3.13.1 Requirements for Class 0
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Explanations & Illustrations
Clause 3.13.1 : Requirements for Class '0'
( No illustration )
BS 476: Part 6 refers to a standard fire test for propagation of products.
Under this test, there is a means of comparing the contribution of combustible building materials to the growth of a fire by providing a measure of the rate of heat evolution of the samples, exposed in a small combustion chamber.
The performance of each sample is expressed as a numerical index from 0 to 100 or more. Low values of the indexes indicate a low rate of heat release. Three to five specimens are tested.
Index of performance I = i1 + i2 + i3 where sub-index i1 is derived from the first three minutes of test, i2 from the following seven minutes, and i3 from the final ten minutes. A high index i1 indicates an initial rapid ignition and heat release.
Any reference to a surface being Class 0 shall be construed as a requirement that:
a. the material of which the wall or ceiling is constructed shall be non-combustible throughout, or
b. the surface material (or, if it is bonded throughout to a substrate, the surface material in conjunction with the substrate) shall have a surface of Class 1 when tested to BS 476 Part 7 and if tested in accordance with BS 476: Part 6 shall have an index of performance (I) not exceeding 12 and a sub-index (i1) not exceeding 6.
3.13.2 Class other than Class 0
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Explanations & Illustrations
Clause 3.13.2 : Class other than Class 0
( No illustration )
BS 476: Part 7 refers to a standard fire test for the classification of the surface spread of flame of products. This test is able to determine the tendency of surfaces of flat material to support the spread of flame across their surfaces and specifies a method of classification appropriate to wall and ceiling linings. Class 0 represents the best performance, followed in descending order by Class 1, Class 2, Class 3 and Class 4. This clause is rephrased for clarity.
Any reference to a surface being of a class other than Class 0, shall be construed as a requirement that the material which the wall or ceiling is constructed shall comply with the relevant test criteria relating to surface spread of flame, which is specified in relation to that class in BS 476: Part 7.
3.13.3 Order of classification
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Explanations & Illustrations
Clause 3.13.3 : Order of classification
( No illustration )
The reason for having Class 0 is that Class 1 covered too wide a range of performance for use in critical areas. Where a higher degree of protection is required, for example in exit staircases, exit passageways (which constitute the escape route), Class 0 is specified.
Class 0 shall be regarded as the highest class (based on BS 476 Part 6 & 7), followed in descending order by Class 1, Class 2, Class 3 and Class 4 (based on BS 476 Part 7), as set hereunder:
a. Class 0 - Surface of no flame spread. Such surfaces shall conform to the requirements of Cl.3.13.1.
b. Class 1 - Surface of very low flame spread. This refers to surfaces on which during the first 1½ mins of test, the spread of flame does not exceed 165mm and the final spread of flame does not exceed 165mm under the relevant test conditions.
c. Class 2 - Surface of low flame spread. This refers to surfaces on which during the first 1½ mins of test, the spread of flame does not exceed 215mm and the final spread of flame does not exceed 455mm under the relevant test conditions.
d. Class 3 - Surface of medium flame spread. This refers to surfaces on which during the first 1½ mins of test, the spread of flame does not exceed 265mm and the final spread of flame does not exceed 710mm under the relevant test conditions.
e. Class 4 - Surface of rapid flame spread. This refers to surfaces on which the spread of flame exceeded the limit of Class 3.
Effective Date: 10 May 2019
Amendment History
| 3.13.3d |
10 May 2019 |
10 May 2019 |
Change in requirements |
Class 3 - Surface of medium flame spread. This refers to surfaces on which during the first 1½ mins of test, the spread of flame does not exceed 265mm and during the first 10 mins of test is not more than 710mm under the relevant test conditions. |
10 May 2019 |
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3.13.4 Class of flame spread to be not lower than specified
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Explanations & Illustrations
Clause 3.13.4 : Class of flame spread to be not lower than specified
Figure 3.13.4
Wall, ceiling and floor finishes to exit staircase (including exit passageway) shall be of non-combustible materials or Class 0 (sprinkler-protected). For rooms, the extent of wall and ceiling finishes shall comply to Cl.3.13.5a. and b. respectively.
Where a building is protected by automatic sprinkler system, the surfaces of the walls and ceilings of the circulation space (corridor) and institutional occupancy area can be downgraded by 2 classes subject to Class 3 being the lowest.
The surface of a wall or ceiling in a room/space shall be of a class not lower than specified as relevant in the Table 3.13A,
provided that
a. Where an automatic sprinkler system is fitted throughout in the building in compliance with the requirements in Chapter 6, there is no control on the surface of flame rating in rooms/spaces, except for the following occupancies/usage:
(1) healthcare facilities, including hospital, and nursing homes for handicapped, disabled, aged or persons with mental and/or mobility impairments;
(2) detention facilities; and
(3) exit staircases, exit passageways and smoke-free/fire lift lobbies.
b. Where a building is not protected by an automatic sprinkler system, surfaces of the walls and ceilings can be of a surface class not lower than Class 3 to the extent permitted by Cl.3.13.5a. and Cl.3.13.5b. respectively.
c. If timber is used as the surface material for the walls along the side gangways of an auditorium which is not sprinkler-protected, the requirements of this regulation pertaining to the requisite class of flame spread can be relaxed only in respect of those parts of such wall surfaces provided the aggregate area of such parts does not exceed 50% of the whole surface area of the side walls of the auditorium.
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Explanations & Illustrations
Clause 3.13.4c. : Class of flame spread to be
not lower than specified
Figure 3.13.4c.
In the design of the auditorium, there is a need to meet the acoustic requirements. Timber was then considered as a preferred material for use. The above clause provides the relaxation for the use of timber as wall linings, provided the aggregate area of the timber linings does not exceed 50% of the whole surface area of the side walls of the auditorium. The other reason for the above relaxation is that each auditorium is required to be constructed as a fire compartment.
3.13.5 Where class of flame spread can be of any class not lower than Class 3
a. Any part of the surface of a wall in a room or compartment can be of any class not lower than Class 3 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 following
(1) in the case of a building or compartment of PG III, 20m2, or
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Explanations & Illustrations
Clause 3.13.5a.(1) : Where class of flame spread can be of
any class not lower than Class 3
.tmb-firecode.png?Culture=en&sfvrsn=f69efac3_1 "Fg.3.13.5a(1)")
Section
Figure 3.13.5a.(1)
The linings to internal surfaces of a wall in a room or compartment are permitted to have any Class as permitted under Table 3.13A.
(2) in any other case, 60m2.
b. Any part of the surface of a ceiling can be of any class not lower than Class 3 if that part of the surface is the face of a layer of material the other face of which is exposed to the external air (skylight included) and complies with any one of the following:
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Explanations & Illustrations
Clause 3.13.5a.(2) : Where class of flame spread can be of any class not lower than Class 3
-1.tmb-firecode.png?Culture=en&sfvrsn=ed47d1f8_1 "Fg.3.13.5a(2)-1")
Figure 3.13.5a.(2) - 1
Computation of 60m² will be based on total surface areas of walls in a room having not lower than Class 3. In the above diagram, the total surface area of the 4 walls, if finished with Class 3 materials shall not exceed 60m².
-2.tmb-firecode.png?Culture=en&sfvrsn=e08628ba_1 "Fg.3.13.5a(2)-2")
Figure 3.13.5a.(2) - 2
In the above diagram there are two compartments. Each compartment can have a total of 60m² of combustible wall finishes of not lower than Class 3. Subsequently, if the compartment wall is removed, there is a need to review the provision of wall finishes, subject to the total wall finishes to the whole floor shall not exceed 60m². Area of wall finishes in excess of 60m² is required to be removed.
-3.tmb-firecode.png?Culture=en&sfvrsn=1c15ca27_1 "Fg.3.13.5a(2)-3")
Figure 3.13.5a.(2) - 3
In the above diagram, if subsequently the compartment wall as shown in dotted lines is removed, the overall 60m² shall be based on total floor area of compartment A.
-4.tmb-firecode.png?Culture=en&sfvrsn=b83d337b_1 "Fg.3.13.5a(2)-4")
Figure 3.13.5a.(2) - 4
In situation where multiple floors are interconnected to form one compartment by atrium design, waiver application is required to vary the max. 60sq.m
For Class 3 wall finishes, the total area of 60sq.m excludes :
a. door frames and unglazed parts of doors;
b. window frames and frames in which glazing is fitted;
c. architraves cover moulds, picture rails, skirtings and similar narrow members; and
d. fitted furniture.
(1) The ceiling is that of a room in a building or compartment of PG III, IV, V or VII, or is that of a circulation space excluding a smoke-free lobby, exit staircase or exit passageway in a building or compartment of any purpose group, and
(a) the area of that part does not exceed 2.5m²; and
(b) the distance between that part and any other such part is not less than 3.5m.
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Explanations & Illustrations
Clause 3.13.5b.(1) : Where class of flame spread can be of
any class not lower than Class 3
-1.tmb-firecode.png?Culture=en&sfvrsn=e931a968_1 "Fg.3.13.5b(1)-1")
Reflected ceiling plan
Figure 3.13.5b.(1) - 1
Ceilings of living room, dining room, kitchen and bedrooms are permitted to have combustible finishes of class not lower than Class 3. The control is based on the size and spacing of the ceiling material.
-2.tmb-firecode.png?Culture=en&sfvrsn=75cbe19a_1 "Fg.3.13.5b(1)-2")
Reflected ceiling plan
Figure 3.13.5b.(1) - 2
The above clause is intended for lighting diffuser Any part of a ceiling to circulation space e.g. corridor can have not lower than Class 3 flame spread, provided each part shall not exceed 2.5m² and is separated from other such part by minimum 3.5m.
(2) The ceiling is that of a room in a building or compartment of PG VI or VIII, and
(a) the area of that part does not exceed 5m²;
(b) the distance between that part and any other such part is not less than 1.8m; and
(c) that part and all other such parts are evenly distributed over the whole area of the ceiling and together have an area which does not exceed 20% of the floor area of the room.
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Explanations & Illustrations
Clause 3.13.5b.(2) : Where class of flame spread can be of
any class not lower than Class 3
.tmb-firecode.png?Culture=en&sfvrsn=93409e0a_1 "Fg.3.13.5b(2)")
Axonometric view
Figure 3.13.5b.(2)
1. Factories and warehouses are usually provided with translucent roof sheets or sky light for natural lighting.
2. Any part of ceiling which is combustible shall have an area not exceeding 5m² and a class not lower than Class 3 flame spread. It shall be separated from any such part by at least 1.8m.
3. The aggregate area of such part of ceiling shall not exceed 20% of the floor area.
(3) The ceiling is that of a balcony, verandah, open car porch, covered way or loading bay which (regardless of its floor area) has at least one of its longer sides wholly and permanently open.
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Explanations & Illustrations
Clause 3.13.5b.(3) : Where class of flame spread can be of
any class not lower than Class 3
-1.tmb-firecode.png?Culture=en&sfvrsn=80b39dd5_1 "Fg.3.13.5b(3)-1")
Figure 3.13.5b.(3) - 1
-2.tmb-firecode.png?Culture=en&sfvrsn=ee97d1f5_1 "Fg.3.13.5b(3)-2")
Figure 3.13.5b.(3) - 2
Unenclosed loading/unloading platform
-3.tmb-firecode.png?Culture=en&sfvrsn=5fe6a9d3_1 "Fg.3.13.5b(3)-3")
Figure 3.13.5b.(3) - 3
Covered linkway connecting 2 buildings
In-addition to the above, ceilings to balcony, verandah, open carport are also allowed to have not lower than Class 3 flame spread. The above relaxation is allowed as the ceilings are located at the periphery of the building where smoke and
heat could easily be dispersed into the exterior air.
Any material, including gypsum board or plaster board, which satisfies the requirements under Cl.1.4.71 as non-combustible material is to
be treated as acceptable under the above clause, regardless of the presence of the 0.5mm thick paper facing.
(4) The ceiling is that of a garage or outbuilding which (regardless of whether it forms part of a building or is a building which is attached to another building or wholly detached) has a floor area not exceeding 40m2.
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Explanations & Illustrations
Clause 3.13.5b.(4) : Where class of flame spread can be of
any class not lower than Class 3
-1.tmb-firecode.png?Culture=en&sfvrsn=808d21ee_1 "Fg.3.13.5b(4)-1")
Figure 3.13.5b.(4) - 1
Finishes to ceilings in circulation space in the building shall have a surface flame spread rating of not lower than Class 0 as required for under Table 3.13A.
Finishes to ceiling of a room or compartment are permitted to have any class as permitted under Table 3.13A.
-2.tmb-firecode.png?Culture=en&sfvrsn=5f0891c7_1 "Fg.3.13.5b(4)-2")
Figure 3.13.5b.(4) - 2
-3.tmb-firecode.png?Culture=en&sfvrsn=75cd0e8c_1 "Fg.3.13.5b(4)-3")
Figure 3.13.5b.(4) - 3
-4.tmb-firecode.png?Culture=en&sfvrsn=79b1aaa6_1 "Fg.3.13.5b(4)-4")
Figure 3.13.5b.(4) - 4
A garage or outbuilding can have ceiling not lower than Class 3 flame spread, provided the accessible floor area does not exceed 40m².
3.13.6 Exception
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Explanations & Illustrations
Clause 3.13.6 : Exception
( No illustration )
The above clause grants relaxation on the control of wall and ceiling finishes which are not more than 1.0mm thick mounted on non-combustible substrate, provided these finishes are not used in exit staircases and exit passageways. The main concern is
that all protected routes meant for escape of occupants shall be kept free of combustible finishes. The above finishes include material such as gypsum board.
Non-combustible boards, for example gypsum boards, which meet the requirements of Cl.1.4.71 are allowed to be used for the construction of smoke-stop
lobbies, exit staircases and exit passageways.
Wall and ceiling finishes in the form of thin sheet of not more than 1.0mm thickness mounted to a non-combustible substrate will not be subject to the requirement of surface spread of flame provisions, except for exit staircases and passageways.
Composite panel used as wall, ceiling or finishes shall comply with Cl.3.15.13.
