Low lights are the highlight at DSDHA’s Exchange Square, London

It often seems a little misty first thing in the morning in Exchange Square, the newly redesigned public space around the back of London’s Liverpool Street station. This is no quirky microclimate, just one of the atmospheric little touches – courtesy of concealed water jets – in this poetic piece of public realm design by DSDHA. At the other end of the day, meanwhile, the square’s curvaceous contours and cascading water feature are accentuated by elegantly-concealed lighting as part of an after-dark lighting scheme designed by Speirs Major.

According to Speirs Major associate partner Benz Roos, the lighting scheme focused on enhancing the many sensory aspects of the square’s design, including the textures and colours of the planting and the movement of wind and water. 

‘By playing up these elements, we aimed to encourage people to slow down, take note of their beautiful surroundings, and enjoy a moment of serenity in the city,’ he says.

The 6,000m² project is part of a broader public realm strategy by DSDHA for British Land’s Broadgate estate, to encourage more use after office hours and at weekends. Although conceived long before the pandemic, the strategy chimes with new workplace priorities, such as a particular emphasis on wellbeing, by providing a better external environment for workers on the estate and, it is hoped, for an increasing number of visitors.

While the other key public spaces were given relatively light-touch, quick fixes, Exchange Square needed deeper surgery, resulting in a £16 million investment to transform this problematic space into somewhere that people would want to spend time. Positioned on a raft over the tracks between the station and Exchange House, the square was largely hard landscape, except for a small patch of grass that needed replanting several times each year. Its dominant feature was a large water feature to the east. A 3m drop across the site had led to multiple level changes and access issues, with a messy accretion of steps and rails. Signage was poor, and lighting harshly bright.

DSDHA’s new landscape is a radical and welcome change, creating an altogether different, more intimate, sociable atmosphere that ‘nurtures plants and people’ according to the practice. 

The square has been re-levelled to create two principal levels rather than the five it replaced – a complex logistical task given the location – and the big water feature removed. At the rear, the level has been brought up to create a larger flat area on the same level as the undercroft of Exchange House, suitable for temporary events. Clad in French limestone, this overlooks a terrazzo amphitheatre at the station end, with a ramp providing step-free access alongside the amphitheatre down to the bottom – the second main level. 

The most eye-catching element is a meandering ridge that flows across the square in a continuous ribbon. This is inspired says DSDHA, by the salt marshes of East Anglia – the region served by the adjacent station. The line is a deliberate device to counter the movement of people through the square by providing a new landscape to dwell. Imagined as a rounded platform edge, this is faced in weathering steel, and is supplemented by a timber boardwalk following the same line, with additional sinuous seating. The ridge – which doubles as seating – continues on and upwards to define the roof of a retail unit alongside the amphitheatre. Amphitheatre seating is provided in bespoke patterned terrazzo (also used for the planters), cut through with a multi-level cascade of water forming shallow 30mm deep pools. Lush planting is positioned to the top and sides of the square in areas where the loads could be supported by the existing floor slab. These also relate to the movement of pedestrians, with the densest planting and lawn area close to the route from the Sun Street passage down the side of the station.

Speirs Major’s nuanced, integrated lighting accentuates the square’s distinctive new topography. This was, says DSDHA director Tom Greenall, very much a collaboration, with architect and lighting designer aligned in a shared aspiration for low level lighting both in terms of lux and height to create a more intimate environment. Other priorities included highlighting the planting.

Roos says that the lighting design was a juggle between security considerations and the desire to create a more intimate, sociable ambience for those in the square. Another factor was the appearance of the lighting from above when viewed from the overlooking offices. 

With the surrounding buildings already providing so much lighting of their own, the emphasis was on bringing light levels down in the square and then highlighting a few choice design elements including the water features, seating contours, and the planting. This is mostly done at a low height, with a few key exceptions. Lighting columns are kept to the east and west perimeters, including the main thoroughfare through the square from Sun Street, with WE-EF post-top and wall-mounted luminaires providing sufficient light for security purposes. Low-level bollard lights by DW Windsor aid way-finding by marking primary paths through the landscape. These also graze lights over the planting.

To create an intimate atmosphere with no jarring light sources, lighting was integrated beneath the continuous ridge, and within slatted timber benches and amphitheatre terrazzo seating, giving soft, indirect light. In the case of the cascade, this treatment illuminates the rippling surface of the water. These details required extensive collaboration between DSDHA and Speirs Major, with the lighting designer offering suggestions and sketch details for how lighting could be integrated, and as the design evolved, the architect developing the niches and nooks, says Greenall.

Large mock-ups were commissioned of both the steel ridgeline and the water feature to trial different treatments and ensure the light was sufficiently concealed in the niches while still providing enough of a wash of light. This investment proved invaluable in delivering the final design, with details amended accordingly. The final version of the terrazzo seating has lighting slots in openings two-fifths the height of the total step height. Inside the slots, a concealed niche houses the LED strips.

Architape LED strip lighting was specified and integrated into the steel ridgeline, terrazzo seating and cascade, and benches accordingly. iGuzzini floor washers are used for the steps on the pathways where there are no handrails.

The mature silver birch trees in the new planting are accentuated with lighting positioned in the foliage with minimally visible cables. Uplighters strapped carefully to branches highlight the silver bark and delicate leaves, while downlighters create dappled lighting effects through the foliage and onto the ground level planting to enhance the atmosphere of the square. These are supplied by Stoane Lighting, with one uplighter and two downlighters in each tree. The colour of the light is adjusted tonally with each season – in autumn, warmer white light complements the autumn leaves and bare winter branches, while in spring and summer, fresher, cooler light highlights the foliage. 

‘The light brings out the colour of the trees. In spring, the leaves are very green and the light is cooler so it looks more vibrant. In autumn, it warms up to bring out the brown of the branches, and because they are silver birch trees, the white bark,’ says Roos.

Thoughtful and atmospheric, the square has clearly been a great asset for workers at Broadgate. Hugely popular at lunchtimes over the summer, in particular in the heatwave, the misting was extended to the delight of park users, with the water feature attracting parents with young families after the word got around on social media, turning the cascade into a children’s splash pool. 

The only shame is that, after so much care taken over the design and lighting, the transformed square is not better signposted or accessed from the station or Liverpool Street itself. Hopefully, however this may be addressed in the station’s upcoming refurbishment.