[WORKING DETAIL 25.06.09] Atrium roof detail
New Stobhill Hospital − Instead of a simple glazed roof over the atrium of the New Stobhill Hospital, specific zones introduce different levels of natural light. To maximise the quality and level of daylight and to stop structural bracing diminishing the spatial clarity, this design required careful and detailed resolution.
To avoid friction forces and optimise the structure, a conventional sliding joint was abandoned in favour of a strut contained within one leg of the portal frame. The strut, inspired by the prop shaft of the project engineer’s Morris Minor, was connected at the top and bottom using universal joints to allow free movement.
The primary source of light is a continuous north-facing 3.5m-deep clerestory at roof level. Accents and animation are introduced by admitting controlled light by other means. The horizontal plane of the ceilingscape is relieved by a line of baffles day-lit from above. A narrow clerestory to the south bounces light on to the edge of the ceiling and admits occasional sunlight.
The vertical north clerestory has ‘hockey stick’ steel ribs that turn over to become a horizontal narrow rooflight, directing watery reflections into the space. West and east gables are glazed, bringing shifts in the personality of the lightscape from sunrise to sunset.
The use of standard curtain walling for the roof glazing required a slope of 15°, turning the surface towards the sun and increasing the reflections. The central rooflights are, in fact, smoke vents required for the fire strategy, with transparent louvres.
Andy Law, project director at Reiach and Hall, and John Robson, technical director at SKM Anthony Hunts