Design Guides T 30.001 - Demolition
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| Existing information | Source |
| Historical drawings | Client/current owner, Local Authority [LA], Library, Local Interest Groups, Original Designers and Ordinance Surveys [OS]. |
| Calculations | Client/ Building Owner, Original Designers or LA |
| History of use | Building Owners, Local People |
| Storage on site | Building Owner, Fire Brigade, Environmental Agency |
| Structural Frame | Original Designer, LA |
| Building Materials: strengths, rules for use, etc | Original Design or LA, Design Standards of the time. |
| Hazardous Materials | Original Design, Recent Surveys, Historical Knowledge of Works, Locals |
| Recent Inspections: Use/Abuse/ Neglect | Building Owners |
| Adjoining Structures | Ordinance Survey Maps |
| All statutory service records including [where applicable]:Cables and flood Plain information | Statutory Authorities, Environment Agency |
Table 1: Likely sources of existing information
- b) Information to be obtained: which is absolutely necessary, is usually obtained as part of a site visit and should include:
- i) A contamination survey and chemical analysis- including materials identified;
- ii) An asbestos survey, see Health Series H 10.002 Asbestos
- iii) Soil and water samples and samples from fixed plant and process machines
- iv) Structural inspections of all buildings, structures and boundaries. Also adjacent buildings, which may be affected by the work;
- v) A survey of existing surface treatments, which may contain substances harmful to health, eg, paints used earlier in the century.
Minimise the chances of premature collapse
10. Whenever demolition work of a building or other structure is carried out, there is the potential for premature collapse. Therefore, designers should consider structural stability and include at least the following information with their designs:
- a) The basic structural form;
- b) The framing, if any, and materials;
- c) Construction details, eg, curtailment rules for reinforcement, strength of steel/concrete;
- d) Pre-stressed concrete is particularly difficult to deal with, because of the stored energy in the tendons. It is important to establish whether the pre-stressing tendons are in ducts or cast in;
- e) Load paths: assumed load paths and alternative load paths during the temporary condition;
- f) Identify any critical loading conditions, which could cause collapse;
- g) Identify, unambiguously, any critical load-bearing elements, which should not be removed without a suitable temporary supporting arrangement, eg:
- i) Load-bearing walls;
- ii) Columns under simply supported beams;
- iii) Some columns under continuous beams;
- iv) Floor beams and lintels;
- v) Slabs providing torsional restraint to beams with a significant cantilever in front;
- vi) Members providing lateral restraint to compression members;
- vii) Individual members of trusses.
Information about dealing with the hazards associated with some of this list given in guidance note T 020.005 Refurbishment.
Minimise hazardous temporary situations which have to be managed
11. Temporary situations, which have to be managed, often arise during demolition. While they are often overlooked, they are sources of hazards. Therefore, designers should consider whether the demolition could:
- a) Create retaining wall situations, eg in cellars;
- b) Turning propped cantilever walls into cantilever walls, eg, when floor slabs are demolished;
- c) Create excavations of any depth, eg, demolition of foundations;
- d) Undermine any adjacent structures, eg, when demolishing basement retaining walls;
- e) Destabilise adjacent structures, eg, when demolishing an adjoining structure.
12. In addition, consideration should be given to whether:
- a) Groundwater is likely to be a problem;
- b) Diversion works are required for statutory services before demolition starts;
- c) Any temporary support works for retaining facades cause obstruction to the public or a highway;
13. Other works that fall outside the scope of the demolition can also threaten the stability of structures (e.g. underpinning or creating openings). Designers should consider how structural stability could be maintained in these situations.
Designing to lessen the hazard falling from height
14. Further information is in Technical Series T 20.002 Working at Height.
Designing to lessen the hazard from harmful materials
15. Further information is in Health Series H 10.001 Hazardous Materials and Technical Series T 20.005 Refurbishment.
16. Always check whether asbestos is present and, if it is, what type, its condition and exactly where. Further information is in Health Series H 010.002 Asbestos.
Other hazards
17. Other hazards that may affect a design and should be considered include:
- a) Site restrictions, including:
- i) Access/exit restrictions
- ii) Working hours, eg, consideration for local residents, school pickup times;
- b) Storage areas for deliveries;
- c) Lifting, for which designers should give consideration to:
- i) Whether it is to be by mobile or fixed cranes;
- ii) Whether sufficient area is available to site the crane;
- iii) Whether there are any services under where the crane will operate;
- iv) Whether ground conditions are suitable;
- v) The loads to be lifted over what radius.
- d) Demolition generates dust, noise and vibrations. Therefore, designers should consider how this could affect:
- i) The public and other third parties;
- ii) Adjacent buildings, roads and railways;
- iii) Other sensitive structures, which are close.
- e) Other areas, which will require attention include:
- i) Shutting down existing plant: whether it needs to be in a controlled manner and raw material and products removed;
- f) Whether the demolition process creates a hazard, eg, hot work close to flammable substances;
- g) Radiological hazards: What type and isotope is the source and the means of their safe disposal;
- h) Tipping on the site: is it special waste?
- i) Temporary site roads: is it possible to provide adequate site roads?
USEFUL REFERENCES
Party Wall Act
BS6187: 2000 - Code of Practice for Demolition