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multi-storey buildings is a hot issue
Fire safety in
Tim Vincent of Rockwool explains why specifiers should consider non-combustible stone wool insulation in multi- storey buildings
Edward Woods estate in Shepherd’s Bush, west London – a combination of products helped extend the life of three 1960s residential tower blocks
fire safety standards. Given that most fires occur in domestic dwellings, high-rise residential buildings over 18 metres have a high safety risk potential in the event of a fire due to the long escape time for occu- pants to travel from the top of the building to safety. Meanwhile, today’s modern multi-storey buildings tend to offer a complex mix of occupation, including offices, hotels, residential, retail and leisure facilities, which can present further challenges in the event of a fire.
B
Increased fire risk in high-rise buildings
The time to evacuate a high-rise building is extended due to the large volume of people attempting to escape at one time, especially as lifts and escalators are usually inaccessible in the event of a fire. This not only presents problems in terms of the speed of evacuation, it can also put those with mobility issues at an increased risk. In this type of building, fire can quickly spread through the material of an external cladding system or through the cavities. Typically, the source of ignition may be flames issuing from windows or other openings due to a fire within the building, or there may be an external fire source – for example, fire radiation from another building or from a source immediately next to the cladding, such as refuse set alight by arson. Flames in cavities can extend 5 to 10 times original length, regardless of materials present. They can flash over and break out through windows, spread up over or through the cladding or extend over 2 metres above a window opening. There is
uildings over 18 metres in height present numerous challenges when it comes to insulation requirements and
also increased risk during construction when the insulation is exposed. Careful consideration of the design and products specified to reduce the fire risk in such buildings is required with particular emphasis on containment to allow safe evacuation, reduce the risk of fire spread to other buildings and to enable access for fire fighters.
BR 135 and fire safety standards
Fire safety standards, embodied in Building Regulations Part B Fire Safety and associated Approved Documents, are designed to ensure that adequate fire safety provisions are incorporated in tower blocks of whatever type. Regulation B4 requires the external walls of a building to adequately “resist the spread of fire” with functional requirements given in Approved Documents. In any building, the cladding system and materials must conform or exceed the regulation for limited combustibility defined in BR 135: “Fire Performance of External Insulation for Walls of Multi-Storey Buildings”, when tested in accordance with BS 8414-1:2002 and BS 8414-2:2005 for its range of external wall insulation systems. This testing satisfies building regulations in England & Wales and Scotland pertaining to fire for buildings over 18 metres tall. The BR 135 classification is called for as an alternative guidance to non- combustibility compliance for domestic and commercial applications. With the completion of a number of construction projects not compliant with Approved Document B or the guidance under BR 135, the Building Control Alliance in conjunction with its members looked to readdress misunderstandings
Flames in cavities can extend 5 to 10 times original length, regardless of materials present
ADF FEBRUARY 2017
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