Introduction
The meaning of the phrase ‘demolish’ is deliberate and controlled collapse of a structure. During the late 1970’s Fred Dibnah became the most renowned steeplejack in The British Isles when his work on demolishing high chimneys without the requirement of explosives was displayed on Tv. Fred was an interesting character and became renowned as a specialist on repairing tall chimneys, so when it came to taking them down he knew just how to do it. He normally would cut an alcove at the foot of the chimney, then place wooden props to underpin the structure. By very carefully setting the props, the chimney would be likely to fall in the correct place once the wood was set alight and burned away. On one occasion he was very nearly crushed because he miscalculated slightly, showing just how hazardous demolition work truly is.
The actual term to demolish only came into being in 1570, and was adopted from then on to mean the deliberate taking down or destroying of a building or structure. Although in reality the job of demolition, in some form or other, has been taking place for 1000’s of years. Buildings have been demolished either by natural disruptions of the Planet’s crust or in the course of battles or attacks on communities for as long as there have been structures. The leftover wrecks were taken away and rebuilt or used by other buildings in the area and must be early examples of recycling.
Preserving History – Preparing the Future.
To preserve The UK’s tradition of farming the farm land between the established areas of the villages and towns is shielded from expansion of urban sprawl. This land is recognized as Green Belt and it is preserved for farming which is fundamental to the ongoing economic system of the nation. By protecting the Green Belt, urban areas are now being squeezed to provide housing, so developers must be a lot more resourceful to locate acceptable sites.
Britain is a country with an extremely dense human population per square mile. The quantity of land available for development is restricted in comparison to other countries. Therefore there’s always a high need for space on which to build. Taking down outdated and abandoned structures and replacing them with brand-new is one way to attempt to counter this general shortage.
Land which may be disused industrial and commercial sites, but may be polluted with harmful waste or pollution, are classified as Brownfield sites. When the land has been cleaned up they may be potentially valuable for redevelopment. Both Glasgow and South Wales produced gardens from old commercial sites and installed Shopping centres to draw in tourists and generate income.
Greyfield sites are completely different to Brownfield sites in that they do not have the environmental problems of toxic waste material. The term greyfield arises from the large areas of asphalt which often had once been car parks of industrial urban buildings. Their significance is incorporated in the fact that the infrastructure which includes roads, electricity, water supply, sewerage, and gas is already in place. These urban areas which come to be under-utilised or abandoned and so are valuable due to the fact they require a small amount of remedial work to be developed. Cities including Leeds and Manchester have had a huge programme of converting the old warehouses or factories into apartments, shops and cafes, retaining the main shell and renovating the interior into desirable accommodation.
The Demolition Process
When a building requires demolition there are certain facts need to be taken into consideration.
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 by-products likely 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 bottom, so that the building will topple; at the same time controlling the manner and course of the fall. Safety issues are paramount, and clean-up tactics are usually taken into account when determining the way the structure is to be demolished.
Traditional Demolition
In the old days the standard way of demolishing a building was incredibly crude. As soon as the services were shut off, the men and equipment would probably go ahead and just knock down the walls. Then the whole building would collapse and the ensuing debris could be piled on trucks and be dumped in land fill sites. Concrete footings would be broken up by pneumatically-driven drills and then the site could be cleared of waste ready for the new work to start. Then again nowadays demolition practitioners are at the mercy of strict planning, safety and monitoring regulations and are also hugely governed by the local council. The way in which a building is constructed means that one area is dependent on another for stability and toughness. For example the rooftop of a property isn’t fastened down save for fixing roof tiles with nails to prevent them slipping. The roof stays in position using its own weight because the beams are laid on top of the walls instead of being fixed into them like they once were for much older homes. The cross beams and purlins then connect the whole 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 in terms of demolition these concerns are taken into account in the sequence of deconstruction. In this way, like Fred Dibnah you need to be a professional in construction to understand how to carry out the deconstruction.
Deconstruction and Recycling
The newest approach to demolishing structures is called deconstruction – a green approach. Landfill sites are in short supply therefore the aim when demolishing a building is to diminish the quantity of waste leftover.
Smaller constructions like two or three storey homes can be taken apart relatively easily. The project can be a slow task of dismantling by hand – brick by brick – or beam by beam but by proceeding with care costly components are preserved for re-use. The additional value of deconstruction is that 90% or maybe more of waste material is prevented from going into landfill sites and reclaimed products can be re-used and recycled for upcoming buildings. The farmer opposite my new home sold his barns in the farm yard for construction; when the contractor demolished the barns he cleaned up the bricks and reused them for the wall all around the farmhouse thereby keeping the character of the farm.
Contemporary techniques and machinery enables demolition companies to efficiently segregate waste material groups on or off-site. Building products are recycled and re-used when possible within the new structure producing substantial savings in project costs as well as being good for the planet.
Concrete can now be easily broken up using a large guillotine.
Rather than rubble belonging to the demolished building being taken to a landfill site for disposal it can be crushed on site to become 6f2 sub-base material or 6f2 crushed material, for the foundations of the new building, or it can be sold on and transported to other sites.
Copper pipes, lead, roof tiles or slates, floor tiles, wiring and doors, and wooden panelling are valued objects that are saved for recycling to be re-used. Many specialist businesses offer up reclaimed old or classic building materials in a lot of towns and cities.
Taller Buildings
Tower blocks and chimneys are the kind of tall structures that may need to be demolished. The demolition of tall structures necessitates expert tactics. The highest 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 attack in 2001 demonstrates the horrendous devastation that is caused if the demolition is out of control and haphazard.
During the demolishing of tall buildings and large structures a wrecking ball on a crane may be used, but is seldom attempted because the swinging ball is relatively uncontrollable. The closeness of other buildings is a deciding factor which often forbids the use of explosives to implode a tall building. So ‘High Reach’ demolition excavators are used where other approaches will not be suitable to demolish the highest portion 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 incredibly specialist work and getting it drastically wrong would be devastating. If for example there exists 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 the implosion isn’t prepared correctly the risk might be destruction of surrounding buildings where flying debris might cause harm to spectators.
For most people when they think about demolition they might have in mind the employment of explosives in the dramatic collapse of a tall building. This method is in fact called implosion using explosives. Implosion is essential for dense cities as it brings down a tall building so that the surrounding environment is damaged as little as possible. The collapse takes only mere seconds for the building to drop into its own footprint.
Because of the risks of dealing with explosives they will only be 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 failed to go off, workers will be in great danger because the remaining structure is very unstable. On top of that the demolition has to carry on and secure the safety of the site.
Health and Safety
The task of demolition is an infinitely more technical and complicated process than a lot of people would appreciate. The work is highly dangerous and requires experienced and skilled operators to carry out the work. It is crucial that personnel working in the industry are adequately trained. Health and safety awareness is necessary in demolition services so it is best for operatives to have gained a certificate of Competence in Demolition to ensure safety for both workers and public alike. All demolition jobs are regulated by the Construction, Design and Management Regulations.
Your local Nottingham demolition company has the necessary skills to ensure that they complete the procedure above in order to gain demolition planning approval.
Sequence of Demolition
An incorrect sequence of dismantling will result in unplanned collapse of a building because 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 many supporting cards is taken away.
There is a strict sequence of events before any demolition will take place. Councils all over the country will have their particular specific list for planning approval inside their area, but a typical order would be :-
Provision of information
Information should be provided about the construction of the structure to be demolished. Details of its previous use and the appropriate demolition methods to be employed, including disposal of hazardous substances, need to be submitted by the demolition company.
Survey of Demolition
A thorough survey of the site to spot any structural problems, along with risks related to hazardous or flammable substances, should be discussed at length with the authorities. (E.g. A disused garage where petrol has been stored is 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 correct procedure for disposal showing the outline dismantling process. Planning is essential for vigilant monitoring. The authorities will need an in depth statement of the safety procedures to used, and all parties involved must 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 need to be shown in the planning stage. There is a lot 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 hazards will need to be assessed and temporary services arranged, and people disturbed will have to be informed.
Conclusion
The aim in demolition is to eliminate an unwanted house as safely and quickly as possible and in our modern environment efforts are made to recycle or re-use a lot of the old material. This isn’t a new idea even though the word itself is relatively modern. On the borders between England and Scotland after the Romans left, a sizable portion 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 are still standing today.
Demolition work by its nature is an extremely risky business and demolishing any building is a complex and skilled process. 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 involved in the meticulous planning, regulations compliance, care and skill that goes on to undertaking the project to clear the way for our future.