Section B2 Internal Fire Spread (linings)

  1. Requirement
    1. B2 Guidance
      1. Performance
        1. Introduction
        2. B2 Section 3
          1. Classification of linings
            1. Variations and special provisions
              1. Thermoplastic materials

              Requirement

              Internal fire spread (linings)

              B2. (1) To inhibit the spread of fire within the building, the internal linings shall:

              • adequately resist the spread of flame over their surfaces; and
              • have, if ignited, a rate of heat release or a rate of fire growth, which is reasonable in the circumstances.

              (2) In this paragraph ‘internal linings’ mean the materials or products used in lining any partition, wall, ceiling or other internal structure.

              B2 Guidance

              Performance

              In the Secretary of State’s view the Requirements of B2 will be met if the spread of flame 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, so as to limit the contribution that the fabric of the building makes to fire growth. In relation to the European fire tests and classification system, the requirements of B2 will be met if the heat released from the internal linings is restricted by making provision for them to have a resistance to ignition and a rate of fire growth which are reasonable in the circumstances.

              The extent to which this is necessary is dependent on the location of the lining.

              Introduction

              Fire spread and internal linings

              B2.i The choice of materials for 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.
              It is particularly important in circulation spaces where linings may offer the main means by which fire spreads and where rapid spread is 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. This document does not give detailed guidance on other properties, such as the generation of smoke and fumes.

              Floors and stairs

              B2.ii The provisions do not apply to the upper surfaces of floors and stairs because they are not significantly involved in a fire until it is well developed, and thus do not play an important part in fire spread in the early stages of a fire that are most relevant to the safety of occupants.

              Other controls on internal surface properties

              B2.iiiIn Section 7 there is guidance on enclosures to above ground drainage system pipes

              Note: External flame spread is dealt with in Sections 8 to 10.

              Furniture and fittings

              B2.iv Furniture and fittings can have a major effect on fire spread but it is not possible to control them through Building Regulations. They are therefore not dealt with in this Approved Document.

              Classification of performance

              B2.v Appendix A describes the different classes of performance and the appropriate methods of test (see paragraphs 7-20).
              The national classifications used are based on tests in BS 476 Fire tests on building materials and structures, namely BS 476-6:1989 Method of test for fire propagation for products and BS 476-7:1997 Method of test to determine the classification of the surface spread of flame of products. However, BS 476-4:1970 Non- combustibility test for materials and BS 476- 11:1982 Method for assessing the heat emission from building products are also used as one method of meeting Class 0. Other tests are available for classification of thermoplastic materials if they do not have the appropriate rating under BS 476: Part 7; three ratings, referred to as TP(a) rigid and TP(a) flexible and TP(b), are used.

              The European classifications are described in BS 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, namely:

              • BS EN ISO 1182:2002, Reaction to fire tests for building products – Non combustibility test
              • BS EN ISO 1716:2002, Reaction to fire tests for building products – Determination of the gross calorific value
              • BS EN 13823:2002, Reaction to fire tests for building products – Building products excluding floorings exposed to the thermal attack by a single burning item
              • 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 harmonised European fire tests. Until such a 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 A8, in Appendix A, gives typical performance ratings which may be achieved by some generic materials and products.

               

              B2 Section 3

              Wall and ceiling linings

              Classification of linings

              Table 1

              3.1 Subject to the variations and specific provisions described in paragraphs 3.2 to 3.16, the surface linings of walls and ceilings should meet the following classifications:

              Table 1 - Classification of linings Table 1 – Classification of linings

              Definition of walls

              3.2 For the purpose of the performance of wall linings, a wall includes:

              • A. the surface of glazing (except glazing in doors); and
              • B. any part of a ceiling which slopes at an angle of more than 70° to the horizontal.

              But a wall does not include:

              • C. doors and door frames;
              • D. window frames and frames in which glazing is fitted;
              • E. architraves, cover moulds, picture rails, skirtings and similar narrow members; or
              • F. fireplace surrounds, mantle shelves and fitted furniture.
              Definition of ceilings

              3.3 For the purposes of the performance of ceiling linings, a ceiling includes:

              • A. the surface of glazing;
              • B. any part of a wall which slopes at an angle of 70° or less to the horizontal;
              • C. the underside of a gallery; and
              • D. the underside of a roof exposed to the room below.

              But a ceiling does not include:

              • E. trap doors and their frames;
              • F. the frames of windows or rooflights (see Appendix E) and frames in which glazing is fitted; or
              • G. architraves, cover moulds, picture rails, exposed beams and similar narrow members.

               

              Variations and special provisions

              Walls

              3.4 Parts of walls in rooms may be of a poorer performance than specified in paragraph 3.1 (but not poorer than Class 3 (National class) or Class D-s3, d2 (European class) provided the total area of those parts in any one room does not exceed one half of the floor area of the room, subject to a maximum of 20m2.

              Fire-protecting suspended ceilings

              3.5 A suspended ceiling can contribute to the overall fire resistance of a floor/ceiling assembly. Such a ceiling should satisfy paragraph 3.1. It should also meet the provisions of Appendix A, Table A3.

              Fire-resisting ceilings

              3.6 Cavity barriers are needed in some concealed floor or roof spaces (see Section 6), however, this need can be reduced by the use of a fire-resisting ceiling below the cavity.

              Rooflights

              3.7 Rooflights should meet the relevant classification in 3.1. However, plastic rooflights with at least a Class 3 rating may be used where 3.1 calls for a higher standard, provided the limitations in Table 2 and in Table 6 are observed.

              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.

              Thermoplastic materials

              General

              3.8 Thermoplastic materials (see Appendix A, paragraph 17) which cannot meet the performance given in Table 1, can nevertheless be used in windows, rooflights and lighting diffusers in suspended ceilings if they comply with the provisions described in paragraphs 3.10 to 3.14. Flexible thermoplastic material may be used in panels to form a suspended ceiling if it complies with the guidance in paragraph 3.16. The classifications used in paragraphs 3.11 to 3.16, Table 2 and Diagram 9 are explained in Appendix A, paragraph 20.

              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 and internal glazing

              3.9 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 paragraph 3.1.

              Notes:

              1. A ‘wall’ does not include glazing in a door (see paragraph 3.2).
              2. Attention is drawn to the guidance on the safety of glazing in Approved Document N Glazing – safety in relation to impact, opening and cleaning.

              Rooflights

              3.10 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
              • B. the size and disposition of the rooflights accords with the limits in Table 2 and with the guidance to B4 in Table 7.
              Lighting diffusers

              3.11 The following provisions apply to lighting diffusers which form part of a ceiling. They are not concerned with diffusers of light fittings which are attached to the soffit of, or suspended beneath a ceiling (see Diagram 8). 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.

              3.12 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.

              3.13 Subject to the above paragraphs, 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 paragraph 3.1, 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 and Diagram 9.
              Suspended or stretched-skin ceilings

              3.14 The ceiling of a room may be constructed either as a suspended or stretched-skin membrane from panels of a thermoplastic material of the TP(a) flexible classification, provided that it is not part of a fire-resisting ceiling. Each panel should not exceed 5m2 in area and should be supported on all its sides.

              Diagram 8 - Lighting diffuser in relation to ceiling

              Diagram 8 – Lighting diffuser in relation to ceiling

              Table 2 - Limitations applied to thermoplastive rooflights and lighting diffusers in suspended ceilings and Class 3 plasitc rooflights

              Table 2 – Limitations applied to thermoplastic rooflights and lighting diffusers in suspended ceilings and Class 3 plastic rooflights

              Diagram 9 - Layout restrictions on Class 3 plastice rooflights, TP(b) rooflights and TP(b) lighting diffusers

              Diagram 9 – Layout restrictions on Class 3 plastic rooflights, TP(b) rooflights and TP(b) lighting diffusers