King’s Cross Square

If ever a site presented challenging constraints it’s King’s Cross Square, Stanton Williams’ new public space outside London’s King’s Cross station. When passengers pour out of the station into the 7,000m2 square, little do they know they are walking just 300mm above the roof of the London Underground ticket hall. But proximity to this and other underground infrastructure, such as the Fleet Sewer, had a major impact on the firm’s design of the new space, influencing drainage strategy and trees in particular. 

Constraints weren’t just subterranean; prominent London Underground ventilation shafts within the square and perimeter security bollards also challenged the creation of a unified hole. And while this needed to be a civic space worthy of the splendour of the newly-refurbished Lewis Cubitt station, it was important that it did not compete with the terminus.

Stanton Williams worked with these constraints to create what it conceived as a ‘welcome mat’, edged on three sides by an apron of York stone, for passengers leaving the terminus. 

The design, won in open competition in 2009, uses two types of granite to create 1200mm wide parallel bands that reference the terminating train lines within the station. Seating, trees, and raised planters are set on an axis within these stripes, which run perpendicular to the facade. This rigour imposes an order on the wedge-shaped site that is strong enough to deal with the three protruding ventilation shafts. Rather than remaining disruptive elements, these are instead absorbed into the square design by being treated as craters growing out of the landscape, according to Stanton Williams associate Stephen Hadley.

Robust, easy to clean granite was specified in two shades – a darker Crystal Black Chinese stone and a lighter SPI granite from the Granitos Pardais quarry in Portugal, both with a flamed finish chosen for slip-resistance and aesthethic quality. Where the bands terminate near the facade, the square continues in the lighter shade of granite – except for the eastern corner, which is paved in the darker shade. Granite also appealed to the architect because of its success as a cladding material, since a key aspect of the square is the continuation of the paving to form the cladding of the seating/planters and vents.

All three vents – a rotunda to the centre rear of the square, an egg-shape to the west and a small rectangular push vent east of the facade – are clad in the darker granite. In addition, two larger, curved vents have been expanded to incorporate kiosks and information screens. 

This base skirting detail on the curved vents was particularly challenging, incorporating both the curve of the vent in plan, and its curve rising out of the paving. Rather than being facetted, the curved granite was cut to order in China and assembled on site around the vent. The result is practical as well as visually pleasing – providing an easy to clean intersection between paving and cladding.

The granite vent cladding also incorporates vertical ventilation slots set at a 3m high datum. These impose outward consistency on the more random ventilation grilles within and contribute to the architect’s idea of giving the vents a plinth, fluted middle and canopy. Downlighting in the top of the vents highlights the vertical details, while the Rotunda’s illuminated parapet gives a halo effect. The darker granite continues beyond the Rotunda towards Euston Road.

‘We wanted to take something very utilitarian and unloved and turn it into something quite sculptural,’ says Hadley.

Set outside the striped bands, the egg vent is used to help signpost the station’s main entrance towards the west side of King’s Cross; the proximity of platforms to the facade means the front of the building is used only as an exit. 

Seating at the east along Euston Road is formed from granite-clad concrete bases supported on a steel frame, and incorporates concealed, below-seat LED lighting. On the west are two stretches of benches/planters. Planters rise to around 1100mm between seating on either side, and can themselves double as higher level seating. Like the vents, the idea is that these benches are emerging from the landscape.
Four smaller benches sit at the head of the striped bands in front of the facade, each facing a monolithic information panel, which also discreetly includes cctv. 

Drainage was one of the biggest challenges across the square, which has a 500-600mm fall. Visually, Stanton Williams wanted it to be as flat as possible to avoid distortions to the strict geometry of the paving. Yet it also had to be designed to ensure the surface gradient fell away from entrance thresholds to avoid potential flooding of the mainline or underground stations, or run-off to the public highway. There were also limitations on outlet positions caused by the proximity of the station hall roof. 

Arup Infrastructure used a three dimensional surface model to analyse the shape of the surface and the flow direction of rainwater run-off, and simulate a variety of storm conditions to determine what drainage capacity was needed. This resulted in some areas being lowered by up to 400mm and others raised by up to 300mm.
‘Too shallow gradients could result in ponding and too steep gradients could visually impact the dark and light granite stripes,’ says Arup Infrastructure associate director Craig Rew. ‘A series of subtle ridges and troughs were introduced in the paving in order to influence the flow direction of rainwater runoff.’

Gulleys were rejected as they’d increase the number and variation of gradients across the square and might be a hazard for high heels. A more discreet approach was essential. The solution was twofold. A linear drainage channel was introduced to the perimeter of the square to intercept run-off heading for the public highway, using Aco’s MultiDrain with Heelsafe stainless steel grate. In addition, unobtrusive twin-slot drains with stainless steel grilles – Aco’s MultiDrain with Twin Offset Brickslot – were used within the square itself, including one drain parallel with the main facade. Water is then channelled into a network of new sub-surface pipes and chambers that discharge into the Fleet Sewer via three new sewer outfall connections and two existing connections. 

The trees issue highlighted the architect’s tricky balancing act between client Network Rail, London Underground, English Heritage and local community groups.

Community consultation revealed a desire for more greenery in the square as well as the 12 Sophora Japonica trees proposed for the planters on the west, which are expected to grow to the same height as the nearby egg shaft. But the architect wanted to maintain as uncluttered an environment as possible and there was concern from English Heritage that mature trees would in time obscure the newly revealed canopy-free station facade. The solution was to incorporate five more – German plane – trees over to the east of the square at the front of each run of bench seating. Root space was sufficient to dispense with raised planters. 

Since King’s Cross is equivalent to airports for security risk, security-approved bollards with deep foundations had to be used at 1200mm intervals around the perimeter to prevent vehicles getting through. To the east, the positioning of the benches deliberately breaks up this line, with bollards interspersed in pairs between the seating. This is itself constructed with concrete bases built to security specialist engineering requirements. 

For the lighting, the architects worked with Studio Fractal to design three 18.5m high bespoke masts. These address the height of the facade, and are broadly in line with the side and central towers, while six smaller masts define the edges of the square next to the Egg ventilation shaft and tree planters. Stainless steel columns are combined with iGuzzini LED lighting, with a shot-peened texture specified to give a robust finish on the masts up to a 3m level, and a brushed steel finish above. 

The overall effect may seem to some a little austere, although this will be softened as the trees grow. But for Stanton Williams it was important that the square be a backdrop to the fine station exterior rather than seek to be the main event, providing a restrained setting ripe for animation by the 140,000 daily arriving passengers and passing pedestrians. 

Client Network Rail
Architect Stanton Williams
Multidisciplinary engineer Arup
On site engineer Robert West
Lighting design Studio Fractal
Arboricultural consultant BHSLA
Contractor J Murphy & Sons
Station architect John McAslan+Partners

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SUPPLIERS
Yorkstone Johnsons Wellfield Quarries [Szerelmey] • Granite Hardscape [Szerelmey] • Lighting masts iGuzzini / ProStainless • Metalwork McGrath and Lee Warren • Glazing Wrightstyle and Windell • Glazed doors Ingersoll Rand • Drainage channels Aco • Roofing Sarnafil • Rendered soffit Marmorit • Grilles Neaco • Bollards ATG Access • Louvres Levolux • Landscaping Willerbys • Manholes Jones of Oswestry • Gates to Tube Mercian • Roller shutters LBS • Signage Browse Bion • Lighting and comms Fourways • Sealant to paving Community Clean • Metal ceilings SAS
Lighting Bega, ACDC Lighting / Kemps Lighting