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Last edited 07 Jan 2021
The term ‘combustibility’ refers to the tendency of a substance to burn as a result of fire or chemical reaction. It is can be expressed as a property that is a measure of how easily a substance will ignite or burn, an important consideration when materials are being used or stored for construction purposes.
The term ‘flammable’ may be used to describe substances that ignite more easily, whilst substances that are harder to ignite or that burn less intensely may be referred to as combustible. For more information see: Flammable.
Less combustible materials may be described as 'materials of limited combustibility'. Approved document B of the building regulations defines limited combustibility as: 'a material performance specification that includes non-combustible materials, and for which the relevant test criteria are set out in Appendix A, paragraph 9.'
- Any material which when tested to BS 476-11:1982 (2007) does not flame nor cause any rise in temperature on either the centre (specimen) or furnace thermocouples.
- Products classified as non-combustible in tests following the procedures in BS 476-4:1970 (2007).
- Any material classified as class A1 in accordance with BS EN 13501-1:2002 Fire classification of construction products and building elements. Classification using data from reaction to fire tests.
Following the Grenfell Tower Fire, a decision was taken to ban combustible materials in the cladding for buildings over 18m in height. The following change to approved document 7 came into force on 21 December 2018.
|The Building Regulations restrict the use of combustible materials in the external walls of certain buildings over 18m in height. Refer to regulation 7(2) of the Building Regulations and to Approved Document B: volume 2, part B4 for details.|
The issue was raised again in November 2019 following a fire at The Cube in Bolton. In this case HPL cladding was used, and the building was less than 18m in height, resulting in calls for the ban on combustible cladding materials to be extended. For more information see: The Cube.
On 27th November 2019, after a challenge to the consultation process that introduced the ban, the High Court ruled that the consultation had been inadequate in respect of the inclusion of products intended to reduce heat gain within a building (for example, blinds, shutters and awnings) within the ban. As a result the Court quashed one part of the 2018 regulations which had included within the ban ”a device for reducing heat gain within a building by deflecting sunlight which is attached to an external wall”. The practical effect of the Court judgment is that the regulations now exist as if that section of the regulations had never been included in the ban. Ref https://www.gov.uk/government/publications/building-amendment-regulations-2018-circular-032019
 Related articles on Designing Buildings Wiki
- Approved Document B.
- Approved Document J.
- BS 476.
- BS EN 13501-1.
- Consultation on banning the use of combustible materials in the external walls of high-rise residential buildings.
- Combustion appliance.
- Combustion plant.
- Fire safety design.
- Flammable building materials.
- Limited combustibility.
- Non-combustible material.
- The Cube.
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