Jump form construction
Jump forms are one method for the construction of the cores (that house the lifts, staircases etc.) for high-rise buildings and similar structures. The structure is cast in a series of vertical sections called ´lifts´. After the concrete has gained sufficient strength the formwork is moved back and then ‘jumped’ to the next level above.
The formwork is generally part of a complete system consisting of three or more levels.
1. The upper level is for storage and concreting,
2. The main platform is for fixing the reinforcement and setting the shutters and
3. The lower level gives access to the finished concrete surface, to allow any remedial work and for attaching fixings to cast-in sockets and plates.
For most structures a crane is used to lift the complete assembly to the higher level. However, for larger structures this may be impracticable, requiring the use of self-climbing systems that have built-in hydraulic lifting jacks.