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Worker injured by collapsed roof

In July 2019, a 22 year old man was seriously injured while doing demolition work. At the time, workers were manually demolishing the roof frame and external walls of a single storey home. The truss top plate (also called an upper wall plate) was cut. The top plate is a horizontal load-bearing member secured to the top of the wall studs that supports the roof structure. The roof and external wall frames skewed and fell, trapping the injured worker underneath.

Investigations are continuing.

Preventing a similar incident

Many of the hazards associated with major demolition works are relevant for manual demolition as well. These include;

  • collapse of the structure or part of the structure
  • power lines and other services
  • falls
  • falling objects and debris
  • manual handling
  • exposure to noise, dust, asbestos and hazardous chemicals.

To manage the risk of unexpected collapse, the condition of roofs, walls and floors should be assessed by a competent person before commencing demolition work.

Structures which are not carrying their design loads may be pre-weakened prior to deliberate collapse. This pre-weakening should be carefully planned so that, despite the removal or partial cutting of load-bearing members, the remaining structure has sufficient strength to withstand any wind or impact loads until the actual collapse is initiated.

Risk management must be completed and safe systems of work in place before starting any demolition work.

House demolition which includes work around load bearing areas or is related to the physical integrity of the structure is considered high risk. That means the person conducting a business or undertaking must ensure a safe work method statement for the proposed work is prepared or prepared by another person before starting the job.

Effective risk management starts with a commitment to health and safety from those who operate and manage the business or undertaking.

Managing work health and safety risks is an ongoing process. Risk management involves four steps;

  • identify hazards – find out what could cause harm
  • assess risks – understand the possible harm, how serious it could be, and the likelihood of it happening
  • control risks – implement the most effective control measure that is reasonably practicable in the circumstances
  • review control measures to ensure they are working as planned.

When assessing the risks associated with manual demolition work, consider the following;

  • the structure or part of a 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 the demolition sequence and the effect on stability
  • if any temporary bracing is required to maintain the stability of all parts of the structure and clear instruction for the temporary bracing
  • the layout of the workplace, including whether there are fall hazards both for people and objects
  • what plant and equipment will be used, and the skill and experience required by the people who will use it
  • what exposures might occur, such as noise or ultraviolet (UV) rays
  • the number of people involved
  • local weather conditions.

Once the risks have been assessed, the next step is to control risks. These control measures are ranked from the highest level of protection and reliability to the lowest (hierarchy of control). The WHS Regulation 2011 requires PCBU's to work through this hierarchy to choose the control that most effectively eliminates or, where that is not reasonably practicable, minimises the risk in the circumstances.

You must always aim to eliminate a hazard, which is the most effective control. If this is not reasonably practicable, you must minimise the risk by one or a combination of the following:

  • Substitution - substitute the system of demolition for a domestic premise. For example;
    • using a mechanical demolition method (which involves the use of powered mobile plant, such as excavators, cranes and bulldozers) rather than a manual method, if it is safer.
  • Engineering - the building or structure to be demolished and all its components should be maintained in a safe and structurally stable condition so as to prevent the unexpected collapse of part or all the structure. For example;
    • temporary braces
    • propping
    • shoring or guys may need to be added to ensure stability of the structure is maintained.
  • Administrative controls - if risk remains, it must be minimised by implementing administrative controls, so far as is reasonably practicable. For example;
    • install warning signs
    • establishing exclusion zones around the demolition work.
  • Personal protective equipment - any remaining risk must be minimised with suitable personal protective equipment. For example;
    • provision of hard hats, steel cap boots, high visibility vests.

Note: Administrative control measures and PPE rely on human behaviour and supervision, and used on their own, tend to be least effective in minimising risks.

The control measures that are put in place to protect health and safety should be regularly reviewed to make sure they are effective.

Common review methods include workplace inspection, consultation, testing and analysing records and data. When reviewing control measures, the SWMS must also be reviewed and revised.

If problems are found, go back through the risk management steps, review your information and make further decisions about control measures.


Since 2014, there have been 29 workers' compensation claims accepted involving roof collapses.

In the same period, WHSQ has been notified of 45 events involving the collapse of, or other failure of, a roof and/or wall of a building or failure of a roof. Of those, four (9%) led to injury or illness which required hospitalisation. WHSQ has also issued 45 notices.

Prosecutions and compliance

In 2013, a company was fined $50,000 when a worker's leg and two fingers were crushed. The worker was cutting walls and roof sections at a demolition site. Two walls had been cut and one of them removed, which left an unstable section of the roof. When the worker completed the last cut, this section fell onto him.

More Information

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