Tonkin Liu’s Promenade of Light at Old Street
Tonkin Liu has completed the first part of a three-phase project to upgrade the area around Old Street roundabout in central London
Architect: Tonkin Liu
Location: Old Street, central London
How do you convert an unloved stretch of land into quality urban realm? That was the challenge facing Tonkin Liu on its three projects to improve the area near Old Street roundabout in central London.
The first, the Promenade of Light on Old Street itself, is complete. Work is shortly to start on site for the main element of the second phase, the Mirror Tree, close to the roundabout. A further phase, a longer-term plan for the centre of the roundabout itself and its environs, is at the early stages.
Tonkin Liu won a competition for the 3,455sq m project, its first landscape commission, in 2004. The £1 million scheme is part of the EC1 New Deal for Communities regeneration programme. Client Islington Council was keen for improvements to the 180m-long stretch that would not only enhance the pedestrian journey through the space but also ameliorate the experience for those wanting to sit and linger.
It was an area, warts and all, that partners Mike Tonkin and Anna Liu knew very well as their son’s school and their own office are both nearby.
The practice studied how the site was inhabited and identified several different user groups — workers passing through, OAPs wanting somewhere to sit, parents and young children, resting bike couriers, and shoppers keen to examine their purchases. They quickly realised how important the plane trees on the site were — not just to shield the space from the busy road, but also by providing interesting shadows and, in particular, circular areas of shelter from the rain. “The nicest thing about it was the trees,” says Tonkin. “We wanted to create this ‘room’ under the trees by putting in a second row.”
These 21 mature plane trees were a major factor in the design solution. Having decided to plant a second row of 18 trees of mixed sizes to make a leafy promenade, the architect had to deal with tree root issues. Given the site’s proximity to Moorfields Eye Hospital, it was important that the surface offered no impediments and that there was high contrast between seating and pavement. Tonkin Liu decided to create a 300mm-high camber in the promenade above the roots, plus areas of resin-bonded gravel around the trees and on the camber to allow vital water penetration. Needle piling was used for new seating to avoid interfering with the roots.
Key interventions are the black granite rings around each tree. According to the location, sometimes these are on the ground, sometimes raised as seating or else raised even higher as counters. For example, there is more seating by bus stops, while counter-style surfaces are positioned near shops.
This strong circular theme is picked up in the small gravel inlays in the granite — the architect has made these round and arranged them in circles.
The trees also governed the lighting strategy. Great efforts were made to create interesting shadows on the granite paving through the foliage. Tonkin Liu used Targetti lights mounted close to the trees on 23 tapering lighting columns by Urbis, each with between six and eight multi-directional spotlights. The lower ones provide a yellow safety light while the upper lights give the shadows, each one adjusted by the architect by hand according to a 3D model worked out in advance. The angle of the beams varies between five and 50 degrees.
The promenade had been raised up to require a double-step kerb to deter car incursions, but it was still necessary to add bollards at either end. Colourful planting at the base of the trees enlivens the sober palette.
Chinese granite rings
Chinese granite was specified for the promenade for its robustness and also because of its low price compared with European granites.
We wanted to create this “room”under the trees by putting in a second row
It was supplied by Stonepave UK.
Tonkin Liu chose white and black varieties, white for paving, and black for seating and the border around the promenade.
All pieces were pre-cut in China. Tonkin Liu worked out three different sizes of template for the paving depending on the position of the seating beneath each tree.
For the seats, 120mm-thick granite was assembled to form the ring, with slots to accommodate the small number of iroko timber seats dotted around the project and supplied by Maxwell Pinborough. These were shot-blasted, then stained black so as to blend in with the granite.
According to Aran Chadwick of engineer Atelier One, the foundations for the granite rings was the most difficult aspect of the project because of the large number of roots and fluctuating moisture levels, which cause swelling and settlement.
This is far more of a problem with granite than timber or steel, which have more give. Roots meant that concrete foundations were impossible, so Atelier One suggested micro-piling to a depth of 2.5m to support the steel ring the granite sits on.
Following Tonkin Liu’s Singing Ringing Tree installation in Lancashire, the practice plans a Mirror Tree on a triangle of land owned by Transport for London at the Old Street roundabout end of the new Promenade of Light.
The artwork is being created with Mike Smith Studio, which collaborated on the Singing Ringing Tree. The concept is for a magnolia tree in a planter positioned half in, half out of the ground, which appears to rise out of a hole of light.
It will be surrounded by a bowl of toughened mirror glass that will bounce light around the area.
The bowl, 5m in diameter, will be positioned 700mm off centre from the tree. It will be made up of 22 pieces of self-cleaning glass on an aluminium honeycomb panel, laminated with resin. This will be supported by a galvanised mild steel structure which attaches to a poured concrete base in the ground. Uplighters will be concealed inside the mirror disc. “It’s a bit like putting on an Elizabethan ruff to draw attention to the face,” says Tonkin.
Tonkin Liu was keen for the landscaping to have a seasonal element — the magnolia will bloom twice yearly. The practice also likes the way it will act as a partial screen to the roundabout in its off-centre position at the end of the promenade. As part of this £400,000 second phase, the lighting posts will be continued down past the tree, along with cycle racks, railings and planters.
A new bridge over the underground station entrance has already been completed.
Architect Tonkin Liu, Clients Islington Council/EC1 New Deal/Transport for London, Services & highways engineer Islington Council Transport & Planning, Structural engineers Atelier One and Hyder Consulting (Mirror Tree), Contractors Gabriel Contractors (Promenade of Light) and Ringway Jacobs (Mirror Tree), Artwork fabricator Mike Smith Studio, Tree consultant Civic Trees and Islington Council Greenspace, Lighting supplier Targetti
Old Street photos by Keith Collie