Items where Subject is "B2: Internal fire spread (linings)"
 | Up a level |
- Subjects (24)
- B2: Internal fire spread (linings) (24)
Book Section
In the Secretary of State’s view, requirement B2 is met by achieving a restricted spread of flame
over internal linings. The building fabric should make a limited contribution to fire growth,
including a low rate of heat release.
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.
Requirement B2 does not include guidance on the following.
a. Generation of smoke and fumes.
b. The upper surfaces of floors and stairs.
c. Furniture and fittings.
The surface linings of walls and ceilings should meet the classifications in Table 4.1.
Insulating core panels consist of an inner core of insulation sandwiched between, and bonded to, a membrane, such as galvanised steel or aluminium.
Where they are used internally they can present particular problems with regard to fire spread and should meet all of the following conditions.
a. Panels should be sealed to prevent exposure of the core to a fire. This includes at joints and where services penetrate the panel.
b. In high fire risk areas, such as kitchens, places of special fire hazard, or in proximity to where hot works occur, only class A1 cored panels should be used.
c. Fixing systems for all panels should be designed to take account of the potential for the panel to delaminate. For instance, where panels are used to form a suspended ceiling, the fixing should pass through the panel and support it from the lower face.
Guidance on the control of flame spread is given in the following sections.
a. Stairs and landings: Sections 2 and 3 (escape stairs) and Section 15 (firefighting shafts).
b. Exposed surfaces above fire-protecting suspended ceilings: Section 8.
c. Enclosures to above-ground drainage system pipes: Section 9.
Thermoplastic materials that do not meet the classifications in Table 4.1 can be used as described in paragraphs 4.13 to 4.17. No guidance for European fire test performance is currently available, because there is no generally accepted test and classification procedure.
Thermoplastic materials are defined in Appendix B, paragraph B11. Classifications used here are explained in paragraph B13.
Thermoplastic material classified as a TP(a) rigid product may be used to glaze external windows to rooms, but not external windows to circulation spaces. Approved Document K includes guidance on the safety of glazing.
In rooms and circulation spaces other than protected stairways, rooflights may be constructed of thermoplastic material if they comply with both of the following.
a. The lower surface is classified as TP(a) rigid or TP(b).
b. The size and location of the rooflights follow the limits in Table 4.2, Table 12.2 and Table 12.3.
The following paragraphs apply to lighting diffusers forming part of a ceiling. Diffusers may be part of a luminaire or used below sources of light. The following paragraphs do not apply to diffusers of light fittings attached to the soffit of a ceiling or suspended beneath a ceiling (Diagram 4.1).
Diffusers constructed of thermoplastic material may be incorporated in ceilings to rooms and circulation spaces, but not to protected stairways, if both the following conditions are met.
a. Except for the upper surfaces of the thermoplastic panels, wall and ceiling surfaces exposed in the space above the suspended ceiling should comply with paragraph 4.1.
b. Diffusers should be classified as one of the following.
i. TP(a) rigid – no restrictions on their extent.
ii. TP(b) – limited in their extent (see Table 4.2 and Diagram 4.2).
A ceiling constructed from TP(a) flexible panels should meet the following conditions.
a. Have a maximum area of 5m2.
b. Be supported on all sides.
For the purposes of this requirement, a wall includes both of the following.
a. The internal surface of internal and external glazing (except glazing in doors).
b. Any part of a ceiling which slopes at an angle greater than 70 degrees to the horizontal.
For the purposes of this requirement, a wall does not include any of the following.
a. Doors and door frames.
b. Window frames and frames in which glazing is fitted.
c. Architraves, cover moulds, picture rails, skirtings and similar narrow members.
d. Fireplace surrounds, mantle shelves and fitted furniture.
Parts of walls in rooms may be of lower performance than stated in Table 4.1, but no worse than class D-s3, d2. In any one room, the total area of lower performance wall lining should be less than an area equivalent to half of the room’s floor area, up to a maximum of 20m2 of wall lining.
For the purposes of this requirement, a ceiling includes all of the following.
a. Glazed surfaces.
b. Any part of a wall at 70 degrees or less to the horizontal.
c. The underside of a gallery.
d. The underside of a roof exposed to the room below.
For the purposes of this requirement, a ceiling does not include any of the following.
a. Trap doors and their frames.
b. The frames of windows or rooflights and frames in which glazing is fitted.
c. Architraves, cover moulds, picture rails, exposed beams and similar narrow members.
Rooflights should meet the following classifications, according to material. No guidance for European fire test performance is currently available, because there is no generally accepted test and classification procedure.
a. Non-plastic rooflights should meet the relevant classification in Table 4.1.
b. Plastic rooflights, if the limitations in Table 4.2 and Table 12.2 are observed, should be a minimum class D-s3, d2 rating. Otherwise they should meet the relevant classification in Table 4.1.
Any flexible membrane covering a structure, other than an air-supported structure, should comply with Appendix A of BS 7157.
Guidance on the use of PTFE-based materials for tension-membrane roofs and structures is given in the BRE report BR 274.
Image
Internal fire spread (linings)
B2.(1) To inhibit the spread of fire within the building, the internal linings shall —
(a) adequately resist the spread of flame over their surfaces; and
(b) have, if ignited, either a rate of heat release or a rate of fire growth, which is reasonable in the circumstances.
(2) In this paragraph “internal linings” means the materials or products used in lining any partition, wall, ceiling or other internal structure.
NOTE:
1.Wallcoverings which conform to BS EN 15102, achieving at least class C-s3, d2 and bonded to a class A2-s3, d2 substrate, will also be acceptable.
a. DIFFUSER FORMING PART OF CEILING
b. DIFFUSER IN FITTING BELOW AND NOT FORMING PART OF CEILING
See para 4.15
NOTES:
1. Upper and lower surfaces of suspended ceiling, between plastic panels, to comply with paragraph 4.1.
2. No restriction on class D-s3, d2 diffusers or rooflights in small rooms.
3. See note 4 to Table 4.2. 5m²
See Table 4.2
NOTES:
1. This table does not apply to products that meet the provisions in Table 4.1.
2. Smaller rooflights and diffusers can be grouped together provided that both of the following satisfy the dimensions in Diagram 4.2 or 4.3.
a. The overall size of the group.
b. The space between one group and any others.
3. Lighting diffusers of TP(a) flexible rating should be used only in panels of a maximum of 5m2 each. See paragraph 4.17.
4. There are no limits on the use of class D-s3, d2 materials in small rooms. See Table 4.1.
5. The minimum 3m separation given in Diagram 4.2 between each 5m2 group must be maintained. Therefore, in some cases, it may not be possible to use the maximum percentage quoted.
Materials within this zone – at plane of ceiling – should comply with Table 4.1
Rooflights
See Table 4.2