The collapse of structures, including buildings, may result in death or serious injury to employees and the public.
There have been numerous incidents where structures have collapsed. This has been due to:
- inclement weather, particularly wind
- the foundations or temporary supports of the structure being undermined
- lateral supports of the structure being removed
- the structure receiving a heavy impact, or
- any combination of these and other factors.
Incidents have included:
- a portal steel building collapsing during construction
- a house being restumped sliding off its jacks while employees were under the house
- a carport wall under construction collapsing onto sheltering employees during a storm.
Duty holders should monitor the structures under their management and control for adequate stability to ensure employees and members of the public are not put at risk from structural collapse.
Structures should be able to resist extreme weather including high winds and surface water or run-off. They should be capable of withstanding dynamic forces and have solid foundations.
If unstable or likely to become unstable, a suitable large exclusion zone should be established around the structure
until rectification works are completed.
Temporary bracing should be considered if the structure is incomplete or works may affect stability. Where lateral support from piers, cross-walls, floors and roof framework is missing or being altered, temporary bracing should also be used.
Temporary bracing or other stability controls should be designed by a competent person who is experienced in such works eg professional engineer.
To ensure work will not compromise stability, a competent person should be consulted before adding or making changes to or undertaking any structural work on the structure, or before excavating near the structure.
Temporary bracing inspections
A competent person should inspect the temporary bracing arrangements and verify in writing the stability of the structure when the bracing is first installed.
A competent person should regularly assess the stability of the structure while temporary bracing is required. Inspections should be done at regular intervals, based on a risk assessment that takes into account the structure’s condition, environmental factors and length of time the bracing has been in place.
In addition, an inspection should occur as soon as possible after an extreme weather event or other incident that could affect stability.
Changes to stability arrangements
Duty holders should ensure no part of the structure that provides structural support, including temporary bracing, is altered or removed unless specifically approved in writing from a competent person. If the competent person requires additional bracing to be installed to ensure stability, the changes should be made in the sequence specified by the competent person.