August 28th, 2011 by admin
Introduction
The definition of the term ‘demolish’ is deliberate and controlled collapse of a structure. During the late 1970′s Fred Dibnah took over as the most well-known steeplejack in The British Isles when his work on demolishing large chimneys without having the requirement for explosives was shown on Tv. Fred was an interesting figure and became famed as an expert on restoring tall chimneys, so when it came to taking them down he knew precisely how to acheive it. He normally would cut an alcove at the foot of the chimney, and then place wooden props to hold the structure. By means of properly positioning the props, the chimney would be likely to fall in the correct place when the wood was set alight and burned away. Once he was almost killed because he miscalculated slightly, demonstrating just how dangerous demolition work truly is.
The particular term to demolish only came into being in 1570, and was used there after to mean the deliberate taking down or destroying of a building or structure. Even though in reality the process of demolition, in some mode or other, has been taking place for millenia. Buildings were destroyed either by natural disturbances of the Earth’s crust or during battles or assaults on towns for as long as there have been structures. The left over wrecks would be removed and rebuilt or used by other structures in the area and must be early types of recycling.
Preserving the Past – Preparing the Future.
To conserve The UK’s tradition of agriculture the farm land between the built up areas of the villages and towns is protected from development of urban sprawl. This land is called Green Belt and it is preserved for farming that is vital to the continuing financial state of the country. By protecting the Green Belt, urban areas are being squeezed for the provision of housing, so developers have to be a lot more innovative to discover acceptable sites.
Great Britain is a nation with an extremely dense population per square mile. The amount of land readily available for development is restricted in comparison to other countries. Consequently there is always a healthy demand for space on which to build. Taking down outdated and abandoned properties and replacing them with brand-new is an excellent method to attempt to counter this general shortage.
Land which may be disused industrial and commercial sites, but could possibly be contaminated with harmful waste or pollution, are known as Brownfield sites. Once the land has been cleaned up they’re potentially valuable for redevelopment. Both Glasgow and South Wales created gardens using disused industrial sites and installed Shopping centres to attract holidaymakers and visitors and generate income.
Greyfield sites are totally different to Brownfield sites in that they don’t possess the environmental concerns of harmful waste. The term greyfield originates from the large areas of asphalt that had once been car parks of commercial urban units. Their worth is in the indisputable fact that the commercial infrastructure such as roads, electricity, water supply, sewerage, and gas is already available. These types of urban areas which become under-utilised or abandoned and are valuable because they require little or no remedial work to be renovated. Cities such as Leeds and Manchester have had an enormous programme of changing the old warehouses or factories into homes, shops and cafes, retaining the main shell and refurbishing the interior into modern accommodation.
The Demolition Process
Any experienced and professional demolition contractor should be able to make an assessment of the following basic items.
The design type and physical size of the structure.
What elements have re-use value?
What will the cleaned site’s re-use be intended for?
Where are the waste by-products going to be disposed?
What precautions need to be made with regards electricity, water, sewerage and gas mains.
Hydraulic excavators and bulldozers are often used to undermine the walls at the foundation, so the building will topple; at the same time managing the manner and direction of the fall. Safety issues are very important, and clean-up strategies are usually considered when choosing the way the building will be demolished.
Old fashioned Demolition
In the old days the standard manner of demolishing a structure was very primitive. Once the services were turned off, the men and machinery would expect to go ahead and simply knock down the walls. Then the complete framework would fall and then the resulting debris could be piled onto lorries and be dumped in land fill sites. Concrete foundations were broken up by pneumatic tools and the site could be cleaned of waste ready for the new work to start. Then again nowadays demolition activities are at the mercy of rigorous planning, safety and inspection laws and are also heavily governed by the local authority. How a building is constructed will mean that one part depends on the other for stability and strength. For instance the rooftop of a property is not really fastened down apart from fixing tiles with nails to stop them slipping. The rooftop stays in place using its own weight because the beams are laid on top of the walls rather than being fixed into them like they were in the past for much older properties. The cross beams and purlins then link the entire thing together to secure the frame of the roofing. To this slats are laid as a frame for laying on the tiles or slates. Other sections of a building are also interdependent so when it comes to demolition these factors are considered in the sequence of deconstruction. In a sense, like Fred Dibnah you need to be an expert in construction to know how to carry out the deconstruction.
Deconstruction and Recycling
The modern method of demolishing buildings is known as deconstruction – an environmentally friendly approach. Landfill sites are in limited supply therefore the aim when demolishing a property is to minimise the quantity of waste material remaining.
Small constructions for instance two or three storey houses can be disassembled quite easily. The work may be a painstaking task of dismantling manually – brick by brick – or beam by beam but by proceeding cautiously valuable components are safeguarded for re-use. The beauty of deconstruction is that 90% or even more of waste materials is prevented from going directly into landfill sites and reclaimed products can be re-used and recycled for future structures. The farmer opposite my house sold his barns within the farm yard for housing; when the contractor demolished the barns he cleaned up the bricks and reused them to make the wall all around the farmhouse thereby retaining the character of the farm.
Modern solutions and machinery permits demolition contractors to efficiently segregate waste types on or off-site. Quality items are recycled and re-used if possible in the new construction producing substantial savings in project costs in addition to being good for the planet.
Concrete can now be rapidly broken up with a giant guillotine.
Converting 6f2 gauge recycled material from the demolished buildings’ remnants provides an environmentally sustainable alternative to removing the waste to landfill and also provides and excellent sub-base for new building foundations.
Copper pipes, lead, roof tiles or slates, floor tiles, wiring and doors, and wooden panelling are valuable items that are preserved for recycling to be re-used. A lot of specialist suppliers offer up reclaimed old or classic building supplies in a lot of towns and cities.
Taller Structures
Tower blocks and chimneys are the type of tall buildings that may need to be demolished. The demolition of tall structures requires skilled approaches. The tallest building to be demolished lawfully was in 1967/8 for the Singer Building in New York. The collapse of the World Trade Centre after the 9/11 attack in late 2001 demonstrates the terrible devastation that occurs if the demolition is out of control and haphazard.
In the demolishing of high properties and sizeable structures a wrecking ball on a crane can be employed, but is seldom used because the swinging ball is relatively uncontrollable. The closeness of other property is often a deciding issue which inhibits the employment of explosives to implode a tall building. So ‘High Reach’ demolition excavators are widely-used wherever alternative methods are not possible to demolish the highest part of a tall building. Once it is down to a manageable height demolition can continue in the usual way. The various methods of demolishing tall buildings are by implosion using explosives, controlled collapse and piecemeal. To control the dust produced in demolition, water hoses and spray equipment are sometimes used and then it is called a wet demolition.
Explosions
The use of explosives in demolition is incredibly specialist work and getting it wrong could be catastrophic. If for example there is atmospheric pressure from low cloud above the implosion site, the shockwave may spread outwards rather than upwards resulting in the wave of energy and sound to break windows. If an implosion is not prepared correctly the danger may be damage to surrounding properties where flying debris might cause harm to spectators.
For many people when they think about demolition they will often have in mind the use of explosives in the dramatic collapse of a tall building. This method is actually called implosion using explosives. Implosion is essential for dense urban areas as it brings down a tall building so that the surrounding environment is damaged as little as possible. The collapse takes only seconds for the building to drop into its own footprint.
Due to the risks of working with explosives they are only used when other methods are too costly or impractical. Where there’s a partial collapse of the building and there are still primed explosives that didn’t go off, workers are in great danger because the remaining structure is highly unstable. On the other hand the demolition must continue to secure the safety of the site.
Health and Safety
The task of demolition is a much more technical and complicated process than a lot of people would appreciate. The job is very risky and requires experienced and skilled operators to undertake the task. It is crucial that personnel working in the market are thoroughly trained. Health and safety awareness is vital in demolition services so it is preferable for operatives to have gained a certificate of Competence in Demolition to ensure safety for both workers and public alike. All demolition work is regulated by Construction, Design and Management Regulations.
Commencement of the project of demolition in Nottingham can only take place after the necessary planning approval has been achieved from you presiding borough council.
Sequence of Demolition
An incorrect sequence of dismantling can lead to accidental collapse of the building as the stability of any structure is reliant on the interdependence of its component parts. Think of a house of cards and what are the results if one of many supporting cards is taken away.
There is a strict sequence of events before any demolition will take place. Councils across the country will have their particular specific list for planning approval in their area, but a typical order would be the following:-
Provision of data
Information has to be provided about the design of the structure to be demolished. Details of its previous use as well as the appropriate demolition methods to be employed, including disposal of hazardous substances, need to be submitted by the demolition company.
Survey of Demolition
A comprehensive survey of the site to recognize any structural problems, as well as risks related to hazardous or flammable substances, will need to be discussed at length with the authorities. (E.g. A disused garage where petrol was stored is often a potential fire hazard so preventative measures will need to be taken).
Preferred and Safe Method of Work
A good demolition company will be able to select the appropriate procedure for disposal showing the outline dismantling process. Planning is essential for meticulous monitoring. The authorities will require a detailed statement of the safety procedures to used, and all parties involved have to agree the techniques before any demolition can take place.
Preparation and Planning
Issues like asbestos abatement, rodent baiting, coping with hazardous substances, disconnecting utilities, and making safe any electric, gas or other services have to be shown in the planning stage. There is a great deal of preparation to be done before even starting work on demolishing the property itself.
Protection of the Public
Safety can’t be compromised so wherever there are heavily populated areas surrounding the demolition site the protection of the public is paramount. Any health risks will have to be assessed and temporary services arranged, and people affected will need to be informed.
Conclusion
The aim in demolition is to eliminate an unwanted building as safely and quickly as possible also in our modern environment efforts are made to recycle or re-use most of the old material. This is not a brand new idea even though the word itself is relatively modern. On the borders between England and Scotland after the Romans left, a sizable part of Hadrian’s Wall was hauled away and use was made of the beautifully dressed stone to construct the new buildings in the towns and villages nearby and several remain standing today.
Demolition work by its nature is an extremely hazardous business and demolishing any building is a complex and skilled process. Next time you see demolition work occurring on a building give a thought to the individuals who work in a dangerous situation daily and just how much is involved in the meticulous planning, regulations compliance, care and skill that goes on to undertaking the project to clear the path for our future.