The £5.2 million building has a unique curved glazing system which retracts into the ground and forms the final element in the redevelopment of London’s Duke of York Square, housing a restaurant and incorporating a new rooftop garden
Cadogan Estates commissioned London practice NEX to design the restaurant building as a new focal point for the square. Its design took as its point of departure a nearby Grade II listed wall – originally part of an earlier military asylum on the site.
The restaurant’s spiralling form has an off-white, precast exposed concrete structure in which is set a series of curved glass openings which can descend into the basement below, opening up the ground floor to the surrounding square.
The pavilion’s interior has terrazzo flooring and an ash-wood slatted ceiling which contrasts with the exposed concrete structure. The fit-out of the 100-cover restaurant was completed by Box 9 Design and Rebecca Richwhite, in partnership with Laura Harper-Hinton, co-founder and creative director of Caravan Restaurants.
A curved staircase leads to a public timber-decked roof garden above the restaurant, while the basement contains the kitche, a private dining room, WCs and plant.
The practice won the job through a Malcolm Reading Consultants-organised competition in 2012, beating Architecture 00, Carmody Groarke, Duggan Morris, TaylorSnell and Pernilla Ohrstedt.
Despite its relatively small scale, the restaurant is the result of a long design process. The glazing system alone amounted to around 2,500 hours of research and development. Although similar retraction systems have been installed outside the UK, all have used straight panels. This makes the restaurant the first example of a retractable curved glass system in the world. Its mechanism, though, is as strikingly simple as that of a weighted sash window, with the glazing sliding down into a basement trench where large steel counterweights are housed.
The restaurant uses a semi-passive system to maximise performance and minimise energy use. The public areas are designed to be naturally ventilated throughout the year – either with the windows partially or fully retracted in fine weather, or with a 50mm opening at the top at other times for natural ventilation. An air source heat pump supplies heating in colder months. The precast concrete structure with its planted roof garden has a high thermal mass, while the glazing system has good environmental credentials and exceptional airtightness levels thanks to a bespoke sealing system. With its dedication to sustainability, the building achieves BREEAM Excellent and is one of the greenest restaurant buildings in London.
Alan Dempsey, director, NEX Architecture
The structural ribbon acts as the main vertical and horizontal resisting element. It provides vertical support to the roof terrace slab, as well as inner and outer support to the roof terrace stair. The ribbon, having curled in on itself at the centre of the building, forms a robust stability core, where a lift, dumb-waiters and services can be elegantly hidden from direct view. AKT II’s in-house developed software, re.AKT, was used to quickly import and export the ribbon geometry into various finite element software, Rhino and Revit. This enabled AKT II to quickly assess structural performance resulting from iterations in the design, as well as quickly reacting to the changes in setting out of the individual panels as the project neared the construction phase. The architectural intent called for the openings in the curved ribbon to be projections into the building, and as such increased the amount of setting-out points per panel two-fold. A total of 2,369 setting-out points were used to ensure the precise casting of the 30 ribbon panels.
The ribbon, a multifunctional element, was required to be load-bearing, act as the building façade, and be of exceptional architectural finish. AKT II’s p.art team undertook parametric studies in collaboration with Nex in efforts to rationalise the ribbon to find savings by way of repetition and modularity. Studies emphasised breaking the ribbon into a finite number to standard radii and lengths in order to minimise the number of moulds necessary to form the panels. As a result of the parametric study, the number of precast moulds on the project reduced by 17 per cent, bringing significant savings.
AKT II negotiated deftly between slenderness, durability, and constructability to achieve the feature white precast ribbon. The Duke of York Restaurant has been a success for AKT II in many ways. Constructing this new piece of Chelsea required the demolition of one of our original phase 1 buildings, a mark of the success of the development, yet we are pleased to have been involved in the creation of a new award-winning piece of Architecture with Nex, which underscores the Cadogan Estates continuing commitment to design and quality. In this unique building, we have the opportunity to showcase AKT II’s strength and dexterity in refined engineering, innovation and complex geometry.
Start on site June 2017
Completion date Summer 2019
Gross (internal + external) floor area 640m2
Gross (external) floor area 960m2
Form of contract or procurement route Traditional
Construction cost £5.2 million
Client Cadogan Estates
Structural engineer AKT II
M&E consultant E+M Tecnica
Quantity surveyor Equals (pre-tender); TTTP (construction)
Lighting design DHA Design
Planning consultant Gerald Eve
Landscape consultant Bradley Hole Schoenach BHSLA
Project manager Capital and Provincial
CDM co-ordinator Shore Engineering
Approved building inspector RBCK
Main contractor Westgreen
CAD software used Revit, Rhino
Annual CO2 emissions 55.9kgCO2/m²/yr
Nex’s original 2012 design for the pavilion in Cadogan Square