Demolition
Encyclopedia
Demolition is the tearing-down of building
s and other structure
s, the opposite of construction
. Demolition contrasts with deconstruction
, which involves taking a building apart while carefully preserving valuable elements for re-use.
For small buildings, such as house
s, that are only two or three stories high, demolition is a rather simple process. The building is pulled down either manually or mechanically using large hydraulic equipment: elevated work platforms, cranes, excavator
s or bulldozer
s. Larger buildings may require the use of a wrecking ball
, a heavy weight on a cable that is swung by a crane
into the side of the buildings. Wrecking balls are especially effective against masonry, but are less easily controlled and often less efficient than other methods. Newer methods may use rotational hydraulic shears and silenced rock-breakers attached to excavators to cut or break through wood, steel, and concrete. The use of shears is especially common when flame cutting would be dangerous.
The tallest building demolished by nonterrorist methods was the 47-story Singer Building
in New York City
, which was built in 1908 and torn down in 1967-1968 to be replaced by One Liberty Plaza
. There were later taller buildings in the area
that fell down
due to the September 11 attacks.
Before any demolition activities, there are many steps that need to take place — including but not limited to performing asbestos abatement
, removing hazardous or regulated materials, obtaining necessary permits, submitting necessary notifications, disconnecting utilities, rodent baiting, and development of site-specific safety and work plans.
The typical razing of a building is accomplished as follows:
Hydraulic excavators may be used to topple one- or two-story buildings by an undermining process. The strategy is to undermine the building while controlling the manner and direction in which it falls. The demolition project manager/supervisor will determine where undermining is necessary so that a building is pulled in the desired manner and direction. The walls are typically undermined at a building's base, but this is not always the case if the building design dictates otherwise. Safety and cleanup considerations are also taken into account in determining how the building is undermined and ultimately demolished. Hoe rams are typically used for removing the concrete road deck and piers during bridge demolition, while hydraulic shears are used to remove the bridge's structural steel
.
In some cases a crane with a wrecking ball
is used to demolish the structure down to a certain manageable height. At that point undermining takes place as described above. However crane mounted demolition balls are rarely used within demolition due to the uncontrollable nature of the swinging ball and the safety implications associated.
High reach demolition excavators are more often used for tall buildings where explosive demolition is not appropriate or possible. Excavators with shear attachments are typically used to dismantle steel structural elements. Hydraulic hammers are often used for concrete structures and concrete processing attachments are used to crush concrete to a manageable size, and to remove reinforcing steel.
To control dust, fire hoses are used to maintain a wet demolition. Hoses may be held by workers, secured in fixed location, or attached to lifts to gain elevation.
Loaders or bulldozers may also be used to demolish a building. They are typically equipped with "rakes" (thick pieces of steel that could be an I-beam or tube) that are used to ram building walls. Skid loaders and loaders will also be used to take materials out and sort steel.
The technique of Vérinage is used in France to weaken and buckle the supports of central floors promoting the collapse of the top part of a building onto the bottom resulting in a rapid, symmetrical, collapse.
The Japanese company Kajima Construction
has developed a new method of demolishing buildings which involves using computer-controlled hydraulic jacks to support the bottom floor as the support beams are removed. The floor is lowered and this process is repeated for each floor. This technique is safer and more environmentally friendly, and is useful in areas of high population density
.
Large buildings, tall chimney
s, smokestacks, and increasingly some smaller structures may be destroyed by building implosion
using explosives. Imploding a building is very fast — the collapse itself only takes seconds — and an expert can ensure that the building falls into its own footprint, so as not to damage neighboring structures. This is essential for tall structures in dense urban areas.
Any error can be disastrous, however, and some demolitions have failed, severely damaging neighboring structures. The greatest danger is from flying debris which, when improperly prepared for, can kill onlookers.
Even more dangerous is the partial failure of an attempted implosion. When a building fails to collapse completely the structure may be unstable, tilting at a dangerous angle, and filled with un-detonated but still primed explosives, making it difficult for workers to approach safely.
A third danger comes from air overpressure that occurs during the implosion. If the sky is clear, the shock wave
, a wave of energy and sound, travels upwards and disperses, but if cloud coverage is low, the shock wave can travel outwards, breaking windows or causing other damage to surrounding buildings.
Stephanie Kegley of CST Environmental described shock waves by saying, "The shock wave is like a water hose. If you put your hand in front of the water as it comes out, it fans to all sides. When cloud coverage is below 1,200 feet, it reacts like the hand in front of the hose. The wave from the shock fans out instead of up toward the sky."
While a controlled implosion is the method that the general public often thinks of when discussing demolition due to its spectacularity, it can be dangerous and is only used as a last resort when other methods are impractical or too costly. The destruction of large buildings has become increasingly common as the massive housing projects of the 1960s and 1970s are being leveled around the world. At 439 feet (133.8 m) and 2200000 square feet (204,386.7 m²), the J. L. Hudson Department Store and Addition is the tallest steel framed building and largest single structure ever imploded.
that can form deadly projectiles, and insulation that can scatter over a wide area. Non-load bearing partitions and drywall
are removed. Selected columns on floors where explosives will be set are drilled and nitroglycerin, TNT or C4 are placed in the holes. Smaller columns and walls are wrapped in detonating cord
. The goal is to use as little explosive as possible; only a few floors are rigged with explosives, so that it is safer (fewer explosives) and less costly. The areas with explosives are covered in thick geotextile
fabric and fencing to absorb flying debris. Far more time-consuming than the demolition itself is the clean-up of the site, as the debris is loaded into trucks and hauled away.
The development of plant and equipment has allowed for the easier segregation of waste types on site and the reuse within the construction of the replacement building. On site crushers allow the demolished concrete to be reused as type 1 crushed aggregate either as a piling mat for ground stabilization or as aggregate in the mixing of concrete.
Timber waste can be shredded using specialist timber shredders and composted, or used to form manufactured timber boards, such as MDF
or Chipboard
.
Safety is paramount, a site safety officer is usually assigned to each project to enforce all safety rules and regulations.
Building
In architecture, construction, engineering, real estate development and technology the word building may refer to one of the following:...
s and other structure
Structure
Structure is a fundamental, tangible or intangible notion referring to the recognition, observation, nature, and permanence of patterns and relationships of entities. This notion may itself be an object, such as a built structure, or an attribute, such as the structure of society...
s, the opposite of construction
Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
. Demolition contrasts with deconstruction
Deconstruction (building)
In the context of physical construction, deconstruction is the selective dismantlement of building components, specifically for re-use, recycling, and waste management. It differs from demolition where a site is cleared of its building by the most expedient means. Deconstruction has also been...
, which involves taking a building apart while carefully preserving valuable elements for re-use.
For small buildings, such as house
House
A house is a building or structure that has the ability to be occupied for dwelling by human beings or other creatures. The term house includes many kinds of different dwellings ranging from rudimentary huts of nomadic tribes to free standing individual structures...
s, that are only two or three stories high, demolition is a rather simple process. The building is pulled down either manually or mechanically using large hydraulic equipment: elevated work platforms, cranes, excavator
Excavator
Excavators are heavy construction equipment consisting of a boom, stick, bucket and cab on a rotating platform . The house sits atop an undercarriage with tracks or wheels. A cable-operated excavator uses winches and steel ropes to accomplish the movements. They are a natural progression from the...
s or bulldozer
Bulldozer
A bulldozer is a crawler equipped with a substantial metal plate used to push large quantities of soil, sand, rubble, etc., during construction work and typically equipped at the rear with a claw-like device to loosen densely-compacted materials.Bulldozers can be found on a wide range of sites,...
s. Larger buildings may require the use of a wrecking ball
Wrecking ball
A wrecking ball is a heavy steel ball, usually hung from a crane, that is used for demolishing large buildings. It was most common during the 1950s and 1960s. Several wrecking companies claim to have invented the wrecking ball...
, a heavy weight on a cable that is swung by a crane
Crane (machine)
A crane is a type of machine, generally equipped with a hoist, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of...
into the side of the buildings. Wrecking balls are especially effective against masonry, but are less easily controlled and often less efficient than other methods. Newer methods may use rotational hydraulic shears and silenced rock-breakers attached to excavators to cut or break through wood, steel, and concrete. The use of shears is especially common when flame cutting would be dangerous.
The tallest building demolished by nonterrorist methods was the 47-story Singer Building
Singer Building
The Singer Building or Singer Tower at Liberty Street and Broadway in Manhattan, was a 47-story office building completed in 1908 as the headquarters of the Singer Manufacturing Company. It was demolished in 1968 and is now the site of 1 Liberty Plaza....
in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
, which was built in 1908 and torn down in 1967-1968 to be replaced by One Liberty Plaza
One Liberty Plaza
One Liberty Plaza, formerly the U.S. Steel Building, is a skyscraper in lower Manhattan, New York City, at the location of the former Singer Building . 1 Liberty Plaza is currently owned and operated by Brookfield Properties. The building is tall and 54 floors. It was built in 1973...
. There were later taller buildings in the area
World Trade Center
The original World Trade Center was a complex with seven buildings featuring landmark twin towers in Lower Manhattan, New York City, United States. The complex opened on April 4, 1973, and was destroyed in 2001 during the September 11 attacks. The site is currently being rebuilt with five new...
that fell down
Collapse of the World Trade Center
The twin towers of the World Trade Center collapsed on September 11, 2001, as a result of al-Qaeda's September 11 attacks, in which terrorists affiliated with al-Qaeda hijacked four commercial passenger jet airliners, flying one into the North Tower and another into the South Tower...
due to the September 11 attacks.
Non-explosive demolition
Asbestos abatement
Many buildings contain asbestos, which was used in spray-applied flame retardant, thermal system insulation, and in a variety of other materials. Asbestos was sometimes "flocked" above false ceilings, inside technical ducts, and in many other small spaces where firefighters would have difficulty...
, removing hazardous or regulated materials, obtaining necessary permits, submitting necessary notifications, disconnecting utilities, rodent baiting, and development of site-specific safety and work plans.
The typical razing of a building is accomplished as follows:
Hydraulic excavators may be used to topple one- or two-story buildings by an undermining process. The strategy is to undermine the building while controlling the manner and direction in which it falls. The demolition project manager/supervisor will determine where undermining is necessary so that a building is pulled in the desired manner and direction. The walls are typically undermined at a building's base, but this is not always the case if the building design dictates otherwise. Safety and cleanup considerations are also taken into account in determining how the building is undermined and ultimately demolished. Hoe rams are typically used for removing the concrete road deck and piers during bridge demolition, while hydraulic shears are used to remove the bridge's structural steel
Structural steel
Structural steel is steel construction material, a profile, formed with a specific shape or cross section and certain standards of chemical composition and mechanical properties...
.
In some cases a crane with a wrecking ball
Wrecking ball
A wrecking ball is a heavy steel ball, usually hung from a crane, that is used for demolishing large buildings. It was most common during the 1950s and 1960s. Several wrecking companies claim to have invented the wrecking ball...
is used to demolish the structure down to a certain manageable height. At that point undermining takes place as described above. However crane mounted demolition balls are rarely used within demolition due to the uncontrollable nature of the swinging ball and the safety implications associated.
High reach demolition excavators are more often used for tall buildings where explosive demolition is not appropriate or possible. Excavators with shear attachments are typically used to dismantle steel structural elements. Hydraulic hammers are often used for concrete structures and concrete processing attachments are used to crush concrete to a manageable size, and to remove reinforcing steel.
To control dust, fire hoses are used to maintain a wet demolition. Hoses may be held by workers, secured in fixed location, or attached to lifts to gain elevation.
Loaders or bulldozers may also be used to demolish a building. They are typically equipped with "rakes" (thick pieces of steel that could be an I-beam or tube) that are used to ram building walls. Skid loaders and loaders will also be used to take materials out and sort steel.
The technique of Vérinage is used in France to weaken and buckle the supports of central floors promoting the collapse of the top part of a building onto the bottom resulting in a rapid, symmetrical, collapse.
The Japanese company Kajima Construction
Kajima Construction
( is a Japanese construction company. Founded in 1840, the company has its headquarters in Moto-Akasaka, Minato, Tokyo. The company is known for its DIB-200 proposal.-Demolition Technology:...
has developed a new method of demolishing buildings which involves using computer-controlled hydraulic jacks to support the bottom floor as the support beams are removed. The floor is lowered and this process is repeated for each floor. This technique is safer and more environmentally friendly, and is useful in areas of high population density
Population density
Population density is a measurement of population per unit area or unit volume. It is frequently applied to living organisms, and particularly to humans...
.
Building implosion
Chimney
A chimney is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the...
s, smokestacks, and increasingly some smaller structures may be destroyed by building implosion
Building implosion
In the controlled demolition industry, building implosion is the strategic placing of explosive material and timing of its detonation so that a structure collapses on itself in a matter of seconds, minimizing the physical damage to its immediate surroundings...
using explosives. Imploding a building is very fast — the collapse itself only takes seconds — and an expert can ensure that the building falls into its own footprint, so as not to damage neighboring structures. This is essential for tall structures in dense urban areas.
Any error can be disastrous, however, and some demolitions have failed, severely damaging neighboring structures. The greatest danger is from flying debris which, when improperly prepared for, can kill onlookers.
Even more dangerous is the partial failure of an attempted implosion. When a building fails to collapse completely the structure may be unstable, tilting at a dangerous angle, and filled with un-detonated but still primed explosives, making it difficult for workers to approach safely.
A third danger comes from air overpressure that occurs during the implosion. If the sky is clear, the shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
, a wave of energy and sound, travels upwards and disperses, but if cloud coverage is low, the shock wave can travel outwards, breaking windows or causing other damage to surrounding buildings.
Stephanie Kegley of CST Environmental described shock waves by saying, "The shock wave is like a water hose. If you put your hand in front of the water as it comes out, it fans to all sides. When cloud coverage is below 1,200 feet, it reacts like the hand in front of the hose. The wave from the shock fans out instead of up toward the sky."
While a controlled implosion is the method that the general public often thinks of when discussing demolition due to its spectacularity, it can be dangerous and is only used as a last resort when other methods are impractical or too costly. The destruction of large buildings has become increasingly common as the massive housing projects of the 1960s and 1970s are being leveled around the world. At 439 feet (133.8 m) and 2200000 square feet (204,386.7 m²), the J. L. Hudson Department Store and Addition is the tallest steel framed building and largest single structure ever imploded.
Preparation
It takes several weeks or months to prepare a building for implosion. All items of value, such as copper wiring, are stripped from a building. Some materials must be removed, such as glassGlass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
that can form deadly projectiles, and insulation that can scatter over a wide area. Non-load bearing partitions and drywall
Drywall
Drywall, also known as plasterboard, wallboard or gypsum board is a panel made of gypsum plaster pressed between two thick sheets of paper...
are removed. Selected columns on floors where explosives will be set are drilled and nitroglycerin, TNT or C4 are placed in the holes. Smaller columns and walls are wrapped in detonating cord
Detonating cord
Detonating cord is a thin, flexible plastic tube filled with PETN . With the PETN exploding at a rate of approximately 4 miles per second, any common length of det cord appears to explode instantaneously...
. The goal is to use as little explosive as possible; only a few floors are rigged with explosives, so that it is safer (fewer explosives) and less costly. The areas with explosives are covered in thick geotextile
Geotextile
Geotextiles are permeable fabrics which, when used in association with soil, have the ability to separate, filter, reinforce, protect, or drain...
fabric and fencing to absorb flying debris. Far more time-consuming than the demolition itself is the clean-up of the site, as the debris is loaded into trucks and hauled away.
Deconstruction
A new approach to demolition is the deconstruction of a building with the goal of minimizing the amount of materials going to landfills. This "green" approach is applied by removing the materials by type material and segregating them for reuse or recycling. With proper planning this approach has resulted in landfill diversion rates that exceed 90% of an entire building and its contents in some cases.The development of plant and equipment has allowed for the easier segregation of waste types on site and the reuse within the construction of the replacement building. On site crushers allow the demolished concrete to be reused as type 1 crushed aggregate either as a piling mat for ground stabilization or as aggregate in the mixing of concrete.
Timber waste can be shredded using specialist timber shredders and composted, or used to form manufactured timber boards, such as MDF
Medium-density fibreboard
Medium-density fiberboard is an engineered wood product formed by breaking down hardwood or softwood residuals into wood fibres, often in a defibrator, combining it with wax and a resin binder, and forming panels by applying high temperature and pressure...
or Chipboard
Particle board
Particle board, or particleboard , is an engineered wood product manufactured from wood particles, such as wood chips, sawmill shavings, or even saw dust, and a synthetic resin or other suitable binder, which is pressed and extruded...
.
Safety is paramount, a site safety officer is usually assigned to each project to enforce all safety rules and regulations.
See also
- Construction waste
- Demolition wasteDemolition wasteDemolition waste is waste debris from destruction of a building. The debris varies from insulation, electrical wiring, rebar, wood, concrete, and bricks. It also may contain lead, asbestos or different hazardous materials....
- Collapse of the World Trade CenterCollapse of the World Trade CenterThe twin towers of the World Trade Center collapsed on September 11, 2001, as a result of al-Qaeda's September 11 attacks, in which terrorists affiliated with al-Qaeda hijacked four commercial passenger jet airliners, flying one into the North Tower and another into the South Tower...
, which involved an unusual method of causing structural failureStructural failureStructural failure refers to loss of the load-carrying capacity of a component or member within a structure or of the structure itself. Structural failure is initiated when the material is stressed to its strength limit, thus causing fracture or excessive deformations... - World Trade Center controlled demolition conspiracy theories
- House demolitionHouse demolitionHouse demolition is primarily a military tactic which has been used in many conflicts for a variety of purposes. It has been employed as a scorched earth tactic to deprive an advancing enemy of food and shelter, or to wreck an enemy's economy and infrastructure. It has also been used for purposes...
(military tactic) - Excavator Ram guardRam guardRam Guards protect the hydraulic ram on an excavator which is used to move the boom and other parts of the arm of an excavator to carry out work....
(Protection of excavators used for demolition) - Demolition beltDemolition beltIn military terminology, a demolition belt is a selected land area sown with explosive charges, mines, and other available obstacles to deny use of the land to enemy operations, and as a protection to friendly troops.There are two types of demolition belt:...
- ICE demolition protocolICE demolition protocolThe ICE Demolition Protocol was produced by EnviroCentre, in partnership with London Remade, for the Institution of Civil Engineers . Launched at the ICE in November 2003, it has subsequently been referenced in planning guidance in both England and Scotland, at both national and local...
- National Federation of Demolition ContractorsNational Federation of Demolition ContractorsThe National Federation of Demolition Contractors is a United Kingdom construction trade association representing companies involved in demolition work.The NFDC represents its sector as one of four representative bodies on the UK Contractors Group....
(UK)