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When a building reaches the end of its useful life through age, poor design or other factors (such as fire damage) it will need to be disposed of. This is usually by demolition.
This can present a variety of environmental challenges as many buildings contain toxic materials such as asbestos as well as bulky heavy waste that will fill up landfills. It is estimated 20% of the solid waste in landfills is construction related.
This has led to new approaches when a building is to be removed from a site, such as deconstruction instead of demolition.
Traditional demolition is a 'simple' process, knock down the building and put the remaining rubble into a landfill site. It is of course a high-risk activity requiring a planned approach involving an engineering survey, a demolition plan, risk assessment and coordination with the contractor.
This is done by a number of means. For smaller buildings heavy plant machinery is used to topple the building by undermining its structural strength. Larger buildings, particularly those in urban areas, are normally bought down by using explosives planted around the structure to collapse the building into itself, allowing it to fall on its own footprint. These methods produce a lot of unusable waste material which will need to be transported off site and dumped into a landfill.-->
Reducing the amount of material wasted is key to a low impact build. When a building already existing on a site is surplus to requirement there is a much more environmentally friendly method than traditional recycling. This method is commonly known as 'deconstruction'.
Deconstruction is almost the reverse of construction, instead of simply razing a building quickly it is taken apart systematically preventing damage to the building materials. Starting internally, doors, fittings and fixtures are removed in order to be reused. Copper wiring and pipework is then removed for either recycling as a material or smelting down to create new material. Once the internals of a building has been stripped out work begins on the structure. Timber roof supports will be taken down for reuse in new buildings after roof slates have been removed to be reused.
When this is done work can commence on removing the brickwork for reuse. Bricks have a long life when cared for and the colour change during their ageing can be desirable when adding character to a new build. It is currently estimated that 150 million of 2,500million bricks are reclaimed (around 6%).
While de-constructing a building saves a lot of natural resources being used, it is a slower and therefore more costly method then traditional demolition. Deconstruction does have other benefits other than the obvious environmental ones. By de-constructing and using the materials on site, transportation costs are saved, allowing a reduction of carbon emissions and offsetting some of the extra cost.
The cost of tipping fees will also be negated or reduced depending on the level of deconstruction, as less material will be sent to the landfill. Materials left over from a de-constructed building that are not required on site can either be sold on or donated to charity projects (which may be tax deductible) allowing a resource that would normally cost builders to dispose of to potentially produce a small revenue.
Whichever method of removing a building from a site is used care and consideration needs to be taken to make sure toxic materials are removed and disposed of safely.
Asbestos was a commonly used building material up until the 1980s. It has been found to carry health risks such as lung cancer and other respiratory diseases. If asbestos is found on the site it will need to be disposed of as hazard waste and should not be cut, drilled or milled and precautions should be taken to prevent any asbestos dust from forming. Asbestos can not be disposed of with ordinary rubbish so local authorities should be contacted for details of where to dispose of it.
Other toxic materials that can be contained in buildings for demolition/deconstruction include lead paint, fluorescent lighting, mercury from switches and some forms of plastic insulation. Also any old fittings such as refrigeration units etc. will have to be disposed of carefully and legally to prevent toxic waste. These will all require more costly disposal methods to ensure environmental safety and to comply with local laws.
The removal of old buildings is a necessity. However by using slower, more labour intensive techniques, such as deconstruction, it is possible to reduce the need for new materials in builds (420 million tonnes of new material each year). It also cuts the amount required to be sent to already overfilled landfills, as well as saving road mileage and therefore CO2.
All of these benefits mean that deconstruction is by far the best choice for removing old buildings for both the green builder and the construction industry as a whole.