Working details A GLASS ROOFLIGHT SET IN A PRECAST CONCRETE WALL
The new building is L-shaped and three storeys high. Its two wings, which house open-plan offices, are of cast-in-situ concrete construction. They come together in a corner link of lightweight steel and glass - the architect refers to it as as a 'knuckle'. The knuckle houses circulation spaces and meeting rooms.
The ground-level wings are bordered by a single-storey wall of precast concrete panels. This is conceived as a reinterpretation of the English collegiate garden wall. However, this apparently freestanding element is in fact the ground-floor facade and is joined to the facade of the upper floors by a concealed glass rooflight. The detail section on the left shows the precast panelled wall at ground-floor level and an upper facade of rendered blockwork, enclosing a landing to the staircase.
The 1175 x 617mm stack-bonded precast concrete panels have an acid-etched finish. They have 20mm open joints to act as a rainscreen; the joints are backed by P-section neoprene gaskets mechanically fixed to the rear of the panels. The panels are fixed to an insulated 140mm blockwork wall with adjustable restraint brackets fixed to steel T-sections.
The rooflight, concealed behind the coping of the precast wall, is of 12mm heat-soaked toughened glass. Its upper edge is housed in an aluminium channel and fixed to the main facade with steel angles. The lower edge drains into a preformed gutter fitted into a steel channel which supports the precast coping stone. Rainwater is discharged into a pipe concealed in the cavity. A row of polyester powder-coated louvres above the rooflight form part of the natural ventilation system.
The meeting room projects beyond the precast panelled wall in the form of a structural glass bay. It consists of sheets of 12mm heat-soaked toughened glass, silicone jointed at the corners.