6. DEMOLITION OF SPECIAL STRUCTURES
If a basement, cellar, vault or void adjoins another property, any adjoining walls should be inspected by a competent person to determine whether they are strong enough to withstand the resultant ground pressure. If they are not, the proposed methods of strengthening them should be subject to an assessment by a competent person( for example, a structural engineer).
If a basement has been built in ground with a high water table, measures should be taken, as far as is reasonably practicable, to prevent any collapse as a result of hydraulic pressure, uncontrolled water inrush or flotation.
If work is to be undertaken in a basement, it will be necessary to determine if the basement is a confined space. There are specific requirements in the WHS Regulations for working in confined spaces. Further information can be found in the Code of Practice: Confined Spaces.
6.5 Masonry and brick arches
Masonry and brick arches should be demolished in a sequence that allows for the removal of as much of the dead load material as possible without interfering with the stability of the main arch rings. The spandrel infilling should only be removed down to the springing line as the load-carrying capacity of many old arches relies on the filling between the spandrels. In multi-span arches, lateral restraints should be provided at the springing level before individual spans are removed.
6.6 Independent chimneys and spires
A detailed inspection and survey should be completed prior to the demolition of a chimney or spire. In particular, the condition of the structural material, which can range from stone and brick to steel, timber and concrete, needs to be assessed to identify any faults, such as fractured or badly weathered stone or rotten timbers.
Measurements may need to be taken to determine whether there is any deviation from the perpendicular. The possibility of chimney instability resulting from inclement weather( for example, high winds) needs to be considered during all stages of demolition work.
Due to their height, it is common for chimneys to be demolished by hand or through induced collapse. Temporary supports may be required to ensure that premature collapse does not occur.
Hand demolition should be carried out progressively from the top of the chimney and from safe working platforms.
Due to their height, control measures that need to be considered when demolishing chimneys or spires include:
• temporary work platforms
• falling object protection •exclusion zones •dust control.
Induced collapse will require sufficient clear space, approximately 1.5 times the total height of the chimney and of sufficient width depending on the type of structure.
34 CODE OF PRACTICE | DEMOLITION WORK