What is a pre-demolition survey ?
When a building is to be demolished the (non-domestic) client ( usually the property owner) has a duty to provide pre-demolition information to the designer and contractor. This will involve a pre-demolition investigation and survey.
Before any work commences, a full site investigation must be made by a competent person to determine the hazards and associated risks which may affect the demolition team an members of the community who may pass close to the demolition site.
The competent person is often a specialist structural engineer who will also advise on the temporary support to adjacent buildings and the correct method of dismantling or demolition.
Pre-commencement demolition survey
There are several pre-commencement surveys that may be necessary to ensure the health and safety of all personnel on site. These include:
- A services survey to locate any existing services on site;
- An asbestos survey to identify asbestos-containing materials on site;
- A soil survey to identify contaminated ground; and a ground survey to determine the load-carrying capacity of the ground
The investigation should cover the following topics:
- The construction details of the structures or buildings to be demolished ( including the materials used, fragile roofs, rot and extent of any dilapidation, significance and extent of any dilapidation of the structure, the presence of cantilevered structures and any general weaknesses) and those of neighbouring structures or buildings;
- The identification of key structures elements including pre-and post-tensioned components
- A review of drawings, structure calculations, health and safety file, etc. related to the structure.
- The previous use of the premises
- The load-carrying capacity of adjoining land including the presence of underground culverts;
- The need for possible temporary support structures for the building being demolished and adjoining buildings;
- The location of any dangerous machinery;
- The presence of asbestos, lead or other hazardous or radioactive substances and any associated health risks;
- Environmental issues, such as dust, water pollution and noise;
- Public safety including the provision of high fencing or hoarding;
- Manual handling issues;
- 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 where previously stored;
- The means of access to the site;
- The removal of waste;
- The details of any traffic or pedestrian routes through the site;
- The provision of welfare facilities;
- The proximity of neighbours;
- The location of any public thoroughfares adjacent to the structure or building;
- The age of the structure;
- Its previous use;
- The type of construction;
- Nearby buildings or structures; and the weight of removed materials or machinery on floors above ground level
Details of the structure of the building
The details of the structure of the building to be demolished would include whether it was built of brick. pre-stressed concrete, reinforced concrete or steel. There may be certain building regulations which cover the site and Local Authority Building Department should be contacted to establish whether any part of the site is affected by these regulations. All structural alterations carried out on the structure in the past should be reviewed.
All demolition work requires those in control of the work to produce a written plan showing how the danger will be prevented. This will be the responsibility of the CDM coordinator on notifiable projects and the contractor or designer on non-notifiable demolition projects. The written Health and Safety plan will include a demolition risk assessment of the state and design of the structure to be demolished and the influence of that design on the demolition method proposed. This risk assessment will normally be made by the project designer who will also plan the demolition works. A further risk assessment should then be made by the demolition contractor undertaking the demolition works and a written method statement will be required before demolition of the building takes place.
The demolition project 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, in particular the Control of Asbestos Regulations It may be necessary for the local authority and the police to be consulted about the proposed demolition work so that issues of public protection, local traffic management and possible road closures can be addressed. There should be liaison with the occupiers of addressed. There should be liaison with the occupiers of adjacent properties because, in some cases, they may need to evacuate.