2.5 Internal linings
The building contents are likely to be the first items ignited in a fire and are beyond the scope of this guidance. Materials used in walls and ceilings can however significantly affect the spread of fire and its rate of growth. Fire spread on internal linings in escape routes is particularly important because rapid fire spread in protected zones and unprotected zones could prevent the occupants from escaping.
Wall and ceiling surfaces mean the substrate or lining material including any treatment thereof to restrict flame spread, but excludes any decorative wallpaper or paints. Whilst it is accepted that such wallpaper or paints are not controlled by the guidance, multiple layers applied to the face of a wall or ceiling surface can increase flame spread and hence the fire growth rate. For this reason, multiple layers are not recommended when carrying out refurbishment work involving the re-decoration of wall and ceiling surfaces.
Limitations on higher risk surfaces - a room (other than a kitchen) not more than 4m2 may have wall and ceiling linings with a high risk classification. In a room (other than a kitchen) more than 4m2 the wall surfaces may also have a high risk classification subject to a maximum of 20m2 where the total area of the high risk surfaces is not more than half the floor area of the room.
Wall and ceiling linings should be assessed for their reaction to fire characteristics.
Wall linings - the following wall surfaces should be included in the assessment:
However the following surfaces need not be taken into account:
doors and door frames
window frames and frames in which glazing is fitted
skirtings and facings, cover moulds, picture rails, and similar narrow members, or
fireplace surrounds, mantle shelves and fitted furniture.
Ceiling linings - the following ceiling surfaces should be included in the assessment:
the surface of glazing, and
any part of a ceiling which slopes at an angle of 70º or less to the horizontal.
However the following need not be taken into account:
ceiling hatches and their frames, and
the frames of windows or rooflights and the frames in which glazing is fitted, or
facings, cover moulds, picture rails, and similar narrow members.
rigid solid PVC (uPVC), or
polycarbonate rigid solid sheet at least 3mm thick, or
multi-skin polycarbonate sheet at least 10mm thick overall which has low or medium risk.
Thermoplastic materials in ceilings, rooflights and lighting diffusers provide a significant hazard in a fire. Burning droplets can rapidly increase the fire growth rate and the smoke produced is normally dense and toxic which combine to produce extremely hazardous conditions. For these reasons, thermoplastic material should not be used in protected zones or fire-fighting shafts. However thermoplastic materials may still be used with limited application for some ceilings (see clause 2.5.5), rooflights (see clause 2.5.6) or light fittings with diffusers (see clause 2.5.7).
A thermoplastic material means any synthetic material that has a softening point below 200º C when tested in accordance with BS EN ISO 306: 2004 Method A120 Plastics - Thermoplastic Materials - Determination of Vicat softening temperature.
Rigid Thermoplastic TP(a) rigid means:
rigid solid (solid as distinct from double or multiple-skin) polycarbonate sheet at least 3mm thick, or
multi-skinned rigid sheet made from unplasticised pvc or polycarbonate which has low or medium risk for reaction to fire, or
any other rigid thermoplastic product, a specimen of which (at the thickness of the product as put on the market), when tested in accordance with Method 508A in BS 2782: 2004 performs so that the test flame extinguishes before the first mark, and the duration of flaming or afterglow does not exceed 5 seconds following removal of the burner.
Flexible Thermoplastic TP(a) flexible means:
flexible products not more than 1mm thick which satisfy the Type C provisions of BS 5867: Part 2: 1980 (1993) when tested in accordance with Test 2 in BS 5438: 1989 (1995) with the flame applied to the surface of the specimens for 5, 15, 20 and 30 seconds respectively, but excluding cleansing procedure.
Semi-rigid Thermoplastic TP(b) semi-rigid means:
a rigid solid polycarbonate sheet product not more than 3mm thick, or multiple-skin polycarbonate sheet products which do not qualify as TP(a) by test, or
other products which, when a specimen of the material more than 1.5mm and not more than 3mm thick is tested in accordance with Method 508A in BS 2782: 2004, has a rate of burning which is not more than 50mm/minute.
A ceiling constructed from thermoplastic materials, either as a suspended or stretched skin membrane with a TP(a) flexible classification should be supported on all its sides and each panel should not exceed 5m2. However this does not apply to a ceiling which has been satisfactorily tested as part of a fire resisting ceiling system. A ceiling with a TP(a) flexible classification should not be installed in the ceiling of a protected zone or fire-fighting shaft.
Subject to the recommendations in clauses 2.5.6 and 2.5.7, the use of thermoplastic materials with a TP(a) rigid or TP(b) semi-rigid classification is unlimited.
Thermoplastic materials (other than TP(a) flexible) may be used in rooflights subject to the recommendations in the table and diagram below.
Thermoplastic rooflights should also be constructed in accordance with the guidance to Standard 2.8.
Thermoplastic materials may be used in light fittings with diffusers. Where the lighting diffuser forms an integral part of the ceiling, the size and disposition of the lighting diffusers should be installed in accordance with the table and diagram below.
However where the lighting diffuser form an integral part of a fire-resisting ceiling which has been satisfactorily tested, the amount of thermoplastic material is unlimited.
Where light fittings with thermoplastic diffusers do not form an integral part of the ceiling, the amount of thermoplastic material is unlimited provided the lighting diffuser is designed to fall out of its mounting when softened by heat.
Table 2.2. Thermoplastic rooflights and light fittings with diffusers
|Protected zone or fire-fighting shaft||Unprotected zone and protected enclosure||Room|
|Classification of lower surface||Any thermo-plastic||TP(a) rigid||TP(a) flexible and TP(b)||TP(a) rigid||TP(a) flexible and TP(b)||TP(b)|
|Maximum area of each diffuser panel or rooflight (m2)||Not advised||No limit||5m2||No limit||5m2||1m2|
|Maximum total area of diffuser panels or rooflights as a percentage of the floor area of the space in which the ceiling is located (%)||Not advised||No limit||15%||No limit||50%||50%|
|Minimum separation distance between diffuser panels or rooflights (m)||Not advised||No limit||3m||No limit||3m||A distance equal to the largest plan dimension of the largest diffuser or rooflight (see figure 2.2)|
Smaller panels can be grouped together provided that the overall size of the group and the space between any others, satisfies the dimensions shown in figure 2.1 below.
The minimum 3m separation in the diagram below should be maintained between each 5m2 panel. In some cases therefore, it may not be possible to use the maximum percentage quoted.
TP(a) flexible is not recommended in rooflights.
X = Maximum dimension of the largest diffuser or rooflight above.
Y = Maximum dimension of the smallest diffuser or rooflight above.
A sandwich panel is a factory-made, non load-bearing component of a wall, ceiling or roof consisting of a panel having an insulated core filling the entire area between sheet metal outer facings, which may or may not have decorative and/or weatherproof coatings.
A sandwich panel used for internal walls or linings should have a non-combustible classification.