The Different Stages of Demolition
Introduction
The definition of the phrase ‘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 UK when his work on demolishing large chimneys without the requirement of explosives was displayed on Television. Fred was an entertaining personality and became well-known as an authority on fixing tall chimneys, so when it came to knocking them down he knew the way to get it done. He would chop an alcove at the foot of the chimney, and place wooden props to hold the structure. By means of very carefully positioning the props, the chimney would collapse in the correct direction once the wood was set alight and burned away. Once he was almost crushed because he miscalculated slightly, demonstrating how hazardous demolition work really is.
The particular 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. Even though in reality the task of demolition, in some manner or other, has been occurring for thousands of years. Structures 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 left over ruins were taken away and rebuilt or used for other properties close by and must be early types of recycling.
Preserving History – Preparing the Future.
To preserve Britain’s history of agriculture the farm land between the established regions of the villages and towns is protected from development of urban sprawl. This acreage is called Green Belt and it is preserved for farming which is essential to the ongoing economy of the nation. By protecting the Green Belt, urban areas are increasingly being squeezed to produce housing, so developers need to be a lot more innovative to discover acceptable sites.
Great Britain is a nation with a very dense population per square mile. The quantity of land available for development is small in comparison to other nations. Consequently there is always a high need for space on which to build. Taking down aged and unused structures and replacing them with brand-new is an excellent method to attempt to counter this general shortage.
Land that may be disused industrial and commercial sites, but could possibly be contaminated with dangerous waste or pollution, are known as Brownfield sites. When the land has been cleaned up they are potentially valuable for redevelopment. Both Glasgow and South Wales produced gardens from old commercial sites and installed Shopping centres to attract tourists and generate income.
Greyfield sites are distinct from Brownfield sites in that they don’t have the environmental issues of toxic waste materials. The expression greyfield originates from the massive areas of asphalt that had once been car parks of commercial urban properties. Their significance is in the indisputable fact that the infrastructure like roads, electricity, water supply, sewerage, and gas is already in place. These kinds of urban areas which end up under-utilised or abandoned and so are valuable mainly because they require a small amount of remedial work to be developed. Cities such as Leeds and Manchester have experienced an enormous programme of converting the old warehouses or industrial facilities into homes, retail establishments and restaurants, retaining the main shell and renovating the interior into desirable accommodation.
The Demolition Process
Office and building demolition in Birmingham requires careful consideration to the following points.
The design type and physical dimensions of the building.
What elements have re-use value?
What will the cleaned site’s re-use be intended for?
Where are the waste by-products likely to be disposed?
What considerations 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 the building will topple; at the same time managing the manner and course of the fall. Questions of safety are extremely important, and clean-up plans will also be considered when choosing how a property will be demolished.
Traditional Demolition
At one time the standard means of demolishing a property was extremely crude. After all the services were turned off, the men and equipment would go ahead and simply just knock down the walls. Then the whole structure would collapse and the resulting debris could be piled onto trucks and be dumped in landfill sites. Concrete footings were split up by air-driven tools and the site would be cleared of rubbish ready for the new work to begin. However these days demolition activities are subject to strict planning, safety and inspection laws and are highly controlled by the local council. The way a building is constructed will mean that one section relies on another for solidity and toughness. For example the rooftop of a property isn’t fastened down other than fixing tiles with nails to avoid them sliding. The roof stays in position with its own weight as the beams are laid on the top of the walls instead of being fastened into them as they once were for much older homes. The cross beams and purlins then link the whole thing together to tie down 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 issues are taken into account in the sequence of deconstruction. In a sense, like Fred Dibnah you need to be an expert in construction to understand how to do the deconstruction.
Deconstruction and Recycling
The newest approach to demolishing properties is known as deconstruction – a green approach. Landfill sites are in short supply and so the aim when demolishing a structure is to diminish the quantity of waste material remaining.
Smaller structures such as 2 or 3 storey homes may be disassembled quite easily. The work may be a painstaking task of dismantling by hand – brick by brick – or beam by beam but by going very carefully costly resources are preserved for re-use. The additional value of deconstruction is that 90% or more of waste materials is prevented from going directly into landfill sites and reclaimed resources can be re-used and recycled for upcoming properties. The farmer opposite my family home sold his barns within the farm yard for housing; when the builder demolished the barns he cleaned up the bricks and reused them for the walls all around the farmhouse thus keeping the character of the place.
Newer specialist techniques and machinery allows demolition contractors to efficiently segregate waste material varieties on or off-site. Building resources are recycled and re-used if practical in the new building producing significant savings in project costs in addition to being good for the environment.
Concrete can now be quickly broken up with a large guillotine.
An alternative to taking the rubble from the demolition to a landfill site for dumping is to crush it on site for recycling in an environmentally friendly manner as a sub-base 6f2 material for the new building foundations.
Copper pipes, lead, roof tiles or slates, floor tiles, wiring and exterior doors, and wooden panelling are valuable items which can be rescued for recycling to be re-used. Many specialist firms offer reclaimed old or antique building materials in most towns and cities.
Taller Architectural Structures
Tower blocks and chimneys are the sort of tall buildings that might need to be demolished. The demolition of tall structures requires expert procedures. 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 assault in 2001 demonstrates the horrendous devastation that develops when the demolition is out of control and haphazard.
During the demolishing of tall properties and sizeable structures a wrecking ball on a crane may be used, but is seldom used because the swinging ball is somewhat uncontrollable. The closeness of other buildings is often a deciding issue which often prevents the employment of explosives to implode a tall building. So ‘High Reach’ demolition excavators are widely-used where alternative approaches will not be appropriate 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 extremely specialist work and getting it drastically wrong could well be catastrophic. 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 an implosion is not prepared correctly the danger may be destruction of surrounding properties where flying debris could cause injuries to spectators.
For most people when they consider demolition they might have in mind the usage of explosives in the dramatic collapse of a tall building. This process is in fact called implosion using explosives. Implosion is essential for dense cities because it brings down a tall building so the surrounding environment is damaged as little as possible. The collapse takes only mere seconds for the building to drop into its footprint.
Due to the hazards of dealing with explosives they are only 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 failed to go off, workers are in great danger because the remaining structure is highly unstable. At the same time the demolition must 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 many people would appreciate. The job is very risky and requires experienced and skilled operators to handle the task. It is essential that personnel working in the market are adequately trained. Health and safety awareness is vital in demolition services so it is best for operatives to have gained certificates of Competence in Demolition to guarantee safety for both workers and public alike. All demolition work is regulated by Construction, Design and Management Regulations.
Commencement of the project of dismantling 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 a building since the stability of any structure is reliant on the interdependence of the component parts. Think about a house of cards and what are the results if one of the supporting cards is removed.
There exists a strict sequence of events before any demolition will take place. Councils throughout the country have their own specific list for planning approval within their area, but a typical order could be the following:-
Provision of data
Information should 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 used, 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, in addition to risks related to hazardous or flammable substances, will have to be discussed in detail with the authorities. (E.g. A disused garage where petrol has been stored is a potential fire hazard so preventative measures will likely need to be taken).
Preferred and Safe Method of Work
A reputable demolition company will be able to select the appropriate method of disposal showing the outline dismantling process. Planning is essential for assiduous monitoring. The authorities will need a detailed statement of the safety procedures to used, and all parties involved have to agree the methods before any demolition will take place.
Preparation and Planning
Issues like asbestos abatement, rodent baiting, handling 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 cannot be compromised so where there are heavily populated areas around 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 goal in demolition is always to eliminate an unwanted structure as safely and quickly as possible and in our modern environment efforts are made to recycle or re-use most of the old material. This isn’t a brand new idea even though the word itself is relatively modern. On the borders between England and Scotland after the Romans left, a significant 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 a very risky business and demolishing any building is a complex and skilled process. The next time you observe demolition work occurring on a building give a thought to the individuals who work in a dangerous situation daily and how much is involved in the meticulous planning, regulations compliance, care and skill that goes on to carrying out the project to clear the path for our future.