Travelling light

In creating a new Crossrail station at Paddington, Weston Williamson + Partners managed to achieve a high degree of openness, bringing natural light to platforms. As architect Rob Naybour explains to Sébastien Reed, this was not the only reason that this project is unusual in the infrastructure sector

Transport for London’s (TfL) latest mass transit project, and hailed as “Europe’s largest infrastructure project”, Crossrail has seen the excavation of nearly 120 kilometres of tunnel through London, linking west to east from Reading to Shenfield. The development has added 10 new stations across London, as well as numerous refurbishments inside and outside the capital. For the first time in UK major rail projects history, the entire set of designs for the new stations were developed concurrently out of a Crossrail office on Greenwich peninsula. With leading UK practices such as Atkins, Allies & Morrison, Foster + Partners, Grimshaw, and Hawkins Brown working on the line’s architecture, inter-practice collaboration was integral to the design process. The functional benefits of connecting the new Elizabeth line with international air travel, national mainline rail, and other London transport services made Paddington an attractive candidate for the Crossrail upgrade, despite the inevitable difficulties of creating a new station on the site. “The adjacency of Brunel’s Grade I listed 1854 station posed great challenges”, says founding partner Rob Naybour of project architects Weston Williamson + Partners (WW+P) – one of the UK’s most respected practices working in infrastructure. WW+P’s previous rail commissions include extensions to the Docklands Light Railway (DLR), London Bridge’s Jubilee line underground station, and various masterplans including for Paddington itself. This saw the practice working on the original station, providing a concourse adjacent to Paddington Basin, access to the Hammersmith & City line via a new underground station, plus enhanced taxi facilities. Gathering a wealth of contextual and practical knowledge of the original station and the surrounding area gave WW+P the edge when it came to competing for the leading design spot on integrating the new Crossrail connections. However, Naybour admits “it’s been a long journey” – his work on the station began some 12 years ago, upgrading links to the Hammersmith & City Line for TfL. The project’s scope (and commensurate workload for the architects) had expanded greatly since its inception: “What was really a very modest commission turned into speaking to various stakeholders, with key parties taking us on to develop a co-ordinated masterplan.” While Paddington Integrated developed the northern side of the station, Crossrail’s arrival would see the south side rejuvenated, as part of its brief of “a clear vision” for the rail hub.

An open layout

First glimpses of the new station are offered by a grand, 120 metre-long canopy constructed from 6.1 metre gridded glass elements. With the designers needing to respond sensitively to surrounding buildings, the planar structure was designed to sit apart from the neighbouring, listed Macmillan House. The station itself is housed within an immense box measuring 264 metres long, 24 metres wide, and 21 metres deep, positioned parallel to and in between the adjacent Macmillan House and Eastbourne Terrace. A 90 metre-long gap in the station’s roof slab, spanned by the canopy, houses two banks of escalators at either end and a pair of glass lifts in the centre. “Normally in these stations, lifts are tucked away round the back, which makes this slightly unusual,” remarks Naybour. Both escalators and elevators descend approximately 11 metres to the station concourse. With nothing but four horizontal supporting props bracing the diaphragm walls and the glass canopy 20 metres overhead, the concourse is open and airy, providing a strong sense of arrival both to pedestrians ascending from platform level and to those descending to catch their train. Four further banks of escalators (as well as the lifts) descend the remaining 10 metres to the platform level. Five vertical elliptical columns topped with widening capitals are staggered at 18.33 metre intervals across the station’s length, bearing the combined load of the concourse slab, roof slab, and the canopy. The architects worked hard to spread these columns as far apart as possible to maximise openness. At either end of the station are two large plant modules, extending the entire height of the station. Fitted with intermediate slabs between concourse and ground level for increased floor area, the plant areas also accommodate sets of staircases, back-of house facilities and tunnel ventilation plants which can pump 200-300 litres of air per second through Crossrail’s tunnels. Overground, the plant areas are flagged by two large box enclosures made of precast glass-reinforced concrete.

Collaborative design

Despite admitting it “sounds rather mundane,” Naybour says the ‘common components package’ arrived at by Grimshaw and Atkins was key to the design of most of the stations, encompassing the look and feel that runs across the whole of Crossrail. It included functional and aesthetic features such as the wayfinding and signage, technical components including safety doors on platforms separating passengers from trains, advertising strategy, and seating. It was recognised fairly early on in the project that Paddington stood alone among the other stations being designed for Crossrail. The others were being excavated underneath buildings, while Paddington consisted of a big open-cut box next to a Grade I listed building. According to Naybour, WW+P were on one hand liberated by the model they were working off, but on the other, subservient to Brunel’s historic station next door. Stakeholder collaboration was a constant feature; WW+P conducted meetings with Heritage England and head of strategic planning at the Borough of Westminster Graham King every three weeks, bringing a transparency to the design process which proved fruitful. “Whenever we were making lots of design decisions, we would present our thoughts and where we were going – that was incredibly useful,” says Naybour, “it provides a focus for both the client and the team.” Crossrail’s ‘modulation’ – which describes the scale of standardised panel sizes across a project – was consistently applied at 1500 mm, but Paddington was the exception: “The principles were the same, but we were aligning with a listed building. Brunel’s station was set up on a rigorous 10 ft module, so we adopted that.” As well as looking to the surrounding area for inspiration, the designers took an open-minded approach to embracing the visual qualities of the structural engineering at Paddington. The vertical columns were intended as temporary solutions, but in conversation with the design team it was decided that their appearance as well as the cost saving supported the solution of retaining them. Says Naybour: “I think it’s very important for architects to take an interdisciplinary approach with these buildings,” he continues, “you’re working with the engineering, but you’re also pushing it.” The integration of interior lighting was one important feature distinguishing the station from its siblings across the Elizabeth line. Picking up on the 10 ft grid, large “inverted mushroom” or “lily pad” shaped light fixtures with an anodised finish are nestled into the circular recesses seemingly scooped from the coffered roof slabs. As well as maintaining a common rhythm across the entire station, these devices mitigate glare and enhance the station’s visual identity. Like the station itself, the structural slabs were built in top-down fashion, being laid on the ground with a metre and a half of concrete poured on top of them and their steel reinforcements. Then – in a move which required archeological precision that was a challenge with a JCB – earth was carefully excavated, chiselled away from beneath to reveal the finished slab. “The concreting work is of a very high quality,” assures Naybour. Over 100 light brown brick panels, some weighing more than 10 tonnes, clad the inner walls of the ticketing hall as a continuation of the original Macmillan Terrace facades. Anodised bronze panels clad the station’s supporting columns and the walls of the hall, forming part of the “restrained and earthy” colour palette: “These buildings are around for a long time and one of the key issues is that they are not heavily maintained – mainly due to limited access – so robustness is very important,” comments Naybour.

Naturalised light

Before WW+P began work on Paddington, the existing site had become, in Naybour’s words, “a taxi hell”. Therefore, a significant move within the Paddington Integrated project the firm also designed was relocating taxi access from Eastbourne Terrace to the northern side of the station. It was this re-arrangement that afforded the architects the space to implement the cut-and-cover box model, and in turn to create something unique for the public. The underground space that Paddington has is unusual, because it’s connected to the street, says Naybour – “a sort of implied public realm.” It consists of three levels: Departures Road, directly in front of Macmillan House; the concourse, 11 metres below; and the other side of the gap, Eastbourne Terrace 3.5 metres higher than Departures Road. From Departures Road and Eastbourne Terrace, pedestrians can peer over into the concourse below. The advantage of this configuration is that passengers are kept above ground for as long as possible. While the canopy provides shelter from the elements, its transparency facilitates, in Naybour’s words: “A visceral connection with the outside world,” further intensified by a sprawling, nature-inspired artwork overhead. The design team set “quite an open brief” for artists to provide works for the spaces. Three were interviewed, and the decision to commission Spencer Finch was “almost unanimous”. Picking up on the practice of cloud categorisation, Finch’s dynamic artwork – Cloud Index – depicts a cloudscape, printed across the glass canopy itself. As a result, daylight casts shadows over the public realm beneath which change over the course of the day. “Sometimes there’ll be clouds on top of clouds, sometimes the sun will shine through, casting shadows, sometimes you’ll see buildings through clouds, and at night, of course, it’ll look completely different,” says Naybour. Due to the nature of the artwork, the canopy had to be painstakingly pieced together like a jigsaw, lifting the 220 prefabricated glass panels, each weighing over a tonne, into their respective places using cranes and suction cups. In addition to enhancing passenger experience, the considerable amounts of natural light entering the station reduces energy use. Compared to the embodied energy expended during the station’s construction, the amount required to run it “is really tiny,” says Naybour. Crossrail worked directly with the BRE to put together its own energy standard, which is reflected in the use of LEDs and recyclable waste storage.

Security

Despite the overarching design driver being openness, safety and security were also a crucial factor in what is a busy London location, particularly in the canopy design. Strict blast-proofing requirements were imposed on top of the structural criteria, demanding complex engineering and even testing with explosives. To gauge precisely how the structure would react in the event of an explosion, a replica bay was constructed and taken to Cumbria to be tested using actual detonations. In further security-conscious interventions to the external public realm, purpose-built benches and bollards have been included to blend in with the visual language of the canopy’s cigar-shaped steel columns. Positioned around the void, they block the trajectory of cars or buses potentially leaving the Eastbourne Terrace roadway, or delivery vehicles in Departures Road. Naybour notes: “You’re trying to deal with these big technical issues, but in an elegant way that doesn’t look heavy handed.”

Commitment to concept

The sheer scale and abundance of variables that must be considered in such high-use and long-life civic projects as Paddington’s Crossrail station is bewildering. They combine heritage, conservation, transport integration, way-finding, servicing and security – few other typologies are so intensive in what they demand from he architect. However the rare opportunity to design for such a choice plot in London was matched by WW+P’s distinctive design concept for the station, as Naybour summarises: “We’ve created a building that you can walk past at 3 o’clock in the morning and look straight down into an underground station. It’s unusual.” The station was due to be open in December, but this was recently put back to autumn 2019, following Crossrail’s announcement it needed more time to complete further “infrastructure and extensive testing” across the central section of the Elizabeth Line. The new building will then assume its critical daily role as a link in the Crossrail chain, helping to transport some 200 million passengers each year. Perhaps chief among the design achievements of this complex scheme was providing an underground station with such a highly unusual degree of openness. Despite all of the plusses, Naybour coyly admits to frequent questioning during the project over what would happen if people threw rubbish down into the station from above. His straightforward response: “Well, you have to go and pick it up.” It’s impossible to solve everything with design, but WW+P’s attempt to bring the underground closer to the surface has delivered a unique transport hub sure to make Londoners proud.