020 RCI 0717

RCI July 2017

RCI TECHNICAL NOTE NUMBER 246 Fire safety: an introduction to Part B B2: internal fire spread (linings) This RCI Technical Note, the first in a series of three Technical Notes, offers a basic introduction to Approved Document B and starts by looking at the 020 JULY 2017 RCIMAG.COM requirements to inhibit the spread of fire within the building The tragedy of the Grenfell Tower fire in London on 14th June has highlighted the urgent need for the roofing and cladding industry to pay closer attention and improve fire safety. Over the coming months lessons will be learnt with the expectation that the regulations will change. This could be a slow process possibly taking a year or so. In the meantime the design and construction of buildings continues, working to the existing regulations. One useful action arising immediately is to increase the general awareness and understanding of what the current regulations require. Approved document B was last amended in 2013 and covers many different aspects of fire safety, some of which are determined by the building designers. For example, the means of warning and escape (Part B1) and the access and facilities for the fire service (Part B5). The remaining parts are of direct relevance to the roofing and cladding industry and include: B2 Internal fire spread (linings) B3 Internal fire spread (structure) B4 External fire spread Part B2 requirement As a fire precaution, all materials used for internal linings of a building should have a low rate of surface flame spread and (in some cases) a low rate of heat release. Classification of linings Lining systems which can be effectively tested for surface spread flame are given a classification. BS 476 Part 7 specifies a method of test for measuring the lateral spread of flame along the surface of a specimen which has been placed in front of an ignited radiation panel. The test lasts for up to 10 minutes. The allowable limit for the spread of flame for a Class 1 product is 165mm. For a Class 3 product the limit is 265mm after 1½ minutes and up to 710mm on completion of the test. The highest product performance classification for a lining material is Class 0, although the regulation notes that this is not a classification identified in any British Standard test. Table A8 in an appendix to Part B gives typical performance ratings of some generic materials and products. Class 0 would include: – any non-combustible material. – brickwork, blockwork, concrete and ceramic tiles. – plasterboard. Class 3 products include: – timber or plywood with a density greater than 400kg/m³. – wood particle board or hardboard. Part B currently gives both our national test methods and also European tests and classifications which differ from the UK national classes. In summary, the guidance is that ‘the lower the classification number the better the resistance to the spread of flame’. Choice of linings Tables in Part B2 set out minimum standards for linings. The choice of materials for walls and ceilings can significantly affect the spread of a fire and its rate of growth. This is particularly important in circulation spaces where linings may offer the main means by which the fire spreads and where rapid spread is most likely to prevent occupants from escaping. Above: Extract from Part B of schedule 1 to the Building Regulations 2010 Table left: ‘Surface linings of walls and ceilings shall meet the given classifications’ “The highest product performance classification for a lining material is Class 0, although the regulation notes that this is not a classification identified in any British Standard test”


RCI July 2017
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