What is demolition?
Demolition is an all-encompassing term for removing all or part of a structure. ‘Structure’ means any fixed or movable construction, permanent or temporary, load-bearing or not. Demolition covers inside and outside buildings, special structures and entire sites. Demolition often involves excavation as well. However it doesn’t include removing the poles of utilities such as electricity, phone lines or lights. All demolition is covered by strict regulations. In some cases, ie. the more dangerous ones, Safe Work Method Statements have to be prepared before any work commences.
Types of demolition
Two main types of demolition are explosive demolition and selective demolition.
Explosive is basically the total destruction of the whole building and removal of all the debris. It prepares a site for something else.
Selective demolition is a detailed demolition of specific parts of buildings and sites. It can be as big as taking down a wing of a hospital, or as small as removing a tiled floor, wall or shed. Interior stripouts is one kind of selective demolition. This involves removing all interior features to provide an empty shell. Another special type of selective demolition is called deconstruction. This is where a building is effectively ‘un-built’. It is taken apart bit by bit in order to salvage as many reusable materials as possible, instead of dumping them in landfill.
Reasons for demolition
You may have any number of reasons for demolishing a structure, such as:
- Every building or structure has a design life - its safe useable lifespan. After that it’s not safe and has to be demolished.
- You may need to demolish old structures and replace them with new ones.
- A building may be damaged and rendered unsafe or unrepairable by fire, storms, floods or termites, for example.
- Or you may wish to demolish a small structure to construct a big one in place of it.
- Real estate investment property development is another reason.
- Home owners may wish to extend or renovate a house.
- Commercial or civil redevelopment projects may necessitate the demolition of structures.
These are the main methods used for demolition:
- manual demolition - by tradespeople wielding small tools
- mechanical demolition - the use of wrecking balls, sledge hammers, bulldozers and high reach excavators
- induced collapse - explosives are set to make a building fall sideways like a tree if there’s enough space
- implosion - placing explosives to make a building collapse in on itself downwards leaving the surroundings untouched
Steps in demolition
There are a series of routine but important steps in any demolition job:
- Surveying - find out and document the method of construction, underground components, condition of the building or structure, the presence of hazardous materials, drainage, type of neighbourhood, etc
- Removal of Hazardous Materials - site inspectors may discover hazardous materials such as asbestos, radioactive metals, petroleum or other toxic chemical contamination. Specially qualified people have to be brought in to remove them before demolition goes ahead.
- Preparation of plan - this plan covers all about the building, its structure, supports, surrounds, public health and safety, debris handling, time course of project, etc
- Safety measures - this includes removing flammables, situating firefighting equipment, putting in place worker health and safety infrastructure, etc.
Only after all these have been done can a demolition go ahead.