DEMOLITION PROCESSES AND METHODS
As an intrinsic part of the construction process, efficient demolition of structures is an important factor deserving careful consideration in the evolution of any redevelopment project.
Modern emphasis is on reduction of construction periods to ensure economic redevelopment, coupled with increasing town centre regenerating calling for careful demolition on constructed and restricted site, have resulted in more consideration being given to demolition as part of the process of construction and redevelopment than was typical in previous times.
Developing a Demolition Strategy
The strategy will need to take into account the method of construction used for the original building and its proximity to other buildings, structures and the general public. These factors, together with location, the cost and availability of tipping and disposal and the desirability and economics of reuse, must be taken into account in the development of an appropriate strategy for the demolition of a structure.
Information on buildings in terms of “as built” drawings and structural details may often be unavailable or unreliable, and consequently some investigative site and desk work may be necessary, both to ascertain the way in which the building was originally constructed, and to identify the stresses and strains which exist within it.
In order to plan the most efficient method of demolition, it is important to have a full understanding of the method of construction and the stress patterns imposed upon the building.
Failure to do so may result in risks to the safety of both those involved in the demolition and those in close proximity to the site.
Selecting Appropriate Techniques
Majors factors to be considered in selecting an appropriate technique include: –
- Safety of personnel and public
- Working Methods
- Legislation applicable
- Insurance Cover
Preliminary Aspects Prior to Site Demolition Work
Considerations should be given to:
- Conducting a site and building survey, with a structural bias;
- The examination of drawings and details of existing construction where
- The preparation of details and drawings from site survey activities where no
- such information is available;
- Establishing previous use of premises, especially with regard to flammable substances or substances hazardous to health or safety;
- Programming the sequence of demolition work;
- The preparation of a Method Statement.
A detailed health and safety method statement, produced before work starts, is essential for safe working. It should include a full risk assessment, identify problems and their solutions, and form a reference for the site supervision.
The method statement should be easy to understand, agreed by and known to all levels of management and supervision, and should include such matters as: –
- The sequence and method of demolition or dismantling of the building or structure with details of personnel access, working platforms and machinery requirements;
- Details and design of any temporary supporting structures to be used during the demolition process;
- Specific details of any pre-weakening on structures which are to be pulled down or demolished with explosives;
- Arrangements for the protection of personnel and the public and the exclusion of unauthorized persons, with details of areas outside the site boundaries that may occasionally need to be controlled to improve safety during critical aspects of the work;
- Details of the removal or making safe of electrical, gas and other services and drains;
- Details of the temporary services available or required for the contractor’s use;
- Details of the methods for detailing with flammable materials and gases which may have been retained or deposited as residue in process machinery, pipework or storage;
- Details of methods to establish the presence of hidden or other substances that may be hazardous to health, the methods to be used for their disposal, and any necessary protective equipment;
- Arrangements for the control of site transport used for the removal of demolition debris.
In many circumstances, buildings and structures should be demolished in the reverse order to their erection; although where partial demolition is involved, a more careful evaluation of the nature of the effects of the demolition is necessary.
Normally, the demolition contractor is able to adopt a method of work which: –
- Gradually reduces the height of the building; or
- Arranges the deliberate controlled collapse of the building or structure so that work can be completed at ground level.
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