Builders and contractors are being urged to ensure metal deck formwork systems are installed and inspected in accordance with the design instructions following two notifiable dangerous incidents where single prop formwork systems have collapsed during a concrete pour.

In the past few weeks, SafeWork SA has been notified of two notifiable dangerous incidents where single prop formwork systems have collapsed during a concrete pour.

On November 5, while pouring concrete onto the second floor, a formwork section collapsed falling approximately three metres. Eleven workers were in the vicinity at the time of the incident.

Initial enquiries found inadequate propping to support the weight of the load and that the formwork and supporting structures system had not been inspected and certified by a competent person against the design specifications to ensure the system was structurally sound.

On October 25, a formwork section collapsed during a concrete pour. A worker who was vibrating the concrete jumped backwards and was grabbed by another worker after they felt the top flooring sheets fall.

While the formwork and supporting structures system had been inspected and certified by a competent person as structurally sound 10 days before the incident, initial enquiries found inadequate propping to support the weight of the load.

A concrete pre-pour checklist failed to identify that 11 props were either not installed or had been removed.

The construction site following the 5 November collapse.

Single prop formwork systems are always at risk of collapse as opposed to scaffold or form work frame systems. When single props are used, they must be secured, such as bolting the base plate to the slab if one exists or nailed to a large sole board or 6”x 4” timber or LVL.

SafeWork SA Executive Director Martyn Campbell said builders and contractors have a duty to ensure the provision and maintenance of safe plant and structures.

‘While no serious injuries were sustained in any of the recent incidents, they all had the potential to cause major trauma or death,’ he said.

'Businesses must consider all “reasonably practicable” control measures to manage the risk of a formwork collapse. Single prop systems are probably quicker and use less material but they are far more likely to fail if installed incorrectly.

‘Certification that the formwork complies with Australian Standards 3610: Formwork for concrete, and the design should only be provided upon completion of the formwork, including the completion of rectification works and re-inspection of any identified issues.’

Reasonably Practicable Control Measures

Builders and contractors must consider all reasonably practicable controls to manage the risk of a formwork collapse.

These controls include:

  • ensuring that a competent person designs the formwork to retain its shape and withstand loads such as reinforcing, concrete and other associated materials and the dynamic loads imposed by pouring, vibrating, the movement of people or plant or environmental factors such as wind and rain
  • installing the formwork in accordance with the design and instructions from the designer - formwork should be rigid, watertight, braced and tied together to maintain position and shape during construction
  • checking variations to the design and ensure they are verified in writing by the designer, engineer or other competent person
  • not mixing components from different formwork systems
  • putting measures in place (e.g., bracing), to prevent vertical support feet, on inclined surfaces, from slipping
  • before loading with weight, ensuring that a competent person (e.g. an engineer with experience in structural design -certifying engineer) inspects and certifies completed formwork and its supporting structures meet the design specifications and are structurally sound
  • placing concrete in accordance with the specified sequence and pour rate in order to maintain the stability of the formwork
  • monitoring formwork as it is being loaded to check for signs of potential failure or collapse and to ensure vertical and horizontal movements do not exceed specifications; and
  • providing all workers with information and training specific to the formwork system, including:
    • details of the formwork system, tasks, activities and components
    • design intention regarding installation, use, movement, alterations and dismantling
    • control measures to minimise identified risks
    • how to inspect materials used in the formwork system.

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