legible by the 20m-high surrounding spaces. A new hotel will block further eastwards extension of ExCeL and Phase 2 is an extrusion tweaked in several ways. Its continuation of the boulevard is top-lit by vast ETFE pillows, supported by masts and suspended steel ring beams.

ETFE costs less than glass and has a higher transmission factor that boosts daylight levels at the approach to the spiral. The perimeter breakout zones don’t continue into Phase 2. Instead, this space allocation is amalgamated in a large oblong hub that can accommodate bigger, wider layouts. The halls at the east end of Phase 2, which contain conferences and exhibitions, step down to ground-floor level, providing more height, external access at grade and more active facades, with the lorryway ramping down to ground level. This arrangement and the external staircase to ground level help integrate ExCeL with the dock. Moxley Architects’ steel outriggers that support the roof are omitted in Phase 2 because of flight-path restrictions and high-voltage power lines; inboard mast structures are used instead.

Heath emphasises that ExCeL Phase 2 ‘is a building designed by architects who take a great deal of delight in how buildings are put together. I like to think that it is very much a building in the Grimshaw tradition of innovative sheds, with a greater emphasis on internal spatial relationships and a more playful approach’. Grimshaw has a reputation for attending to the details of prefabricated elements and this has always had a playful aspect. The geometry of the spiral is beguiling, even tricky. It’s clad in radiused profiled metal sheeting, and the bright yellow finish to the recessed cladding gives the impression that it’s been sliced off. Heath compares it to the filling of a sponge cake.

Proprietary pavement lights were not available, so in-situ concrete and glass lenses are used to construct the ramp to the spiral. Post-tensioned reinforced-concrete slabs provide large spans and the architectural qualities of the spiral’s structure reflect on Grimshaw’s experience of collaborating with engineers. Faceted conference hall walls fragment sound reflection and form a range of volumes, with the required variation in acoustic absorption. The boulevard’s walls are concrete blocks with polished surfaces and false joints that conceal their module, so they look like square tiles.

The space around the spiral is flanked by a bespoke expanded metal anodised aluminium mesh, with inclined sections, so it looks more opaque from below. This is where Grimshaw has invested most in the detailed design. It’s cool, but it looks ephemeral and unfinished where used externally on the north elevation. Imaginative external lighting could bring it to life, but the budget is restricted: vertical strips of coloured polycarbonate cladding on the east elevation are not backlit and the exposed steelwork supporting the roof ‘s cantilevers has none of the refinement of the spiral’s steelwork.

‘It is very much a building in the Grimshaw tradition of innovative sheds.’

Grimshaw associate Ben Heath

Phase 2 improves circulation by diverting some passenger traffic to a new entrance, although it was not possible to provide direct access at station platform level because most visitors arrive on the north platform, separated from ExCeL by the westbound tracks. But the experience of traversing elevated platforms supported on stilts above the terrain below is part of the genius loci. On the level of urban design, ExCeL Phase 2 resolves the massing problem it addresses by engaging with the limitations of the commercial exhibition centre as a building type. It is inherently a behemoth. This is Docklands, not a typical European city-centre site calling for the touch of a sensitive urban designer. Grimshaw has embraced this challenge with boldness, conviction and invention.

Working Detail: ExCel Phase 2, London, by Grimshaw

“Spiral cladding”

Conceptually, the spiral is a continuous surface that extends the pedestrian route with accommodation in each fold. Materially, it is a surface with an inner and an outer layer: the metal-clad, ‘cold’ external face and the artificial-stone-clad, ‘warm’ internal face, with ‘cut’ edges that underline the geometry.

The external face comprises Kalzip TF 800 rainscreen cladding, polyester powder-coated in RAL 9006, with 400mm-radius edges forming a transition between metal-clad soffits, walls and roof. There are pressed aluminium fins, instead of Kalzip standard joint connections, on joint lines between panels and at interfaces with structural columns.

The internal face comprises fibre-cement rainscreen-cladding panels and reconstituted porcelain floor tiles. Fibre-cement panels and floor tiles were selected for the closest colour match, to give the impression that the internal surface is continuous. Both have a 400mm module to create a wrapping effect. The fibrecement face is fixed to top-hat cladding rails with stainless steel bolts. Slotted stainless steel trims at the base allow for cavity ventilation. The cladding has integrated, recessed strip lighting to underline the spiral’s geometry.

The edge of the spiral, where the surface is cut, has a vitreous enamel steel panel system. The yellow colour, RAL 1021, highlights the folding of the surface and gives an identity to the new east entrance. Vitreous enamel panels hook on to vertical U-channels with invisible fixings. T-shaped aluminium extrusion trims form the interface to adjoining cladding materials. Anodised aluminium extrusion trims are connected with tongue-and-groove joints, and curved trims are welded from flat elements. Base-clamped structural glazing balustrades have clip-on stainless steel handrails. The base clamps form upstands for external deck waterproofing.

  • Diarmuid Bradley, architect, Grimshaw

Specification Notes

Hard flooring to spiral Domus Ecotech DCO 03
Aluminium rainscreen cladding to spiral Kalzip TF 800
Toilet cubicles Thrislington Icon laminate doors and dividers
Vanity units DuPont Zodiaq quartz composite
Expanded metal mesh and supporting structure to conference box James & Taylor Eyetech natural silver anodised expanded metal mesh
Polycarbonate rainscreen cladding to south-east hall/auditorium Rodeca Bi-Color cavity panels
Roof insulation Kingspan Thermaroof TR26
Single-ply roofing Sarnafil
Curtain wall to front of spiral Schüco FW 60+SG, thermally broken
Curtain wall to conference box and clerestory Schüco FW 60+SG, thermally broken PPC
Curtain wall to spiral and car park entrances GEZE SL ISO
Conference box rooflights Duplus triple-skin polycarbonate domes
Aluminium rainscreen cladding to north and south halls Kalzip RS 45/400
Facing blockwork to boulevard Plasmor Vertiblock
Recessed strip lighting to spiral Selux M100 series continuous lighting
Luminaires to exhibition halls Thorn Concavia L 1x400W reflector luminaire
Lifts Schindler

Project Details

Start on site April 2008
Contract duration 24 months
Gross internal floor area 64,000m2 (excluding undercroft)
Form of contract Negotiated design and build bespoke contract
Total cost £152 million
Cost per m2 £2,350
Client ExCeL London
Architect Grimshaw
Project manager/cost consultant Gardiner & Theobald
Services engineer Hoare Lea
Main contractor/structural engineer Sir Robert McAlpine
Annual CO2 emissions Unknown

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