Critical Sequences in Demolition
Introduction
The definition of the word ‘demolish’ is deliberate and controlled collapse of a structure. During the late 1970’s Fred Dibnah became the most renowned steeplejack in Great briBain when his work on demolishing tall chimneys without having the need for explosives was displayed on Tv. Fred was an interesting character and became renowned as an expert on repairing tall chimneys, so when it came to taking them down he knew just how to acheive it. He would chop an niche at the base of the chimney, then place wooden props to hold the structure. As a result of very carefully 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 very nearly killed because he miscalculated slightly, showing how hazardous demolition work really is.
The actual 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 job of demolition, in some mode or other, has been occurring for thousands of years. Buildings have been demolished either by natural disturbances of the Planet’s crust or in the course of battles or attacks on towns for as long as there have been structures. The remaining wrecks were taken away and rebuilt or used by other buildings in the area and must be early types of recycling.
Preserving History – Preparing the Future.
To preserve The UK’s tradition of agriculture the land between the established parts of the villages and towns is protected from expansion of urban sprawl. This land is known as Green Belt and it is preserved for farming that is fundamental to the continuing financial state of the country. By protecting the Green Belt, urban areas are increasingly being squeezed to supply housing, so developers need to be a lot more creative to uncover acceptable sites.
Great Britain is a country with an extremely dense human population per square mile. The quantity of land for development is restricted in comparison with other nations. Therefore there is always a healthy demand for space on which to build. Taking down old and unused buildings and replacing them with new is one method to combat this shortage.
Land that is disused industrial and commercial sites, but could possibly be contaminated with hazardous waste or pollution, are called Brownfield sites. When the land has been cleaned up they’re potentially valuable for redevelopment. Both Glasgow and South Wales constructed gardens using disused commercial sites and installed Shopping centres to attract visitors and generate income.
Greyfield sites are totally different to Brownfield sites because they do not possess the environmental issues of dangerous waste. The expression greyfield comes from the massive areas of asphalt which had once been car parks of commercial urban properties. Their advantage is in the fact that the facilities such as roads, electricity, water, sewerage, and gas is already available. These urban areas which end up under-utilised or abandoned and therefore are precious simply because they require little or no remedial work to be renovated. Cities like Leeds and Manchester have experienced an enormous programme of converting the old warehouses or industrial facilities into flats, retail establishments and cafes, retaining the original shell and refurbishing the interior into modern accommodation.
The Demolition Process
When a building requires demolition there are certain facts need to be taken into consideration.
• The design type and actual dimensions of the structure.
• What elements have re-use value?
• What will the cleared site’s re-use be 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 are often used to weaken the walls at the bottom, so the structure will topple; at the same time controlling the manner and path of the fall. Safety issues are extremely important, and clean-up systems are also taken into account when determining how the structure is to be demolished.
Traditional Demolition
In the past the traditional manner of demolishing a property was incredibly primitive. After the services were turned off, the men and machinery would go in and simply just knock down the walls. Then the entire framework would collapse and then the resulting debris would be stacked on trucks and be dumped in land fill sites. Concrete footings would be split up by pneumatically-driven drills and the site could be cleared of waste ready for the new work to start. Having said that today demolition activities are at the mercy of rigid planning, health and safety and inspection regulations and are also hugely governed by the local authority. How a building is constructed means that one section is dependent on another for solidity and sturdiness. For instance the rooftop of a house isn’t fastened down apart from fixing tiles with nails to avoid them sliding. The roof stays in position with its own weight as the beams are laid on top of the walls as opposed to being fastened into them as they once were for much older homes. The cross beams and purlins then connect 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. Some 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 do the deconstruction.
Deconstruction and Recycling
The new method of demolishing structures is known as deconstruction – a green approach. Landfill sites are in limited supply therefore the aim when demolishing a structure is to diminish the amount of waste leftover.
Small constructions for instance 2 or 3 storey buildings may be disassembled quite simply. The work may be a slow task of dismantling manually – brick by brick – or beam by beam but by going carefully costly materials are safeguarded for re-use. The additional value of deconstruction is that 90% or maybe more of waste material is rescued from going directly into landfill sites and reclaimed resources can be re-used and recycled for future buildings. The farmer opposite my family home sold his barns in the farm yard for housing; when the builder demolished the barns he cleaned up the bricks and reused them to make the wall around the farmhouse hence retaining the character of the place.
Newer techniques and machinery permits demolition contractors to effectively segregate waste material varieties on or off-site. Quality products are recycled and re-used whenever possible within the new building producing substantial savings in project costs in addition to being good for the planet.
Concrete can now be quickly split up using a giant guillotine.
Through the use the new crushing plant machinery the demolished building bricks and stone can be recycled into 6f2 recycled materials for use on new buildings. Crushed material from the demolition can be used as a sub-base for the new building foundations or used on other sites where construction is underway.
Copper pipes, lead, roof tiles or slates, floor tiles, wiring and doors, and wood panelling are valued artifacts which can be preserved for recycling to be re-used. A lot of specialist businesses offer up reclaimed old or vintage building materials in the majority of towns and cities.
Taller Buildings
Tower blocks and chimneys are the sort of tall buildings which may need to be demolished. The demolition of tall architectural structures requires skilled tactics. The highest structure to be demolished lawfully was in 1967/8 for the Singer Building in New York. The fall of the World Trade Centre after the 9/11 assault in late 2001 demonstrates the horrible devastation that occurs when the demolition is out of control and haphazard.
In the demolishing of tall buildings and large structures a wrecking ball on a crane can be used, but is rarely attempted since the swinging ball is somewhat uncontrollable. The closeness of other property is a deciding factor that forbids the employment of explosives to implode a tall building. So ‘High Reach’ demolition excavators are widely-used where other techniques will not be possible 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 extremely specialist work and getting it drastically wrong could be disastrous. If for example there is atmospheric pressure from low cloud above the implosion site, the shockwave may spread outwards instead of 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 properties where flying debris could cause injury to spectators.
For many individuals when they think of demolition they might have in mind the employment of explosives in the dramatic collapse of a tall building. This process is in fact called implosion using explosives. Implosion is vital for dense cities because 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 fall into its footprint.
Because of the risks of dealing 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 top of that the demolition needs 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 many people would appreciate. The job is highly hazardous and requires experienced and skilled operators to handle the work. It is vital that personnel working in the market are adequately trained. Health and safety awareness is important in demolition services so a good idea is 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 way of 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 can lead to unplanned collapse of a building as the stability of any structure is reliant on the interdependence of its component parts. Consider a house of cards and what are the results if one of the supporting cards is taken away.
There is a strict sequence of events before any demolition can take place. Councils throughout the country have their particular specific list for planning approval in their area, but a typical order would be as follows:-
• Provision of information
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, need to be submitted by the demolition company.
• Survey of Demolition
A comprehensive survey of the site to identify any structural problems, along with risks regarding hazardous or flammable substances, should be discussed in detail with the authorities. (E.g. A disused garage where petrol has been stored is often a potential fire hazard so preventative measures will have to be taken).
• Preferred and Safe Method of Work
A good demolition company will be able to select the suitable method of disposal showing the outline dismantling process. Planning is essential for assiduous monitoring. The authorities will require a detailed statement of the safety procedures to used, and all parties involved must agree the techniques before any demolition will 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 must be shown in the planning stage. There is a great deal of preparation to be done before even starting work on demolishing the building 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 risks will need to be assessed and temporary services arranged, and individuals affected must be informed.
Conclusion
The aim in demolition is to eliminate an unwanted building as safely and quickly as possible and in our modern environment efforts are made to recycle or re-use the majority of the old material. This may not be 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 are still standing today.
Demolition work by its nature is an extremely dangerous 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 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.
