This document provides information on demolition and dismantling work. It discusses what demolition is, the planning process, types of structural demolition including progressive demolition, deliberate collapse mechanisms, and deliberate removal of elements. It also outlines various demolition methods like manual demolition, demolition by machines using a top-down approach, hydraulic crushers with long boom arms, wrecking balls, implosions, and other techniques. Finally, it lists important precautions that should be taken before and during demolition work for safety.

1. Demolition And
Dismantling Work

2. Content
What is Demolition?
Planning
Types of structural demolition
Methods Of Demolition
Precautions Before and During Demolition
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3. What is Demolition?
• Demolition means dismantling, razing, destroying or
wrecking any building or structure or any part thereof by
pre-planned and controlled methods.
• Demolition methods can vary depending on the area where
it will be held on, time available, the building material, the
purpose of the demolition and the way that debris is going
to be disposed.
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4. Planning
• Before beginning the actual work of demolition a structure,
a careful study shall be made of the structure which is to be
pulled down and also of all its surroundings.
• Definite plan of procedure for the demolition work,
depending upon the manner in which the loads of the
various structural parts are supported, shall be prepared and
approved by the engineer-in-charge and this shall be
followed as closely as possible, in actual execution of the
demolition work.
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5. 1.
• Building Appraisal and Demolition
Plan
2.
• Utilities
3.
• Hazardous Material
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6. 1.Building Appraisal and Demolition Plan
• The study of the structure, before demolition, shall
be carried out by means of surveys which shall
include a General Survey and a Structural Survey,
with photographs or videos taken for future
reference.
• The demolition plan must also be accompanied by a
report together with structural calculations assessing
the stability of the building to be demolished and all
affected buildings, structures, streets, land and
services. 6

7. 2.Utilities
• The common utilities encountered in building demolition
generally include Electricity, Water, Gas,
Telecommunication, Drainage and its accessories, and
Overhead and Underground Cables.
• The demolition plan shall ensure that during the course of
demolition, no existing utilities in the vicinity of the
demolition sites are affected by the demolition operation.
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8. 3.Hazardous Material
• If hazardous materials, such as asbestos containing
materials, petroleum contamination and radioactive
contamination, exist in the building, further investigation
and removal of such hazardous material or contamination
by specialist shall be considered.
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9. Types of structural demolition
1.
• Progressive demolition
2.
• Deliberate collapse mechanisms
3.
• Deliberate removal of elements
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10. 1.Progressive demolition
• Progressive demolition is the controlled removal of sections
of the structure, whilst retaining the stability of the
remainder and avoiding collapse of the whole or part of the
building to be demolished.
• Where progressive demolition is adopted, it is essential that
the key structural members on which the integrity of the
structure relies should, together with their sequence of
removal, be clearly indicated in the method statement and
also on site.
• Progressive demolition should be considered for the
majority of sites and is particularly useful in confined and
restricted areas.
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11. 2.Deliberate collapse mechanisms
• Demolition by deliberate collapse is the removal of key
structural members to cause complete collapse of the whole
or part of the building or structure.
• Where deliberate collapse demolition is adopted, the key
structural members to be removed should be clearly
indicated, together with the sequence of removal, in the
method statement and also on site.
• This method should be employed only on detached,
isolated, reasonably level sites where the whole structure is
to be demolished.
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12. 3.Deliberate removal of elements
• The deliberate removal of elements should be considered to
be the removal of selected parts of the structure by
dismantling or deconstruction.
• The elements to be removed should be identified and the
effects of removal on the remaining structure fully
understood and included in the method statement, with the
elements to be removed marked on site.
• Sections of the structure should not be removed if instability
of any of the remainder could result in a possible risk to
personnel on the site and to other people nearby.
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13. Methods Of Demolition
• There are multiple types of demolition procedures used to
take down structures.
• The choice of demolition method depends on the project
conditions, site constraints, and sensitivity of the
neighborhood and availability of equipment.
• The choice of technique should enable the re-use and/or the
recycling of materials arising from the demolition.
Irrespective of which demolition method is adopted, its
choice should be based on minimizing the risk to personnel.
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14. Demolition Methods
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15. Manual Method
• Manual methods are carried out top down, proceeding, in
general, from the roof to ground.
• The particular sequence of demolition may vary, depending
on site conditions and structural elements to be demolished.
• For reinforced concrete buildings, jack hammers are
commonly used to break down the concrete.
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16. • Oxy-acetylene torch could be used to cut the
reinforcements.
• The reinforcements shall remain until all the
concrete connecting to or supported by the
reinforcement is broken away or when its support is
no longer required.
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17. Fig: Demolition By Manual Method
Source:www.konkret.info.pl
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18. Demolition Sequence for Manual Method
•Demolition sequence shall be determined according to
actual site conditions, restraints, the building layout, the
structural layout and its construction. In general, the
following sequence shall apply:
•All cantilevered structures, canopies, verandahs and
features attached to the external walls shall first be
demolished prior to demolition of main building and its
internal structures on each floor.
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19. – When demolishing the roof structure, all lift machine rooms and
water tanks at high level shall be demolished in “top down”
sequence to the main roof level.
– Demolition of the floor slabs shall begin at mid span and work
towards the supporting beams.
– Floor beams shall be demolished in the order of cantilevered
beams, secondary beams and then main beams.
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20. – Non-load bearing walls shall be removed prior to demolition of
load bearing walls.
– Columns and load bearing walls shall be demolished after
removal of beams on top end.
– If site conditions permit, the first floor slab directly above the
ground floor may be demolished by machine standing on
ground.
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21. Top Down — By Machines
• The sequence of demolition by machine is typically the
same as the top down manual method, except that most of
the demolition is done by mechanical plant.
• The demolition begins with the lifting of the mechanical
plant on to the building top floor.
• When rope or tie wire is used for pulling, the workers shall
be protected or stay away from the area within reach of the
rope or tie wire.
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22. Demolition sequence For Top Down-By Machines
• Prior to demolition of internal floors, all cantilevered slabs
and beams, canopies, and verandahs shall first be
demolished.
• The structural elements, in general, shall be demolished in
the sequence of slab, secondary beams and then main
beams.
• Mechanical plant shall descend from the floors with
temporary access ramp, or be lowered to the next floor by
lifting machinery or by other appropriate means.
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23. • When a mechanical plant has just descended from the floor
above, the slabs and beams, in two consecutive floors may
be demolished by the mechanical plant simultaneously. The
mechanical plant may work on structural elements on the
same floor and breaking up the slabs on the floor above.
• The beams and columns shall be demolished by gradually
breaking down the concrete or by pulling them down in a
controlled manner.
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24. Typical sequence of demolition by top down method with
Machines
1.Demolish slab &
beam
2.Continue demolishing
slab & beam
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25. 3.Access ramp to lower
floor
4.Demolition of interior
column
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26. 5.Cut external wall &
column
6.Pull down wall
section
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27. Hydraulic Crusher with Long Boom Arm
• The crusher attachment breaks the concrete and the
reinforcement by the hydraulic thrust through the long
boom arm system.
• The hydraulic crusher can be operated from the ground
outside the building.
• This method is also suitable for dangerous buildings, silos
and other industrial facilities.
• For environmental reason, it should be used wherever
practicable because of its quietness.
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28. Fig: Hydraulic Crusher with Long Boom Arm
Source: www.jewellattachments.com
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29. Wrecking Ball
• The wrecking ball application consists of a crane
equipped with a steel ball.
• The destruction of the building is by the impact
energy of the steel ball suspended from the crawler
crane.
• The wrecking ball operates outside the building.
• This method is suitable for dilapidated buildings,
silos and other industrial facilities.
• However, the operation requires substantial clear
space. 29

30. Fig: Wrecking Ball Method
Source: www.flickr.com
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31. Implosion
• 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.
• The technique weakens or removes critical supports so that
the building can no longer withstand the force of gravity
and falls under its own weight.
• The explosives are just the trigger for the demolition. It's
gravity that brings the building down.
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32. • Explosives are loaded and progressively detonated on
several different levels of the building so that the building
structure falls down on itself at multiple points.
• When everything is planned and executed correctly, the total
damage of the explosives and falling building material is
sufficient to collapse the structure entirely, so cleanup crews
are left with only a pile of rubble.
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33. • For buildings with a steel support structure, blasters
typically use the specialized explosive material
cyclotrimethyle netri nitramine, called RDX for short.
• RDX-based explosive compounds expand at a very high
rate of speed, 8,230 meters per second.
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34. Fig: Demolition By Implosion
Source:www.911-strike.com
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35. Other Methods
• Non Explosive Demolition Agent
– Non Explosive Demolition Agent (NEDA) is a static demolition
agent. When the reaction takes place in a confined drill hole, the
NEDA generates an expansive pressure to crack and break
concrete and stone.
– The NEDA is a suitable application in a restrictive environment
where noise, flying debris and vibration are less tolerated.
– NEDA may be used on foundation works, pile caps or structures
that are fully supported.
– When used in rock, NEDA should be contained within strong,
flexible, impermeable bags to prevent uncontrolled entry into rock
joints.
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36. • Thermal Lance
• Cutting of reinforced concrete by thermal lance involves very high
temperature up to 2,000 - 4,000°C. The extremely high heat requires
special precautionary measures and care. The use of a thermal lance in
cutting reinforced concrete shall not be used unless:
– The project demonstrated that there is no other viable
alternative;
– Adequate protective measures are provided to isolate the
operation and to prevent any potential fire spreading out; and
– Adequate protective measures are provided to prevent the injury
of the workers, and any third party by flame and the molten
concrete.
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37. Fig: Thermal Lance
Source: www.krl.com.au/
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38. Precautions Before and During Demolition
• Precautions before and during demolition shall be as
follows:
– The demolition shall not be commenced until precautionary
measures have been inspected and approved. It is advisable to
inform adjoining neighbors prior to the demolition so that they
may close windows or take other measures.
– Before demolition is commenced and also during the progress of
such work, all electric cables or apparatus which are liable to be a
source of danger, other than a cable or apparatus used for the
demolition works shall be disconnected.
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39. – During the progress of demolition, the work shall be under the
continuous supervision of the demolisher or ofan experienced
foreman.
– Unless otherwise expressly approved, demolition shall be executed
storey by storey commencing at the roof and working downward.
– All practicable precautions shall be taken to avoid danger from
collapse of a building when any part of a framed or partly framed
building is removed.
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40. –When the demolition site adjoins a street or public walkway, a 2.4
meter high solid hoarding shall be erected on the street boundary unless
the building is setback at least twice its height from the street boundary,
in which case a security fence having a minimum height of 1.5 meters
may be utilized.
–Notices lettered displaying the words “WARNING DEMOLITION IN
PROGRESS” to be fixed to the hoarding or security fence.
–Dust creating material, unless thoroughly dampened shall not be thrown
or dropped from the building but shall be lowered by hoisting apparatus
or removed by material chutes.
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41. – No wall, chimney or other structure or part of a structure shall be
left unattended or unsupported in such a condition that it may
collapse due to wind or vibration or otherwise become dangerous.
– Protective outriggers shall be installed where necessary to guard
against danger to life or property or when required by the Building
Surveyor.
– No bulk excavation or levelling of the site forms part of this
demolition permit.
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