With back-step method and bracing

Great precision required in construction of new warehouse next to existing building

Data & Facts

  • Project
    • New warehouse in Münchenbuchsee, Switzerland
  • Principal
    • kiener und wittlin AG
  • Contractor
    • Marti AG, Bern, Switzerland
  • MEVA systems
    • Mammut XT wall formwork
    • SecuritBasic safety system
  • Engineering and support
    • MEVA Schalungs-Systeme AG, Seon, Switzerland

138 meters in 24 stages

During the construction of a new warehouse in Switzerland, the erection of the initial formwork directly next to the adjacent building was performed without a hitch. The Mammut XT wall formwork system with single-sided tying did an excellent job.

In Münchenbuchsee near Bern, Marti AG was commissioned by the building materials supplier kiener + wittlin AG with the construction of a large, 15-meter-high warehouse with an area of approximately 2,500 m2. The high wall sections were no problem for Mammut XT’s high-performance formwork panels with a fresh-concrete pressure capacity of 100 kN/m2. However, special precautionary measures had to be taken, as the walls of the new warehouse were situated directly adjacent to an existing warehouse.

700 m2 of Mammut XT panels and the modular safety system SecuritBasic were used on the construction site between November 2019 and February 2020. The team led by the senior construction foreman Reto Kiener decided to build the walls using the back-step method, in which, after pouring each wall section, the next section is skipped, and when the adjacent sections have hardened, the resulting gaps are reinforced and then filled in with concrete. The advantage of this method is the efficient use of formwork material and thus the reduction of the formwork costs.

138 meters in 24 stages
Two separate concreting sections with a width of 5.75 m and a height of 14.74 m were created in twelve stages. A total of three walls that were connected to form an h-shape had to be poured using double-sided formwork over a length of 138 m, partly alongside the existing building. The upper section of the adjacent warehouse’s façade is made up of not particularly robust fibre-cement sheets and overhangs by up to 25 cm.

“The gap of only 60 to 80 cm between the walls of the existing warehouse and our formwork was a challenge,” explains MEVA’s Raphael Klauser. “It was, of course, not possible to support the initial formwork from the rear, which meant we had to secure the initial and final formwork in the new floor slab using bracing.” This bracing was created using reinforced alignment rails attached to the Mammut XT panels.

The simple and quick single-sided tying option provided by MEVA’s integrated combination tie hole was a huge advantage during construction of the large-format concrete walls in conjunction with the lack of space in which to work behind the initial formwork. This enabled the formwork to be erected approximately 20% faster than comparable competitors' systems – as confirmed by an independent authority (Manual on Work Organisation for Construction Projects – Forming Work, Frame Formwork, Walls 2019).

Firmly attached with multi-function profiles
The SecuritBasic safety system with non-slip aluminium checkered sheeting ensured safety when working at heights. The modular system meets stringent statutory safety requirements, such as the accident prevention regulations issued by Suva, the Swiss national accident insurance fund. The walkway bracket on the working platform – like all MEVA accessories – is simply attached to the multi-function profiles of the Mammut XT panels with the flange screw. It can be installed quickly and easily on the ground, and the complete units are then moved into position by crane. The multi-function profiles were frequently required at the construction site in Münchenbuchsee, as they ensured that both SecuritBasic and the alignment rails were firmly attached to provide the bracing.

“The construction work proceeded safety and according to plan,” reports the senior construction foreman Reto Kiener. The last of the twelve back-step stages were poured at the start of February 2020. Just a few weeks later the new warehouse was officially opened.