Slip forming

Slip forming is a fast, cost-efficient and traditional construction method that replaces the customary use of system or constructed forms and allows seamless structures. Slip forming is used especially in high construction projects of tens or hundreds of metres. Projects under 25 metres are usually carried out using other construction techniques. The shaft of Näsinneula, the Neste tower in Keilaniemi and many well-known concrete water towers and smoke stacks have been manufactured using slip forming.

Forms of varying size and shape are moved up with jacks, allowing the realisation of significant schedule and cost benefits. The form moves up at a daily rate of roughly five metres, together with the scaffolding carrying the workers. As the form ascends, the team works continuously to make a structure, such as a smoke stack or staircase tower, out of concrete and iron, and the work continues almost without breaks until the target height. After that, the form, along with its scaffolding and tools, is lowered down.

Slip forming is usually done in two or three shifts, but it may also be scheduled to continue without breaks from the beginning to the end to prevent the formation of working joints. When one shift finishes, another takes over without interruption. For weekends, the work is often interrupted, unless the engineer requires otherwise. 

Frame erection, for example, can be brought forward by constructing the stair towers by means of slip forming. Slip forming can also be used for the extension of buildings down to the underlying rock space. In addition to YIT, only one other operator in Finland has the special competence required for slip forming. In projects for which slip forming is suitable, it is usually the fastest, most economical and strongest technique available.

Slip forming can be used for the construction of the following, for example

      • Water towers
      • Lift shafts and staircase shafts
      • Silos
      • Tanks and bunkers
      • Smoke stacks and exhaust air chimneys
      • Caissons and quay elements
      • Wind power station foundations

How to do slip form?