This improves the fire rating of the external structure and further reduces the potential for transmission of heat via the wall or walls. Brickwork is generally a very good fire-resisting material. It is quite possible to achieve periods of resistance of up to four hours, the stability of the material is due to the high temperatures to which it has already been subjected during manufacture. However, there may be problems with large panels (over 4 metres) of brickwork due to differential expansion and movement. In these instances, the restraints being applied to the edges of the panels become critical and the panel can collapse. Distance between buildings Another factor that is considered when assessing external fire spread is the space separation between buildings, or between the building and the property boundary. Depending on proposed separation distances, national, international, federal, or state building regulations may impose various requirements on the nature and type of structure and materials that can be used. Another factor that is dictated by the space separation of buildings is the amount of allowable unprotected openings in the façade of the building. An unprotected opening is any part of the external wall that has a lower fire resistance than the minimum requirement for the wall itself. For example, a window in a brick wall. Relevant codes and standards include: • UK: The Buildings Regulations 2010 Fire Safety Approved Document B • US: NFPA 80A: Recommended Practice for Protection of Buildings from Exterior Fire Exposure • Australia: Building Code of Australia: Building codes of Australia (part of national construction code series) The role of the external walls in protecting escape routes at the boundaries The use and activities undertaken at the premises and surrounding premises will need to be looked at to see what level of fire resistance would be required to prevent fire spread. In some building configurations, such as a courtyard, the potential fire spread could start from one compartment in the building across an open space to another compartment of the same building. This may be relevant if an external wall is of combustible material. Some areas may require stricter controls and higher levels of fire-resistance materials than others. For example, premises used
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