1. BET2492/BPS3413 CONSTRUCTION SAFETY
Lecture 8 : Demolition works

2. LEARNING OUTCOMES
Upon completion of the class, it is expected that student will be able to:
LO1: Identify hazards on demolition works
LO2: Determine suitable controls when performing demolition works

3. INTRODUCTION
Demolition is one of the most hazardous construction operations - responsible for more deaths and major injuries than any other activity
If a demolition project is well planned the risks of injury and death can be minimized
The planning and execution of a demolition project should only be done by appropriately competent persons
The work should be supervised by someone with sufficient knowledge of the particular structure being dismantled
Expert advice from structural engineers will be necessary

4. Demolition in progress

5. PRINCIPAL HAZARDS OF DEMOLITION WORK
noise and vibration from heavy plant and equipment
falls from height or on the same level
falling debris
electric shock
premature collapse of the structure being demolished
fires and explosions from the use of flammable and explosive substances
dust and fumes
smoke from burning waste timber
the silting up of drainage systems by dust
pneumatic drills and power tools
the problems arising from spilt fuel oils
the existence of services, such as electricity, gas and water
manual handling
collision with heavy plant
presence of asbestos and other hazardous substances
plant and vehicles overturning

6. PRE-DEMOLITION INVESTIGATION & SURVEY
The owner of a property is required to provide the demolition contractor with a pre-demolition investigation and survey
A full site investigation must be made by a competent person – determine the hazards and associated risks which may affect the demolition workers and the public
Competent person - a specialist structural engineer who will also advise on the temporary support of adjacent buildings and the correct method of dismantling or demolition

7. ASPECTS UNDER INVESTIGATION
The construction details of the structures or buildings to be demolished (including the materials used, fragile roofs, rot, the presence of cantilevered structures and any general weaknesses)
The location of any underground or overhead services (water, electricity, gas and sewage)
The location of any underground cellars, storage tanks, chimneys, balconies or bunkers particularly if flammable or explosive substances were previously stored
Neighboring structures or buildings
The previous use of the premises
The means of access to the site
The load carrying capacity of adjoining land including
The removal of waste
The presence of underground culverts
The details of any traffic or pedestrian routes through the site
The need for possible temporary support structures for the building being demolished and adjoining buildings
The provision of welfare facilities
Falls of materials and people
The proximity of neighbors
The location of any dangerous machinery
The location of any public thoroughfares adjacent to the structure or building
The presence of asbestos, lead or other hazardous or radioactive substances and any associated health risks
The name of the planning supervisor.
Environmental issues, such as dust, water pollution and noise
Public safety including the provision of high fencing or hoardings
Manual handling issues

8. PRE-DEMOLITION INVESTIGATION & SURVEY
Details of the construction structure of building to be demolished would include whether it was built of brick, pre-stressed concrete, reinforced concrete or steel
Important to consult with legal advisers to ensure that there are no legal covenants or disputes which could affect operations on the site
The planning supervisor must notify the Health and Safety Executive of the proposed demolition work- a written risk assessment of the structure to be demolished

9. PRE-DEMOLITION INVESTIGATION & SURVEY
The site manager should arrange for suitable plant and equipment to be provided so that the work can be executed to the standards required by health and safety legislation
Issues of public protection, local traffic management and possible road closures – avoid by notifying the local authority
The provision of temporary access roads, welfare facilities, office accommodation, fuel storage and plant maintenance facilities on site - considered at the planning stage.

10. ENVIRONMENTAL MONITORING
Environmental monitoring may need to be carried out in certain situations
Some of the most common hazardous substances in demolition work include:
lead – is most dangerous when it is in the air as a fume or dust (e.g. cutting steelwork coated with lead-based paint or dismantling of tanks containing lead-based petrol)
asbestos – where possible it should be removed before any other demolition work starts and must always be removed by a licensed contractor. Asbestos may be found in sprayed coatings, thermal and acoustic insulation materials, fire resistant walls/partitions, asbestos cement sheets or flooring materials
PCBs – a toxic substance found in electric transformers and capacitors, refrigeration and heating equipment
silica – occurs in stone, some bricks and concrete aggregate. Any demolition of structures constructed from these materials will give rise to dust containing silica.

11. ENVIRONMENTAL MONITORING
Residues of hazardous substances may also create a hazard to demolition workers
Storage tanks, vessels, pipes and other confined spaces may contain flammable vapours or toxic sludges – formerly used in industrial or chemical processes

12. DEMOLITION METHOD STATEMENT
There are two forms of demolition:
piecemeal – where the demolition is done using hand and mechanical tools such as pneumatic drills, cranes and demolition balls, hydraulic pusher arms or heavy duty grabs
deliberate controlled collapse – where explosives are used to demolish the structure. This technique should only be used by trained, specialist competent persons. This is the most economic form of demolition but it is the most hazardous and everyone must be at a safe distance at the time of the collapse
A risk assessment should be made by the contractor undertaking the demolition
This risk assessment will be used to draw up a method statement for inclusion in the health and safety plan.

13. DEMOLITION METHOD STATEMENT
Content of method statement:
details of the method of demolition to be used - the means of preventing premature collapse or the collapse of adjacent buildings, and the safe removal of debris from upper levels to prevent overloading due to the debris
details of site access and security
details of the location of any underground or overhead services
details of protection from falling materials arrangements
details of equipment, including access equipment, required and any hazardous substances to be used
arrangements for the protection of the public and the construction workforce against noise and whether hazardous substances, such as asbestos or other dust, are likely to be released
details of the isolation methods for any services which may have been supplied to the site and any temporary services required on the site

14. PRIOR TO DEMOLITION..
The isolation of all services (gas, electricity and water) which feed the site is essential before any demolition takes place
Proper arrangements must be made with a reputable waste disposal contractor for the disposal of demolition waste
The site should be made secure with relevant signs posted to warn members of the public of the dangers
Asbestos containing material requires special care and will only be dismantled by a licensed contractor
A safe system of work is developed for demolition which ensures that people are distanced as far as possible from the demolition area.
Glass must be removed from all windows before demolition starts

15. CONSTRUCTION PHASE HEALTH & SAFETY PLAN
Should include the following:
the co-ordination of and provision of information to other contractors
risk assessments and other statutory assessments
emergency procedures
health and safety monitoring arrangements
site rules
welfare arrangements
the provision of information and training to the workforce
consultation arrangements with the workforce.

16. DEMOLITION USING EXPLOSIVES
An exclusion zone must be established at a distance from and surrounding the structure to be demolished
An exclusion zone comprises four areas:
1. the plan area of the structure to be demolished
2. the designed drop area where the bulk of the structure is designed to drop
3. the predicted debris area which is beyond the design drop area and where the rest of the debris is predicted to drop
4. the buffer area between the predicted debris area and the boundary of the exclusion zone.

17. MANAGEMENT OF THE DEMOLITION AND GENERAL CONTROLS
Demolition hazard control involves implementing measures which reduce the risk at the demolition site
Elimination is the most effective control measure. This involves removing the hazard or hazardous work practice from the site, by the following actions:
disconnecting services to the demolition site
ensuring there are no sparks or ignition sources, where a risk of fire or explosion exists
ensuring separation between the public and demolition activities
excluding unauthorized persons from the site

18. MANAGEMENT OF THE DEMOLITION AND GENERAL CONTROLS
Substituting or replacing a hazard or hazardous work practice with a less hazardous one could include the following:
using a controlled collapse technique, in place of people working at heights
using power shears in place of grinding or oxyacetylene cutting, where a risk of fire exists
Isolating or separating the hazard or hazardous work practice from workers and others involved in the demolition area by the following:
installing screens on plant to protect from dust and noise
installing barriers and fences
marking off hazardous areas

19. SPECIFIC ISSUES IN DEMOLITION WORKS
Premature collapse - one of the main causes of serious injury resulting from demolition work due to ineffective planning
Protection from falls and falling material
Noise
Dust
Siting and use of machinery – applicable to competent person only
Environment – contamination needs to be identified
Competence and training