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Identify a derelict building and taking into account factors such as its previous use, condition, structural features and location, prepare a plan for the safe demolition of the building that identifies the preferred method of demolitionand outlines suitable technical and procedural control measures.
The objectives of this report are to identify a derelictbuilding and plan its demolition. The planning has to take account of thespecificities of the building's structure, its previous use, the site, theneighbouring properties and other parameters. Control measures from a healthand safety point of view has to be included.
The building identified is a very old Victorian three-storeybuilding that has not been used for many years.
The methodology consists of analysing the existing structureand adjoining properties. A detailed description of the structure has beengiven and the demolition sequence has been chosen in accordance with thestructure and in a way to cause minimal disruption to other properties and thegeneral public.
The actual demolition plan is given in the form of a list oftasks and a brief explanation for each task. The demolition process has beendivided into critical phases.
The control measures have been incorporated in the plan ofthe demolition but a health and safety risk assessment has been done that liststhe possible hazards from such a work.
1 The Derelict Building
1.1 Structures to beDemolished
This three storey Victorian building is one of threebuildings in the same compound that used to house an old hospital on the site.The other two are also not in use and there are plans to demolish them as wellbut at a later date. The Victorian building is a detached three storey buildingpositioned centrally on the site with a shed used as boiler house on one side.Access is from the south side where the building is about 10 m from the road.
The Boiler House is set to the north of the building but is detachedfrom the main building. It consists of one tall stone building with attachedoil and water tanks.
There is a network of underground pipes between the boilerhouse and the Victorian buildings for the supply of hot water for domestic andheating purposes.
As most Victorian buildings of that size, these buildingshave certain characteristics that distinguish them from other buildings. Thebuilding construction is of masonry. The load bearing walls are made of twolines of brick with no gap in between. These external walls rise undisrupted tothe roof.
The roof consists of square timber rafters sitting on atimber ring beam on top of the walls. The rafters support a series ifrectangular timber purlins that in turn support the slate tiles that form theroof. The edges are sealed by hammered lead foils.
The internal floors are made up of timber joists supportedby stone brackets off the brick walls. A grid of timber beams are supported offthe joists and wooden planks are nailed to the top of the timber beams. Thepartition walls consist of plastered timber frames.
The buildings also consist of basement that have been sealedseveral years ago but has not been filled.
There is no insulation on the walls and roof and there is noair conditioning installed in the building. The only services are the hot andcold water pipes, drainage pipes and electric wiring. The water pipes date fromthe original construction and are of lead. The sanitary drainage pipes alsodate from original and consist of 5 cast iron pipes and fittings lined withbitumen. The electric wiring has been installed much later and has been fixedto the timber joists by means of nailed clips.
The boiler house is a stone building with corrugated ironsheet roof. It contains a coal-fired boiler that is out of operation. Theboiler is connected to the Victorian buildings via underground pipes to supplyhot water. The Boiler House also contains a large number of pipe work andfittings as well as a coal pit.
1.2 AdjacentLand Use
The site is situated between two main roads on the South andEast sides and two B-class roads on the North and West sides. The site shares aboundary with a much newer construction used as NHS clinic which will remain inuse during the demolition. The site is surrounded completely with 2.5 m tallmasonry walls except on the south side. The south side is cordoned by wroughtiron fencing. There is no wall between the parking lot of the clinic and thecompound.
Ground investigations were carried out on samples of thesouth of the site during the construction of some of the newer buildings. Theinvestigation results are available from the council. Since no new constructionis being undertaken in this project, ground information is deemed to beunnecessary.
2 Description of Works
Since the building has not been in use for a significantperiod of time, its exact state is not known even to the client. So the firstthing to be done is a full structural survey of the building to assess thedanger from hazardous material and to decide on the best method of carrying outthe work. This will need to be done as early as the tender stage as theinformation from this survey will be essential for the rest of the work.
Before the start of the demolition, a full scale demolitionsurvey will need to be done. This should take account of the following(Holroyd, 1999):
- Adjoining properties
- The type of structure and the key elements in it.
- The condition of the elements.
- Any requirement for temporary works or staging during demolition.
- Are there any confined spaces.
- Are there hazards from asbestos, lead, contaminated land, etc?
- Is access and egress adequate?
2.1.2 Preferred Method
The demolition can be carried in a number of ways but giventhe proximity of other properties such as the NHS block and main roads, thedemolition should be carried out in a way as to minimise disruption to theneighbourhood and also to cause minimum noise level.
The demolition should be planned to be carried out in acontrolled manner from top to bottom, de-constructing the components in thereveres order of original construction. Demolition balls will be used only asthe last resort and no explosive will be used.
2.1.3 Method Statement
A method statement needs to be prepared before the jobstarts and should cover (Holroyd, 1999):
- The sequence and method of demolition noting access/egress details.
- Pre-weakening details of the structure
- Personnel safety, including the general public
- Service removal/make safe
- Services to be provided
- Flammable problems
- Hazardous substances
- The use of transport and waste removal
- Identity of people with control responsibilities.
3 Particulars of Work
3.1 Phase1: Planning
Before the demolition starts, careful planning is requiredto ensure smooth operations. It also allows problems to be identified at an earlystage. The cost of remedial action at the planning stage is significantly lessthan that at the demolition stage. So, allocation of time and effort to carefuland thorough planning is very important.
3.2 Phase2: Site Preparation
Once on site, the demolition cannot start immediately. Thereis a lot of work that needs to be done to make the demolition work possible.Several preventive measures and control measures have to be established right atthe start. It is cheaper and better than to apply remedial action when thingsgo wrong. The planning stage must have identified the areas that need attentionand the control measures that are required. The processes involved in theactual demolition are site specific and site preparations must be doneaccordingly. Good site preparation also allows minimal disruption to theneighbourhood.
3.3 Phase3: Demolition of Boiler House
From the risk assessment, it is clear that the boiler house,although much smaller in size that the main building, represents a greaterhealth hazard to the site workers as it contains asbestos, oil tanks, watertanks and a lot of pipe work. To reduce the exposure of the personnel to suchrisks, it has been decided to demolish and make safe the boiler house firstbefore starting with the main building.
3.4 Phase4: Demolition of Main Building
The main building will be demolished manually as far aspossible. In order to contain the noise and air pollution as much as possible,the external walls and roof will be maintained until the entire interior hasbeen demolished. The internal partitions do not contribute to the structuralstrength and stability of the building and it is therefore safe to demolishthem. The floors do provide some lateral stability to the walls and will not beremoved until an alternative temporary support is not provided to the walls.
3.5 Phase5: Site Reinstatement
After the demolition is complete, the site has to be clearedof remaining debris and decommissioning of site offices and other facilitiesinstalled for the purpose of the site. The site offices and welfare facilitieswill be removed. The state of residual contamination has to be assessed and ifany remedial action needs to be taken, it should be done. The landscapingshould be re-established. Finally, the fencing and screens will be removed andthe site handed-over.
The Principal Contractor should also be aware of thefollowing:
- Traffic Management, an increased awareness is required for traffic control to and from the site from the South and East sides. The South side adjoins a particularly busy road with several shopping complexes further along the road.
- Unauthorised access to site from clinic block
- Unauthorised access from the main roads.
4 Control Measures
4.1 General Health Hazards
4.1.1 Operational Hazards
- Electric shock/burns
- Striking existing services
- Working at height
- Disconnecting of existing services
- Operating machinery, equipment, hand tools and mobile plant
- Hot works
- Manual handling
- Slip, trip, fall type injuries
- Dust / fumes
- Crush type injuries
- Contact with harmful substances
- Working in contaminated ground
- Working in confined spaces
4.1.2 Hazardous Construction Materials
Materials within the project with the potential to cause ahazard to health and safety:
- Fuel oils
- Glass fibre insulation
- Wood treatment products
- Used drainage pipes
- Floor Mastics / glues
The Construction (Design and Management) Regulations came ineffect in UK 31st March 1995. The main duties of the five keyparties (CIRIA, 2001) are:
- The Client - shall appoint a competent planning supervisor and principal contractor for each project
- The Designer - should design structures to avoid, wherever possible, foreseeable risks to health and safety during construction, maintenance and cleaning work. Information should be provided on unavoidable risks. Design includes the preparation of specifications and not limited to calculations and drawings.
- The Planning Supervisor - the organisation or person with overall responsibility for ensuring co-ordination of the health and safety aspects of the design and planning phase, the early stages of the health and safety plan and health and safety file.
- The Principal Contractor - develops the construction-phase health and safety plan and manages and co-ordinates the activities of all contractors to ensure they comply with health and safety legislation. They have duties relating to the provision of information and training on health and safety for everyone on site and the coordination of employees' views working on site.
- Contractors and the Self-Employed - must co-operate with the principal contractor and other contractors and provide relevant information on the risks created by their work and how they will be controlled.
5 References & Bibliography
- Site Safety Handbook, 3rd Edition,CIRIA, 2001
- Brown, D. The Construction (Design and Management regulations 1994: Advice for Designers in Steel, Steel Construction Institute, 1997.
- Holroyd, Trevor M, Site Management for Engineers, Thomas Telford, 1999
- CIRIA, Environmental Handbook for Building and Civil Engineering Projects: Construction Phase, Thomas Telford, 1998
- Managing Demolition and Construction Wastes, Department of the Environment, 1994
- Demolition of Special Structures, The concrete Society, 1984
- Safety in Demolition Work, Health and Safety Executive, 1979