Introduction
The definition of the word ‘demolish’ is deliberate and controlled collapse of a structure. During the late 1970’s Fred Dibnah took over as the most popular steeplejack in The United Kingdom when his work on demolishing large chimneys without the requirement of explosives was displayed on Television. Fred was an intriguing character and became renowned as an expert on repairing tall chimneys, so when it came to knocking them down he knew precisely how to do it. He would chop an alcove at the base of the chimney, and then place wooden props to underpin the structure. As a result of carefully placing the props, the chimney would fall in the correct place when the wood was set alight and burned away. On one occasion he was nearly killed because he miscalculated somewhat, demonstrating just how dangerous demolition work really is.
The actual word to demolish only came to exist in 1570, and was adopted after that to mean the deliberate taking down or destroying of a building or structure. Though in reality the task of demolition, in some form or other, has been occurring for millenia. Buildings have been completely wrecked either by natural disturbances of the Earth’s crust or during battles or assaults on towns for as long as there have been buildings. The remaining ruins were taken away and rebuilt or used by other structures close by and must be early types of recycling.
Preserving the Past – Preparing the Future.
To preserve Britain’s tradition of agriculture the land between the established regions 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 fundamental to the continuing financial state of the nation. By protecting the Green Belt, urban areas are now being squeezed to supply housing, so developers must be a lot more creative to uncover suitable sites.
Britain is a country with an incredibly dense human population per square mile. The quantity of land for building is restricted compared to other countries. Consequently there’s always a high demand for space on which to build. Taking down outdated and unused structures and replacing them with new is another way to attempt to counter this general shortage.
Land that may be disused industrial and commercial sites, but might be contaminated with harmful waste or pollution, are classified as Brownfield sites. Once the land has been cleaned up they can be potentially valuable for redevelopment. Both Glasgow and South Wales created gardens using old commercial sites and installed Shopping centres to draw in visitors and generate income.
Greyfield sites are distinct from Brownfield sites because they do not possess the environmental issues of harmful waste material. The expression greyfield comes from the large areas of asphalt which had once been car parks of industrial urban units. Their value is incorporated in the indisputable fact that the infrastructure which includes roads, electricity, water supply, sewerage, and gas is already available. These urban areas which come to be under-utilised or abandoned and therefore are important because they require little or no remedial work to be renovated. Cities including Leeds and Manchester have had a huge programme of changing the old warehouses or industrial facilities into flats, retail establishments and cafes, retaining the original shell and refurbishing the interior into desirable accommodation.
The Demolition Process
A skilled building demolition company contracted to do the work will have taken the time to perform an initial basic review of the following.
The construction type and actual dimensions of the structure.
What products have re-use value?
What will the cleared site’s re-use be intended for?
Where are the waste material by-products going to be disposed?
What steps need to be made with regards electricity, water, sewerage and gas mains.
Hydraulic excavators and bulldozers may be used to undermine the walls at the roots, so that the structure will topple; at the same time managing the manner and course of the fall. Issues of safety are paramount, and clean-up tactics are also taken into consideration when choosing the way the building is going to be demolished.
Traditional Demolition
At one time the traditional way of demolishing a building was quite crude. Once the services were disconnected, the men and equipment would expect to go ahead and simply knock down the walls. Then the whole building would fall and the resulting debris would be piled on lorries and be dumped in landfill sites. Concrete foundations would be split up by pneumatic drills and then the site could be cleaned of rubbish ready for the new work to commence. Having said that these days demolition practices are at the mercy of rigorous planning, safety and monitoring polices and are also hugely governed by the local council. How a building is constructed means that one section depends on another for solidity and strength. For instance the roof of a property isn’t fastened down save for fixing tiles with nails to prevent them slipping. The roof stays in place with its own weight as the beams are laid on top of the walls instead of being attached into them like they once were for much older houses. The cross beams and purlins then tie the entire thing together to tie down the frame of the roof. To this slats are laid to provide a frame for laying on the tiles or slates. Some other sections of a building may also be interdependent so in terms of demolition these concerns are considered in the sequence of deconstruction. In a sense, like Fred Dibnah you have to be an expert in construction to understand how to carry out the deconstruction.
Deconstruction and Recycling
The new system of demolishing properties is known as deconstruction – an environmentally friendly approach. Landfill sites are in limited supply and so the aim when demolishing a property is to diminish the amount of waste material remaining.
Modest constructions like two or three storey buildings can be taken apart quite simply. The project may be a slow task of dismantling by hand – brick by brick – or beam by beam but by going carefully expensive materials are preserved for re-use. The beauty of deconstruction is that 90% or more of waste materials is rescued from going directly into landfill sites and reclaimed products can be re-used and recycled for upcoming structures. The farmer opposite my new home sold his barns within the farm yard for construction; when the contractor demolished the barns he cleaned up the bricks and reused them to make the walls around the farmhouse thereby retaining the character of the farm.
Newer solutions and equipment allows demolition companies to successfully segregate waste varieties on or off-site. Quality materials are recycled and re-used whenever possible within the new structure creating substantial reductions in project costs as well as being good for the planet.
Concrete can now be rapidly cracked with a large guillotine.
Crushing of the demolished building and stone to 6f2 aggregate is an environmentally friendly option to disposal of the rubble in a landfill site.
Copper pipes, lead, roof tiles or slates, floor tiles, wiring and doors, and wooden panelling are useful objects which might be preserved for recycling to be re-used. Countless specialist firms provide reclaimed old or vintage building items in the majority of towns and cities.
Tall Structures
Tower blocks and chimneys are the type of tall buildings that may need to be demolished. The demolition of tall architectural structures necessitates specialist techniques. The tallest structure 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 assault in 2001 demonstrates the terrible devastation that occurs when the demolition is uncontrolled and haphazard.
During the demolishing of high properties and larger structures a wrecking ball on a crane may be used, but is hardly ever practiced as the swinging ball is relatively uncontrollable. The proximity of other structures is often a deciding issue that inhibits the use of explosives to implode a tall building. So ‘High Reach’ demolition excavators are widely-used where other methods will not be possible to demolish the highest section 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
Using explosives in demolition is very specialist work and getting it drastically wrong could be disastrous. If for instance there is atmospheric pressure from low cloud above the implosion site, the shockwave may spread outwards as opposed to upwards resulting in the wave of energy and sound to break glass windows. If the implosion is not prepared correctly the risk might be destruction of surrounding buildings where flying debris could cause injury to spectators.
For many individuals when they think of demolition they may have in mind the employment of explosives in the spectacular collapse of a tall building. This method is actually called implosion using explosives. Implosion is essential for dense cities since 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 footprint.
Due to the hazards of dealing with explosives they will only be used when other methods are too costly or impractical. Where there’s a partial collapse of a building and there are still primed explosives that didn’t go off, workers will be in great danger since the remaining structure is highly unstable. At the same time the demolition needs to continue to secure the safety of the site.
Health and Safety
The work of demolition is an infinitely more technical and complicated process than most people would appreciate. The job is extremely hazardous and requires experienced and skilled operators to carry out the job. It is vital that personnel working in the industry are appropriately trained. Health and safety awareness is crucial 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 way of the Construction, Design and Management Regulations.
Before the demolition of a building in Nottingham project starts make sure your demolition contractor has used a similar process to gain demolition planning approval.
Sequence of Demolition
An incorrect sequence of dismantling will result in unplanned collapse of a building since the stability of any structure is reliant on the interdependence of the component parts. Think of a house of cards and what are the results if one of the supporting cards is taken away.
There exists a strict sequence of events before any demolition can take place. Councils throughout the country have their particular specific list for planning approval inside their area, but a typical order could be :-
Provision of data
Information has to be provided about the construction 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, have to be submitted by the demolition company.
Survey of Demolition
A thorough survey of the site to identify any structural problems, along with risks associated with hazardous or flammable substances, will have to be discussed in detail with the authorities. (E.g. A disused garage where petrol was stored is a potential fire hazard so preventative measures will have to be taken).
Preferred and Safe Method of Work
A professional demolition company will be able to select the right technique for disposal showing the outline dismantling process. Planning is essential for assiduous monitoring. The authorities will demand an in depth 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 such as 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 structure itself.
Protection of the Public
Safety can’t be compromised so where you can find heavily populated areas surrounding the demolition site the protection of the public is paramount. Any health hazards will need to be assessed and temporary services arranged, and individuals affected will have to be informed.
Conclusion
The aim in demolition is always to eliminate an unwanted structure 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 may not be a new idea even though the word itself is relatively modern. On the borders between England and Scotland after the Romans left, a large 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. The next time you observe demolition work occurring on a building offer a thought to the individuals who work in a dangerous situation daily and just how much is associated with the meticulous planning, regulations compliance, care and skill that goes on to carrying out the project to clear the way for our future.