Masonry structures - Instability leads to collapse

Background

The collapse of masonry structures during construction, renovation and demolition at Victorian construction sites have sometimes resulted in death and serious injury.

The incidents, listed below, highlight the dangers of unstable or inadequately braced masonry structures, such as walls of brick, stone and concrete blocks, when subjected to horizontal forces such as high wind or impact.

• A party block wall, under construction, collapsed during windy conditions.
• A carport wall, under construction, collapsed during a storm onto two workers.
• A second floor block wall, under construction, collapsed and brought down a whole building (pictured).
• While digging a shallow trench, the wall next to the trench collapsed onto the worker, due to undermining.
• A brick chimney collapsed on to a worker during roof works.
• A 4 m high, double leaf perimeter wall, with no support piers, was blown over onto a road.

Recommendations

Builders, bricklayer contractors and other employers involved in construction, alteration or demolition works of, or near masonry walls and structures, must ensure that these structures have adequate strength and stability. The structures must also be able to resist the effects of extreme weather conditions during these works.

Many masonry structures gain stability from other structural components such as cross walls, floor and roof framework and support piers. When structures are incomplete and are not supported by these means, or these support elements are being removed or altered, adequate temporary bracing is required.

During works:

• Make sure that construction of masonry does not proceed too quickly to allow mortar to develop full strength.
• Before commencing renovation or demolition works near masonry structures, assess the current stability of the structure and the effect that the works will have on the stability of the structures. Develop a schedule of work so activities only occur when it is safe.
• Provide temporary bracing for incomplete or potentially unstable masonry, capable of stabilising the structure, where the mortar has not reached full strength or where the lateral support from returns (cross walls), floor or roof framework is not yet provided or is being removed or altered.
• Do not carry out work during extreme weather conditions.

Detailed recommendations on temporary bracing during construction of masonry walls can be found in Australian Standard AS 3700 - Masonry structures and in Masonry Structures - Commentary (Supplement to AS 3700), section C11.9.

Note: Under Part 5 of the Occupational Health and Safety Act 2004, employers must notify the WorkSafe Victoria of the collapse or partial collapse of any part of a building or structure.

Acts and Regulations

• Occupational Health and Safety Act 2004

Standards Australia

Listed below, are relevant Australian Standards:

• Australian Standard AS 3700 - Masonry structures
• Australian Standard AS 3700 - Masonry structures - Commentary (Supplement to AS3700).
• Australian Standard AS 1170.2 - Minimum Design loads on Structures, part 2: Wind Loads