Building Construction Technology
Demolition of Buildings
Content
What is demolition?
Demolition planning
Types of structural demolition
Methods of demolition
Demolition plan
Safety measures
Challenges in demolition
Learning Objectives
• Define demolition in construction
• Understand types and methods of
demolition
• Follow the planning and procedural steps
involved
• Recognise critical safety and environmental
precautions
• Understand the roles and responsibilities of
Quantity Surveyors
Introduction
• Demolition refers to the systematic tearing down or removal of
buildings or structures, either wholly or partially, executed
through carefully planned and managed techniques.
• The choice of demolition strategy depends on factors such as:
– the site location
– time constraints
– construction materials involved
– the intended outcome of the demolition
– the method for handling the resulting debris.
Objectives of Demolition
• Ensure the demolition is done safely and
efficiently
• Salvage as many materials as possible for
reuse or recycling
• Minimise hazards to personnel and the
public
Building Demolition Process
https://safetyculture.com/topics/building-demolition/
Building Demolition Process
https://constructioncitizen.com/blog/science-demolishing-building/1906211
https://constructioncitizen.com/blog/science-demolishing-building/1906211
Types of Demolition
Manual Demolition
Mechanical Demolition
Controlled Demolition (by Explosives)
Dismantling / Deconstruction
Progressive Demolition
https://constrofacilitator.com/different-types-of-demolition-methods-for-building-
structures/
Manual Demolition
• Labour-intensive and used for small structures
or partial demolition
• Tools: sledgehammers, crowbars, jackhammers
• Advantages: controlled, less machinery
required
• Disadvantages: slow, labour-dependent
Can you name these simple
tools?
Mechanical Demolition
• Performed using heavy machinery: excavators,
bulldozers, wrecking balls.
• Faster than manual methods.
• Used in large or medium-sized building
demolitions.
Common Types of Demolition Machines
Excavator Demolition
For smaller buildings like homes and offices, an excavator is often used to dismantle the
structure. However, buildings over 60 feet tall, as well as those made of masonry, concrete,
and steel, will require a more heavy-duty machine like a high-reach excavator. High-reach
demolition is considered a cleaner, safer way to dismantle structures, as it causes less flying
debris, dust, noise, and risk to the operator.
Wrecking Ball Demolition
• A wrecking ball is the classic icon of demolition. A massive ball of steel
(weighing 1,000 and 12,000 pounds - 450 to 5,400 kg) is suspended from a
crane and swung into a building, with its sheer weight, inertia, and gravity
doing the work to bring down a building.
• There are a few methods to release the ball. It can either be dragged back
and released, hoisted to a great height and dropped, or whipped from a
spinning crane.
Controlled Demolition (by
Explosives)
• Suitable for tall or large structures
• Requires expert planning and simulations
• Explosives are placed in structural elements to
induce collapse
Implosion Demolition
Implosion is by far the most
impressive method of
demolishing a building. However,
due to their specialised nature,
implosions are used in less than
1% of demolition works.
Implosion is the process of using
explosives to knock out a
building’s main supports,
causing the building to collapse
from the inside out.
Implosion Demolition
Implosions require the knowledge of experts called “blasters” and are often
used to demolish large structures in urban areas. A successful implosion
requires the following steps:
• Blueprint examination: Blasters study blueprints of a building to determine
which areas need to be blasted.
• Site preparation: Crews prepare a site by taking out the non-load-bearing
walls, weakening supporting columns, and wrapping columns with fencing
for a cleaner fall with less flying debris.
• Determine explosives: Blasters select an explosive based on the building’s
materials. Dynamites release shockwaves and are best used to obliterate
concrete columns. RDX can expand up to 27,000 feet per second to slice
through steel structures.
• Load explosives: The explosives are bored into columns, generally in
support columns and a few upper stories, to make it easier to break the
building into smaller pieces.
• Time detonation: Blasters first build up an electrical charge. When the
current is sent through the wire, it heats up and ignites the flammable
substance, setting off the main explosives. Blasters can time their
detonations by setting slow-burning materials to delay the explosions.
Dismantling / Deconstruction
Deconstruction and dismantling are methods of taking apart buildings to
recover reusable materials, contrasting with demolition, which focuses
on complete destruction. Deconstruction is a selective disassembly
process, while dismantling can also be part of conservation and repair
work.
• Careful removal of building components for
reuse.
• Labour- and time-intensive.
• Requires systematic disassembly of parts.
Selective Demolition
• Selective demolition is gaining popularity in today’s eco-conscious
world.
• Rather than destroying the building in one swoop, this method
involves removing specific sections of a building while retaining the
structure.
• It’s a great choice for building remodels, upgrades, and extensions,
where recycling and reusing are desired to lessen the demolition’s
environmental impact.
Selective Demolition
Similar to any kind of demolition, this method involves a thorough survey of
the building’s structure, removal of hazardous materials, and determining
potential recyclable materials. These are the steps of a selective demolition
process:
• Prepare the site: Mechanics, electricians, and plumbers cut off the
power, shut down HVAC systems, and cap open piping. Crew members
also install a temporary lighting system and add a trash chute to
maximize sorting of recyclable goods.
• Strip away nonstructural components: Labor forces dismantle the
architectural, mechanical, and electrical elements of the structure,
leaving the building’s shell.
• Remove materials and shore up building: Structure shoring and
temporary supports are added. Crews remove floor beams, load-bearing
walls, columns, and floor slabs of external sections of the building that
require demolition.
• Sort debris: The team places the deconstructed building materials into
recycle, reuse, sell, or donate bins and then begins new construction
Progressive Demolition
Progressive demolition is a controlled method of
dismantling a building by removing sections of the
structure while maintaining the stability of the
remaining parts
• Step-by-step demolition ensuring structural
integrity is maintained
• Common in urban settings
• Allows continued use of part of the structure
Planning for Demolition
• Site evaluation and risk assessment
• Environmental considerations
• Identification of structural system
• Selection of suitable demolition
method
• Preparation of demolition plan
Demolition Plan Includes
• Scope of demolition
• Sequence of operations
• Safety measures
• List of equipment
• Handling of hazardous materials
Typical
Demolition
Flowchart
Safety Measures
• Use of PPE
• Barricading the site
• Fire safety equipment
• Dust control: water spray, nets
• Emergency evacuation plan
Environmental Considerations
• Noise and dust control
• Waste minimisation
• Material recycling
• Safe disposal of hazardous waste
Waste Management
• Segregation of waste at source
• On-site and off-site recycling
• Disposal of non-recyclables
• Documentation and compliance
Sustainable Demolition
Practices
• Maximising reuse and recycling
• Energy-efficient equipment
• Green certifications and audits
• BIM for demolition planning
• Use of robotics
Challenges in Demolition
• Working in congested areas
• Asbestos and hazardous materials
• Underground utilities
• Structural uncertainties
• Noise and dust complaints
Role of QS in Demolition
Pre-Contract
• Conducting feasibility studies and preparing
cost estimates for demolition
• Assisting in the preparation of tender
documentation, including the scope of
demolition
• Advising on cost-effective demolition methods
and waste disposal strategies
Role of QS in Demolition
Post-Contract Phase
• Measurement and valuation of demolition
works in accordance with standard methods of
measurement
• Valuing salvageable materials and incorporating
credits into the final account
• Managing change orders, variations, and claims
related to unforeseen demolition challenges
Role of QS in Demolition
Sustainability and Risk Management
• Identifying and quantifying risks (e.g., asbestos, hazardous
waste) with cost implications
• Planning for sustainable demolition and material reuse
• Ensuring contractor compliance with safety and
environmental regulations
Reporting and Documentation
• Preparing interim payment certificates and final accounts
• Keeping cost records and tracking demolition progress
against the budget
• Assisting in obtaining necessary permits and statutory
approvals
Conclusion
• Demolition is an essential part of the
construction cycle
• It requires integrated planning,
coordination, and execution
• QS plays a key role in ensuring cost-
effectiveness, safety, and sustainability
