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Before any demolition activities, there are many steps that need to take place  including but not limited to performing asbestos abatement, 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. 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 
A wrecking ball in action at the demolition of the Rockwell Gardens. 
A high-reach excavator is used to demolish this tower block. Large buildings, tall chimneys, 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 (134 m) and 2,200,000 square feet (204,000 m), the J. L. Hudson Department Store and Addition is the tallest steel framed building and largest single structure ever imploded 
Demolition of a chimney at the former brewery "Henninger" in Frankfurt am Main, Germany, on 2 December 2006 
From Wikipedia, the free encyclopedia : Demolition of buildings |
