Formwork for flight of concrete spiral stairs - adjusts to flight depths by varying riser depths and overall step heights

摘要

formwork for a reinforced concrete spiral staircase constitutes the shuttering for a floor to floor flight, and can be adjusted to suit variations in flight depth, such as those occasioned by variations in floor construction depths, and assimilated by varying step levels and riser depths. The assembly comprises a sub-frame, a fixed integral step soffit former, a former for the core and tread surfaces, and the system of adjustable formers for riser faces. The sub-frame may be mounted on wheels to facilitate shutter striking and travel. The riser formers are mounted on arms (21) which radiate from a vertical support spindle (18). Each arm (21) may be built onto a sleeve (20) which can turn on the spindle. The vertical pitch of the arms (21) may be varied by shins (23) between the sleeves (20).