jackblock construction

Floor slabs are cast at ground level, with the ground floor slab remaining in position throughout and acting as a casting bed for the roof and other floors. After attaining structural strength, the slabs are jacked up by hydraulic rams one storey at a time, roof first, and supporting walls are built between them. This enables finishing and wet trades to work under cover on upper floors while concrete casting takes place at ground level. The name ‘jackblock’ is derived from precision-made concrete blocks which form the supporting walls, equal in height to one stroke of the jacking ram (about 200 mm).