Section B2 Internal Fire Spread (Linings)
For the purpose of inhibiting the spread of fire within a building, (linings). the internal linings:
(a) shall have either a rate of heat release or a rate of fire growth and resistance to ignition which is reasonable in
the circumstances
(b) shall offer adequate resistance to the spread of flame over their surfaces.
Performance
The requirement of B2 may be met as follows:
A) In relation to the European fire tests and classification system, the requirement of B2 will be met if the heat released from the internal linings is restricted by making provision for them to have a rate of fire growth and a resistance to ignition which is reasonable in the circumstances or
B) The requirement of B2 may be met if the spread of fire over the internal linings of the building is restricted by making provision for them to have low rates of surface spread of flame and in some cases to have a low rate of heat release or a rate of fire growth, so as to limit the contribution that the fabric of the building makes to fire growth.
The extent to which this is necessary is dependent on the location of the lining.
2.0 Introduction to Provisions
Fire Spread and Lining Materials
2.0.1 The choice of materials for the lining of walls and ceilings can significantly affect the spread of a fire, and its rate of growth, even though they are not likely to be the materials first ignited. This is
particularly important in circulation spaces where linings would offer the main vehicle for fire spread, and where rapid spread would be most likely to prevent occupants from escaping.
Several properties of lining materials influence fire spread. These include the ease of ignition and the rate at which the lining material gives off heat when burning. The guidance relating to the European fire tests and classification provides for control of internal fire spread through control of these properties.
Floors and Stairways
2.0.2 It is impractical to attempt to control the materials used to cover floors and stairways through Building Regulations, and no provisions are made in this Document about them. Attention is directed however to the provisions of the "Code of Practice for Fire Safety of Furnishings and Fittings in Places of Assembly" published by the Department of the
Environment, Heritage and Local Government.
Furniture and Fittings
2.0.3 Furniture and fittings can have a major effect on fire spread but it is impractical to attempt to control them through Building Regulations and no provisions are made in this Document about them. Attention is directed however to the provisions of the "Code of Practice for Fire Safety of Furnishings and Fittings in Places of Assembly" and other guides to fire safety in existing buildings published by the Department of the Environment, Heritage and Local Government.
Other Controls on Linings Properties
2.0.4 There are provisions for the control of fire growth in two other parts of this Document. In B3 there are provisions in sub-section 3.3 for surfaces exposed in concealed spaces above fire-protecting suspended ceilings, and in sub-section 3.4 for enclosures to above-ground drainage system pipes. In B4, there are provisions in sub-section 4.1 concerning the external surface of walls and in subsection 4.3 concerning the surface of rooflights in connection with the performance of roof coverings.
Classification of Performance
2.0.5 Appendix A describes the different classes of performance for materials used as a wall or ceiling lining and the appropriate methods of test, including performance ratings for thermoplastic materials, referred to as TP(a) rigid and TP(b).
The National classifications used are based on tests in BS 476: Parts 6 and 7. Tests in BS 2782 and BS 5438 are used for classification of thermoplastic materials.
The European classifications are described in I.S. EN 13501-1:2002, Fire classification of construction products and building elements, Part 1- Classification using data from reaction to fire tests. They are based on a combination of four European test methods;
I.S. EN ISO 1182: 2002, Reaction to fire tests for building products - Non combustibility test I.S. EN ISO 1716: 2002, Reaction to fire tests for
building products - Determination of the gross calorific value
I.S. EN 13823: 2002, Reaction to fire tests for building products - building products excluding floorings exposed to the thermal attack by a single burning item and
BS EN ISO 11925-2: 2002, Reaction to fire tests for building products, Part 2 - Ignitability when subjected to direct impingement of flame.
For some building products, there is currently no generally accepted guidance on the appropriate procedure for testing and classification in accordance with the European fire tests. Until such time that the appropriate European test and classification methods for these building products are published, classification may only be possible using existing
national test methods.
Table A6 of Appendix A gives typical performance ratings which may be achieved by some generic materials and products.
Assessment of Performance
2.0.6 Combustible linings can contribute significantly to the spread of fire in a building and their use should be restricted. The fire performance
of lining materials is especially important in circulation spaces and on escape routes. An assessment of the likely performance of lining
materials should take account of the following:
the performance of the lining materials in accordance with the criteria indicated in paragraphs A7 to A19 of Appendix A,
the extent and thickness of the lining materials,
the likely interaction between wall and ceiling linings and between linings and any combustible fittings or fixtures,
the extent of voids behind the lining materials and the existence of electrical services in such voids.
Care should be taken to ensure that any products which are used to treat lining materials for the purpose of inhibiting spread of flame are applied, and maintained, strictly in accordance with the specification applicable to the relevant test certification supplied by the manufacturer of such
products.
Surface treatment of linings is not, in general, a suitable method of achieving class B - s3, d2 (European class) or Class 0 (National class)
performance (see A10 of Appendix A). However, in the case of existing lining materials, which satisfy the assessment criteria indicated above, surface treatment to achieve the required performance may be considered.
Care should be taken to ensure that a build up of combustible paints does not reduce the classification of any wall or ceiling lining.
Definitions
2.0.7 The following definitions apply specifically to B2. Other terms applicable more widely throughout the Document are given in Appendix D.
Cavity Means any space enclosed by the elements of a building (including a suspended ceiling) or contained within an element other than a room, cupboard, circulation space, protected shaft or the space within a flue, chute, duct, pipe or conduit.
Ceiling A part of a building which encloses and is exposed overhead in a room or circulation space (the soffit of a rooflight is included as part of its surface, but not the frame).
Circulation space A space (including a protected stairway) mainly used as a means of access between a room and an exit from the building or compartment.
Class 0 See Appendix A, paragraph A11.
RooflightAny domelight, lantern light, skylight or other element intended to admit daylight through a roof.
Room An enclosed space in a building that is not an enclosed circulation space (thus the term includes not only conventional rooms, but also cupboards that are not fittings, and large spaces such as
warehouses and auditoria).
Thermoplastic material See Appendix A, par. A14.
Wall (for the purpose of B2) includes:
(i) the surface of glazing (except glazing in doors), and
(ii) any part of a ceiling which slopes at an angle of 70° or more to the horizontal.
but a wall excludes (for the purpose of B2):
(i) doors and door frames;
(ii) window frames and frames in which glazing is fitted;
(iii) architraves, cover moulds, picture rails, skirtings and similar narrow members; and
(iv) fireplace surrounds, mantle-shelves and fitted furniture.
Provisions meeting the Requirement
2.1 General Provisions
Subject to the variations and specific provisions described in the paragraphs below, the surface linings of walls and ceilings should meet the following classifications -
a. Class D - s3, d2 (European class) or Class 3 (National class) in bathrooms, toilets and shower rooms.
b. Class C - s3, d2 (European class) or Class 1 (National class) in other rooms (except those listed at (e) and (f) below),
c. ClassC - s3, d2 (European class) or Class 1(National class) in circulation spaces within dwellings,
d. Class B - s3, d2 (European class) or Class 0 (National class) in other circulation spaces (including the common areas of flats and maisonettes),
e. Class B - s3, d2 (European class) or Class 0 (National class) in rooms exceeding 30 m2 in Residential (Institutional) and assembly and recreation buildings, and
f. Class B - s3, d2 (European class) or Class 0 (National class) in places of special fire risk (see 1.0.9).
2.2 Variations and Special Provisions
Walls
2.2.1 Part of the surface of a wall in a room may be of a class lower than specified in 2.1, (but not lower than C lass D - s3, d2 (European) or C lass 3 (National)) if the area of that part (or, if there are two or more such parts, the total area of those parts) does not exceed, the lesser of the following:
(i) half the floor area of the room, or
(ii) 20 m2 (in the case of a building or compartment of Purpose Group 1, 2 or 5) or 60 m2 (in any other case); and
In the case of a wall surface in a building of Purpose Group 1, 2, or 5 the area of that part should not exceed 5 m2 and should be separated from any other such part by a distance of not less than 2 m; or
In the case of a wall surface in a building of any other Purpose G roup, the area of that part shall not exceed 15 m2 and should be separated from any other such part by a distance of not less than 2 m.
Fire-protecting Suspended Ceilings
2.2.2 In addition to satisfying the general provisions set out in 2.1, suspended ceilings that can be accepted as contributing to the fire resistance of a floor must also meet the criteria outlined in paragraph A5 and Table A3 to Appendix A.
Fire-resisting Ceilings
2.2.3 The need for cavity barriers in concealed floor or roof spaces, referred to in sub-section 3.3 of B3, can be reduced by the use of a fire-resisting ceiling below the cavity. Such a ceiling should comply with the following:
a. it should have at least 30 minute fire resistance;
b. it should be imperforate except for an opening allowed under par. 3.3.5;
c. it should extend throughout the building or compartment;
d. it should not be demountable; and
e. it should have a Class B - s3, d2 (European class) or C lass 0 (National class) surface on the soffit, and at least a C lass C - s3, d2 (European class) or C lass 1 (National class) surface facing the cavity.
Special Applications
2.2.4. Any flexible membrane covering a structure should comply with the recommendations given in Appendix A of BS 7157:1989 Method of test for ignitability of fabrics used in the construction of large tented structures.
Guidance on the use of PTFE-based materials for tension-membrane roofs and structures is given in a BRE Report Fire Safety of PTFE-based materials used in buildings (BR274, BRE 1994).
2.3 Thermoplastic Materials
2.3.1 Thermoplastic materials (see Appendix A, paragraphs A15, A16) which cannot meet the performance specified in paragraph 2.1 can be used in windows, rooflights and lighting diffusers in ceilings if they comply with the provisions of the following paragraphs:
Note: No guidance is currently possible on the performance requirements in the European fire tests as there is no generally accepted test and classification procedure.
Windows
2.3.2 External windows to rooms (though not to circulation spaces) may be glazed with thermoplastic materials, if the material can be classified as a TP(a) rigid product.
Internal glazing should meet the provisions in par. 2.1 above. Note that a wall does not include glazing in a door.
Rooflights
2.3.3 Rooflights to rooms and circulation spaces (with the exception of protected stairways) may be constructed of a thermoplastic material if:
a. the lower surface has a TP(a) (rigid) or TP(b) classification (see paragraph A15, Appendix A)
b. the size and disposition of the rooflights accords with the limitations in Table 2.1, Diagram 10 and Table 4.5 to Section B4.
Lighting Diffusers
2.3.4 Lighting diffusers are translucent or open structured elements that allow light to pass through. They may be part of a luminaire or used below rooflights or other sources of light. The following provisions apply only to lighting diffusers which form part of a ceiling and are not concerned with diffusers of light fittings which are attached to the soffit of, or suspended beneath a ceiling
Thermoplastic lighting diffusers should not be used in fire protecting or fire resisting ceilings, unless they have been satisfactorily tested as part of the ceiling system that is to be used to provide the appropriate fire protection.
Table 2.1 Limitations applied to thermoplastic lighting diffusers in suspended ceilings and thermoplastic rooflights
Diagram 10 Layout restrictions on TP(b) thermoplastic lighting diffusers and rooflights
Ceilings to rooms and circulation spaces (but not protected stairways) may incorporate thermoplastic lighting diffusers if the following provisions are observed:
a. Wall and ceiling surfaces exposed within the space above the suspended ceiling (other than the upper surfaces of the thermoplastic panels) should comply with the general provisions of par. 2.1, according to the type of space below the suspended ceiling.
b. If the diffusers are of classification TP(a) (rigid),there are no restrictions on their extent.
c. If the diffusers are of classification TP(b), they should be limited in extent as indicated in Table 2.1 and Diagram 10.
d. Thermoplastic materials which have a lesser performance than TP(b) should not be used for lighting diffusers which form part of a ceiling.
