Working details A PROJECTING ROOF SUPPORTED BY A STRUCTURAL DOWNPIPE
The new primary school is on a restricted site in a residential area. To accommodate the classrooms required, a building of two storeys was necessary, but to minimise intrusion to the residential area, the floor-to-ceiling heights were kept as low as possible (2.4m), and the roof was designed with a very shallow pitch of 2degrees, with deep overhangs.
The low floor-to-ceiling height was seen as a means of creating a suitable scale for young children. It also allowed the use of ramps, rather than stairs or lifts, to reach the first floor. Light and ventilation to the back of the classrooms are provided by skylights or 'lightscoops'.
To reduce the overall height of the building, the cast-in-situ concrete first-floor slab is power-floated to 300mm deep, and its soffit is grit- blasted to act as part of the ground-floor ceiling finish. The suspended ceiling to the first floor, made from mdf sheets on timber studwork, is only 200mm deep.
The roof is of standing-seam Kal-zip aluminium supported by timber joists. On the south elevation the ground and first floor are fully glazed with an aluminium window system. The lower sections of the double-glazed units are fritted with dots to shade the classroom from direct sunlight and to obscure the sight of furniture set against the glass.
Additional protection from solar gain is given by the overhanging roof and the first-floor slab, which project beyond the ground-floor wall. An aluminium box gutter runs behind the eaves fascia, which is supported by a series of structural rainwater downpipes. They are 168.3mm-diameter chss, each stiffened with a welded 10mm steel plate. Slabs of 200 x 50mm teak are fixed to the plates to create a protective cushion. Each downpipe terminates above the gulley to allow cleaning.