Introduction

The definition of the word ‘demolish’ is deliberate and controlled collapse of a structure. In the late 1970’s Fred Dibnah became the most famous steeplejack in Britain when his work on demolishing tall chimneys without the need for explosives was shown on Television. Fred was an authority on repairing tall chimneys, so when it came to taking them down he knew just how to do it. He would cut an alcove at the base of the chimney, and then place wooden props to support the structure. By carefully positioning the props, the chimney would collapse in the right direction when the wood was set alight and burned away. Once he was nearly crushed when he miscalculated demonstrating how dangerous demolition work is.

The actual word to demolish only came into being in 1570, and was used after that to mean the deliberate taking down or destroying of a building or structure. Although in fact the process of demolition in some form or other has been occurring for thousands of years. Buildings have been destroyed either by natural disturbances of the Earth’s crust or during battles or attacks on villages for as long as there have been structures. The remaining ruins would be removed and rebuilt or used for other buildings nearby and must be the first examples of recycling.

Preserving the past - preparing the future.

To preserve Britain’s history of agriculture the land between built up areas of the villages and towns is protected from development of urban sprawl. This land is known as Green Belt and is preserved for farming which is vital to the continuing economy of the country. By containing the Green Belt, urban areas are squeezed to provide housing, so developers have to be more creative to find suitable sites.

Britain is a country with a very dense population per square mile. The amount of land available for construction is limited compared to other countries. Therefore there is always a high demand for space on which to build. Taking down old and unused buildings and replacing them with new is one way to counteract this shortage.

Land that may be disused industrial and commercial sites, but could be contaminated with hazardous waste or pollution, are called Brownfield sites. Once the land has been cleaned up they are potentially valuable for redevelopment. Both Glasgow and South Wales created gardens out of old industrial sites and put in Shopping centres to attract visitors.

Greyfield sites are distinct from Brownfield sites in that they do not have the environmental concerns of toxic waste. The term greyfield comes from the large areas of asphalt which had once been car parks of commercial urban properties. Their value is in the fact that the infrastructure such as roads, electricity, water, sewage, and gas is already in place. These urban areas are underutilised or abandoned and are valuable because require very little remedial work to be developed. Cities such as Leeds and Manchester have had a massive programme of converting the old warehouses or factories into apartments, shops and restaurants, retaining the original shell and refurbishing the interior into desirable accommodation.

The Demolition process

A professional demolition contractor always makes an assessment of the following basic items.

• The construction and size of the building.
• What items are valuable for re-use?
• How will the old site be re-used?
• How is the waste to be disposed of?
• Electricity water, sewage and gas mains.

Hydraulic excavators and bulldozers can be used to undermine the walls at the base, so that the structure will topple; at the same time controlling the manner and direction of the fall. Safety issues are paramount, and clean-up strategies are also taken into account when determining how the building will be demolished.

Traditional Demolition

Once all the services were disconnected, the men and machinery would go in and just knock down the walls. The whole structure would collapse and the resulting debris would be piled onto lorries and disposed of in landfill sites. Concrete foundation would be broken up by pneumatic drills and the site would be cleared of rubbish. However today demolition practices are subject to strict planning, safety and monitoring regulations and are highly controlled by the local authority.

Deconstruction and Recycling

The new approach to demolishing buildings is known as deconstruction - a green approach. Landfill sites are in short supply so the aim when demolishing a building is to minimise the amount of waste remaining.

Small structures such as two or three storey houses can be dismantled quite easily. The work may be a painstaking task of dismantling by hand - brick by brick - or beam by beam but by going carefully costly materials are preserved for re-use. The value of deconstruction is that 90% or more of waste is saved from going into landfill sites and reclaimed materials can be re-used and recycled for future buildings. The farmer opposite my house sold his barns in the farm yard for housing; when the builder demolished the barns he cleaned up the bricks and reused them for the wall around the farmhouse thus retaining the character of the farm.

Modern techniques and machinery allows demolition companies to efficiently segregate waste types on or off-site. Construction materials are recycled and re-used whenever possible in the new structure making considerable savings in project costs as well as being good for the environment.

Concrete can now be rapidly broken up with a new machine called a guillotine.By creating 6f2 recycled material out of the demolished building the demolition company can avoid the expense of hauling the building waste to landfill.

Copper pipes, lead, roof tiles or slates, floor tiles, wiring and doors, and wood panelling are valuable artifacts that are saved for recycling and re-use. Many specialist firms sell reclaimed old or antique building items in most towns and cities.

Tall Buildings

Tower blocks and chimneys are the type of tall buildings that may need to be demolished. The demolition of tall buildings necessitates expert techniques. The tallest building to be demolished lawfully was in 1967/8 of the Singer Building in New York. The collapse of the World Trade Centre after the 9/11 attack in 2001 illustrates the terrible devastation that occurs if the demolition is uncontrolled and haphazard.

In the demolishing of tall buildings and large structures a wrecking ball on a crane can be used, but is rarely practiced because the swinging ball is rather uncontrollable. The proximity of other buildings is a determining factor which prevents the use of explosives to implode a tall structure. So ‘High Reach’ demolition excavators are used where other methods are not suitable to demolish the top 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 very specialist work and getting it wrong would be catastrophic. If for instance there is atmospheric pressure from low cloud above the implosion site, the shockwave may spread outwards instead of upwards causing the wave of energy and sound to break windows. If an implosion is not prepared correctly the danger may be damage to surrounding buildings where flying debris may cause injury to spectators.

For many people when they think about demolition they may have in mind the use of explosives in the dramatic collapse of a tall building. This process 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.

Because of the risks of working with explosives they will only be used when other methods are too costly or impractical. Where there is 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 has to continue to secure the safety of the site.

Health and Safety

The work of demolition is a much more technical and complicated process than most people would appreciate. The job is highly dangerous and requires experienced and skilled operators to carry out the work. It is essential that personnel working in the industry are thoroughly trained. Health and safety awareness is crucial in demolition services so it is advisable 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 the Construction, Design and Management Regulations.

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 its component parts. Think of a house of cards and what happens if one of the supporting cards is removed.

There is a strict sequence of events before any demolition can take place. Councils throughout the country will have their own specific list for planning approval in their area, but a typical order would be as follows:-

• Provision of Information
Information must be provided about the construction of the structure to be demolished. Details of its previous use and 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, as well as risks associated with hazardous or flammable substances, will need 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 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 require a detailed statement of the safety procedures to used, and all parties involved need to agree the methods before any demolition can take place.

• Preparation and Planning
Issues such as asbestos abatement, rodent baiting, dealing 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 lot 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 hazards will need to be assessed and temporary services arranged, and people disturbed will have to be informed.

A Nottingham demolition project, or project in almost any town council district will require a similar process to be adhered to in order to approve permission for demolition.

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 most of the old material. This is not a new idea although 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 some are still standing today.

Demolition work by its nature is a very 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 people 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 way for our future.

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Introduction

Taking down old buildings and replacing them with new is a process that has been going on for thousands of years. The destruction of buildings might have occurred during battles or attacks on villages; or due to natural disturbances such as earthquakes or volcanic activity. The resultant ruins would need to be removed and rebuilt. So the idea of demolition would have come about where a population wished to re-inhabit a specific area or site. (One famous example is the Holy Temple in Jerusalem which was deliberately destroyed by the Assyrians around 586 BCE. After 50 years of occupation the Jews returned to Jerusalem and began the re-construction of the second temple which took seventy years to complete.)

However the actual word to demolish only came into being in 1570, and was used from then on to mean the deliberate taking down or destroying of a building or structure.

Preserving the past - preparing the future.

In a country like Britain with very dense populations per square mile, there is a limited amount of land available for construction. The land between built up areas of the villages and towns is known as Green Belt and is protected from development to preserve the agricultural and natural heritage which is vital to the economy of the country.

The outcome of this policy is that there is a constant shortage of land for housing and industry, so the developers have to be more creative when providing structures for the population. One of the ways of doing this is to find places where the buildings are no longer commercially viable or have been abandoned, and re-use the area for different purposes. These areas are known as brownfield, or greyfield sites. In some cities, particularly Leeds and Manchester, the old warehouses or factories have been converted into apartments, retaining the original shell and reconfiguring the internal dimensions into modern living accommodation.

Brownfield sites are disused industrial and commercial facilities where the land may be contaminated with hazardous waste or pollution. They are potentially valuable for significant redevelopment once they have been cleaned up. Greyfield sites are urban properties that have been underutilised or abandoned, but do not have the environmental issues of brownfield sites. They were termed greyfield sites because of large areas of asphalt that covered the land. These sites are valuable because they already have the infrastructure such as water, sewage, electricity and gas in place and do not need remedial work to develop the site.

When a structure is to be removed there are different ways of approaching the task. The size and construction of the building, the new use of the site and whether there are valuable elements suitable for re-use, will all determine how it is to be demolished.

Traditional Demolition

Traditionally, once all the services were disconnected, the machinery and men would go in and just knock down the walls which caused the roof to collapse and then drag all the debris away. Any concrete hard standing would be broken up ready for removal. The site would be cleared of rubbish and disposed of in landfill sites. However modern demolition practices are very controlled and are subject to strict planning, safety and monitoring regulations.

Small structures such as two or three storey houses can be dismantled quite easily with hydraulic excavators and bulldozers using an undermining process. The walls are undermined at the base, in order to topple the structure; at the same time the manner and direction of the fall is controlled. Clean-up and safety issues are also taken into account when choosing how the building will be undermined and demolished.

Larger buildings such as tower blocks and chimneys require more specialist techniques, and are outlined below.

Deconstruction

A new approach to demolishing buildings is deconstruction - a green approach. The aim is to minimise the amount of waste going to landfill sites by carefully preserving valuable materials for reuse. The work may be a painstaking task of dismantling by hand - brick by brick - or beam by beam. The reclaimed materials are then recycled or re-used for future buildings. The results of deconstruction can save in excess of 90% waste from going to a landfill site. When the farmer opposite to my house sold his farm yard with barns for housing, the builder demolished the barns, cleaned up the bricks and reused them for the perimeter wall of the farmhouse. At the time I was looking for some rubble as a base for a path and the builder let me take several barrow loads off his pile.

Recycling

Historically when old buildings were ruined from disuse or war damage the local people would gradually remove the stone and use it to build their new structures such as houses or barns. Hadrian’s wall between Carlisle and Newcastle has mostly disappeared because after the Romans left, the local population made off with the beautifully dressed stone the Roman craftsmen had used in the building of the wall. So even in those days people understood the value of recycling because it was much cheaper than having to quarry and dress the stone themselves.

At one time the rubble resulting from a demolished building would be taken to a landfill site for disposal. Now however concrete can be rapidly broken up with the latest machine called a guillotine and the resultant rubble can be crushed and used as sub-base material for the foundation of the new building which is to replace the old, or sent to other construction sites. These days this crushed rubble is called 6f2 crushed stone or 6f2 crushed material.

Modern machinery and techniques allows the demolition companies to efficiently segregate waste types on or off-site. Wherever possible construction materials are recycled and re-used in the new structure. Recycling of waste contributes to a considerable savings in project costs and is good for the environment.

When we renovated our bungalow 20 years ago the builder, who was a bell ringer, found an old beam from a bell tower that was being renovated, and after carefully treating it, installed it in the kitchen. It gave the room some badly needed character and has never needed any further treatment.

Copper pipes, wiring, roof tiles or slates, floor tiles and doors, and wood panelling are some of the valuable items that are saved for recycling and re-use. There are specialist yards in many towns where reclaimed old or antique artefacts are available for purchase.

Tall Buildings 

The demolition of tall buildings requires skilled techniques. In some cases a wrecking ball on a crane may be used to demolish the top part of a tall building until it is down to a manageable height. However this process is rarely used due to the uncontrollable factor of the swinging ball and the proximity of other buildings.

Other methods of demolition of tall buildings are by implosion using explosives, controlled collapse and piecemeal. Also ‘High Reach’ demolition excavators are used where explosives are not appropriate. Once the building is down to a more manageable height demolition continues in the usual way. 

The steeplejack Fred Dibnah became famous in the late 1970’s for his work on demolishing tall chimneys without the need for explosives. He would cut an ingress at the base of the chimney, use wooden props to support the brickwork and then burn the props so that the chimney toppled hopefully in the right direction.

The tallest building to be lawfully demolished was the Singer Building of New York in 1967/8. More recently the collapse of the World Trade Centre after the 9/11 attack in 2001 shows the terrible devastation that could occur if the demolition is not controlled and very carefully contained.

In the demolishing of tall buildings and large structures water hoses and spray equipment is used to control the dust and would is termed a wet demolition.

Explosions 

What comes to mind for many people when they think about demolition would be the dramatic collapse of a tall building using explosives. However it is usually the process of implosion, using explosives, that brings down a tall building so that it does as little damage as possible to the surrounding environment. Implosion is essential for dense urban areas and is very fast, the collapse taking only seconds, with the building dropping inwards into its own footprint.

Using explosives is specialist work and is a very skilled process and getting it wrong can be disastrous. If an implosion is not prepared correctly the danger may be damage to neighbouring structures or even killing onlookers from flying debris. Even more dangerous is a partial collapse of a building where the remaining structure is unstable and there are still primed explosives that failed to go off. Workers are in great danger if or when continuing the demolition.

Other risks of working with explosives occurs when the atmospheric pressure from low cloud above the implosion site will cause the shockwave to spread outwards instead of upwards. The wave of energy and sound created will break windows and cause other damage to the surrounding buildings.

Because of the dangers of working with explosives, implosion will only be used when other methods are too costly or impractical.

Health and Safety

Demolition of any building is highly dangerous and is a much more complicated and technical process than most people would realise. Experienced and skilled operators are essential to ensure safety for both workers and public alike. The stability of any structure is reliant on the interdependence of its component parts, so an incorrect sequence of dismantling could result in an unplanned collapse.

Health and safety is paramount in demolition work so personnel working in the industry have to be adequately trained. It is advisable for operatives to have gained a Certificate of Competence in Demolition to ensure they have the necessary skills and safety awareness. All demolition work is regulated by the Construction, Design and Management Regulations.

Sequence of Demolition

There has to be a sequence of actions before any demolition can take place. Each area council will have their own specific list for planning approval, but a typical order would be as follows:-

• Provision of Information
  The demolition company must provide information about the construction to be demolished, its previous use and the appropriate demolition method to be applied including disposal of hazardous substances.
• Survey of Demolition
  Identification of any structural problems as well as risks associated with hazardous or flammable substances will require a thorough survey of the site. (E.g. Where petrol has been stored, ie disused garage, precautions need to be taken to prevent a fire hazard).
• Preferred and Safe Method of Work
  A reputable company involved in demolition will be able to select the appropriate method of disposal. Planning and outlining the dismantling process is necessary for meticulous monitoring. A detailed statement outlining the safety process needs to be agreed by all parties involved before any demolition can take place.
• Preparation and Planning
  There is a lot of preparation to be done before starting work on demolishing the building itself. Issues such as asbestos abatement, disconnecting utilities, rodent baiting, dealing with hazardous substances and making safe any electric, gas or other services have to be resolved.
• Protection of the Public
  Where demolition is carried out in heavily populated areas the protection of the public is paramount. Safety cannot be compromised. Temporary services may need to be arranged, health hazards assessed and people affected will need to be informed.

Conclusion

The word ‘demolish’ is interpreted as the deliberate and controlled collapse of a structure. Demolition work is a very risky business and demolishing any building is a complex and skilled process. The aim in demolition is to remove an unwanted building as safely and quickly as possible, recycle or re-use most of the old material, and clear the site ready for the subsequent use.

In the centre of Nottingham over the last few years there has been a major reconstruction of what was an old car park into a brand new shopping development. While this was going on the public were only really aware of the boarding around the area, a change in traffic direction and maybe some big lorries going in and out of the site.

So the next time you see structures being demolished to make way for the new, give a thought to the company involved who’s team are daily working in a dangerous environment, adhering to all of the regulations and carefully and meticulously carrying out the project to bring us the modern conveniences we have come to expect and clearing the way for the future.