Dennis Gilbert, Marcus Peel
Forming the final stages of a ten-year masterplan, Walters & Cohen Architects and Orms have respectively completed a new arts building and combined swimming pool and fitness centre at the American School in London (ASL). Occupying a prominent corner plot in the St John’s Wood conservation area, the 1200-square-metre arts building comprises an exhibition space on the ground floor, with art, sculpture, ceramics and photography studios on the upper levels. Naturally lit from the north and south, the open-plan studios combine rubber and/or timber floors with white plastered walls and easily moveable furniture for increased flexibility.
Taking its cue from the mass and footprint of the surrounding listed semi-detached villas, the building is intended to resemble a single large property. Clad with fluted Portuguese limestone, the facade features large vertical window bays incorporating projecting architectural bronze profiles. Each block of limestone has been cut to an individual pattern, creating a gradual fade motif on the vertical flutes. This changes from a depth of 20mm at the base to completely flat at parapet level. The stone mason’s expertise in 3D-modellling made a non-linear reduction possible across the facade, says the architect. This allowed the depth of the flute to remain greater for the first two-thirds of its length, before tapering more quickly above the head of the windows. The overall effect is a visually arresting pattern that changes throughout the day.
Structurally, the scheme employs an in-situ concrete frame to bridge over a Victorian brick railway tunnel that is located directly below the site. This not only obviates the need for movement joints, but also ensures large, column-free floor plates. The high-grade, fair-faced concrete is left exposed internally to promote thermal mass and night-time cooling.
The majority of Orms’ 1430-square-metre pool and fitness centre is located at lower-ground level beneath an existing playground. Clad with glass tiles to reflect daylight, and providing glimpsed views across the pool, a curved changing room block is located in the centre of the plan. Generous floor-to-ceiling heights have been achieved in the 25×12-metre pool hall, fitness room and multi-purpose space by excavating the site to a depth of 10 metres. A triple-height light-scoop located at ground level illuminates the spectator gallery below. The building also provides underground access to Walters & Cohen’s arts building, as well as a new suite of science rooms by Ed Toovey Architects.
Central to the scheme is the exposed concrete soffit forming the underside of the playground and the internal timber-clad acoustic wall linking the primary below-ground spaces. The lightest possible concrete colour mix was chosen to maximise natural and artificial light reflection, says the architect. Shuttering board layouts, recesses and hidden service routes were refined with the subcontractor to achieve a clean, uncluttered appearance. Lime-washed Hemlock was chosen to face the acoustic wall for its performance in pool environments, and light, bright aesthetic.
Providing access to both the subterranean sports facilities and adjacent playground, the building’s glass and timber facade has been inserted beneath an existing first-floor classroom block. Planned around a formal grid relating to the fenestration above, the facade is a conscious contrast to the solid brick wall that preceded it. Slatted timber cladding panels are designed to give a sense of scale and warmth, while the aluminium glazing system features a bespoke capping piece designed by the architect.