Collapsed roof traps and injures worker

A worker has been seriously injured while manually demolishing the roof frame and external walls of a single-storey house. The roof and external wall frames fell after the upper wall plate — a horizontal load-bearing member that supports the roof structure — was cut, trapping the injured worker underneath, according to Workplace Health and Safety (WHS) Queensland. While investigations are continuing, WHS Queensland warned that there are several hazards associated with manual demolition work, including: structure collapse, powerlines and other services, falls, falling objects and debris, manual handling and exposure to noise, dust, asbestos and hazardous chemicals.

To control the risk of unexpected collapse, the condition of roofs, walls and floors should be assessed by a competent person before starting demolition work, WHS Queensland advised. Risk management and implementation of a safe system of work should also be completed before starting work. Structures that are not carrying their design loads may be pre-weakened prior to deliberate collapse. This should be carefully planned so that the structure is strong enough to withstand any wind or impact loads until collapse is initiated, despite its load-bearing members being removed or partially cut.

WHS Queensland added that house demolition that includes work around load-bearing areas or is related to the physical integrity of the structure is considered high risk and that a person conducting a business or undertaking (PCBU) must ensure a safe work method statement for the proposed work is drawn up before starting the job. When assessing risks associated with manual demolition, workers and PCBUs should consider the structure to be demolished and its structural integrity at all stages of demolition, the competent person’s assessment of loadings at all stages of demolition, the method of demolition — including its sequence and effect on stability — and whether any temporary bracing is required to maintain the structure’s stability.

The workplace’s layout and potential hazards should also be considered, as well as which plants and equipment will be used and the skill and experience required by users, what exposure might occur, including noise or ultraviolet (UV) rays, the number of people involved and local weather conditions. These risks should be controlled using measures that offer the highest possible protection and reliability, according to the hierarchy of control, under the WHS Regulation 2011. Workers and PCBUs must always aim to eliminate a hazard; however, if this is not reasonably practicable, they may choose to substitute manual demolition for a mechanical method which involves use of a powered mobile plant, such as excavators, cranes or bulldozers if it is safer.

Additionally, temporary bracing, propping or shoring can be used to help maintain the structure’s stability and prevent the unexpected collapse of all or part of the structure. If risk remains, PCBUs must implement administrative controls such as warning signs and establishing exclusion zones around the demolition work. Finally, any residual risk must be minimised with suitable personal protective equipment, such as hard hats, steel cap boots and high visibility vests. Workers and PCBUs should regularly review these control methods, along with the safe work method statement, via workplace inspection, consultation or testing and analysing records and data to ensure they remain effective.

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