3.11.1 General provision
R
Rationale - Clause 3.11.1
Concealed spaces or cavities in a building provide a ready route or flue for smoke and flame to spread undetected, thus increasing the risk to life safety of occupants in the building. This is particularly so in the case of void spaces above a suspended ceiling, in a roof space or in a raised floor system. Therefore, cavity barriers constructed of fire-rated materials shall be provided to prevent the spread of smoke and fire in the concealed spaces.
E
Explanations & Illustrations
Clause 3.11.1 : General provision
Section
Figure 3.11.1 - 1
Section
Figure 3.11.1 - 2
Concealed spaces or cavities in building provide a ready route or flue for smoke and flame to spread undetected for quite some time, thus increasing the risk to life safety of occupants in the building. This is particularly so in the case of void
spaces above a suspended ceiling or in a roof space or in a raised floor system. Provisions are available in the Fire Code to reduce the risk of concealed smoke and flame spread by the introduction of cavity barrier when the area or linear dimensions
of cavities exceed the limits as per Table 3.11A. Cavity barriers
shall be constructed of non-combustible materials and shall have at least ½-hr fire resistance.
Concealed spaces in a building, such as those within suspended ceilings or raised floors, shall be sub-divided by construction of cavity barriers to restrict the spread of smoke and flames.
3.11.2 Closing the edges of cavities
E
Explanations & Illustrations
Clause 3.11.2 : Closing the edges of cavities
Figure 3.11.2 - 1
Section
Figure 3.11.2 - 2
“Cavity barrier” means any construction provided to close a cavity against, or restrict the spread of smoke and flame within it.
In Figure 3.11.2 - 1 above, cavity barriers are used to close the edges around the window opening. Similar application is provided to window in external cavity wall in Figure 3.11.2 - 2.
Cavity barriers shall be used to close the edges of cavities, edges around openings through a wall, floor and any other part of the construction which contains a cavity and to separate any cavity in a wall, floor or any other part of the construction from any other such cavity.
3.11.3 Interrupting cavities
E
Explanations & Illustrations
Clause 3.11.3 : Interrupting cavities
Figure 3.11.3 - 1
Cavities must be closed where the fire barrier elements (compartment walls) abut the cavity (including the frame of a door).
Section
Figure 3.11.3 - 2
Cavity in the walls shall be closed where the compartment floor abuts it.
Figure 3.11.3 - 3
Any cavity within an element, or at the junction of two elements, must be closed by a cavity barrier.
Section
Figure 3.11.3 - 4
It is a common practice to bring the compartment wall right-up to the underside of the structural slab above. The cavity barrier above the compartment wall shall be treated as an extension of the compartment wall below.
Section
Figure 3.11.3 - 5
The roof space over a protected staircase must be separated by either a cavity barrier at (a) having the same fire rating as the wall of the staircase below, or a fire-rated ceiling at (b). See Cl.1.4.18 for further illustration. Extending the masonry wall right up to the underside of the roof coverings at (a) would meet the requirement under Cl.3.10 of having masonry enclosure to exit staircase.
If a fire-resistant barrier (such as a compartment wall, floor, ceiling or roof) abuts a cavity (including a roof space), such a barrier shall be extended to sub-divide the cavity to form a complete fire resistant barrier. Such cavity barriers shall be of fire resisting construction at least equal to the provision for that required of the fire resisting barrier.
3.11.4 Sub-division of extensive cavities
Cavities, including roof spaces, unless otherwise permitted, shall be sub-divided so that the maximum distance between cavity barriers shall not exceed the relevant dimensions given under Table 3.11A.
3.11.5 Fire resistance and fixing of cavity barriers
E
Explanations & Illustrations
Clause 3.11.5 : Fire resistance & fixing of cavity barriers
Section
Figure 3.11.5 - 1
Cavity barriers must be tightly fitted to rigid construction and mechanically fixed in position wherever possible. Where this is not possible (for example, in the case of a junction with slates tiles, corrugated sheeting or similar materials) the junction should be fire-stopped to prevent the spread of fire and smoke in the concealed space.
Cavity barriers must also be fixed so that performance will not be made ineffective by:
a. movement of the building due to subsidence, shrinkage or temperature change;
b. collapse in fire of any services penetrating them;
c. failure in fire of fixings; and
d. failure in fire of any material or construction which they may abut. For example, if a suspended ceiling is continued over the top of a fire-resisting wall or partition, and direct connection is made between the ceiling and the cavity barrier above the line of the wall or partition, premature failure of the cavity barrier can occur when the ceiling collapses. However, this does not arise if the ceiling is designed to provide fire protection of 30 minutes or more.
failure in fire of any material or construction which they may abut. For example, if a suspended ceiling is continued over the top of a fire-resisting wall or partition, and direct connection is made between the ceiling and the cavity barrier above the line of the wall or partition, premature failure of the cavity barrier can occur when the ceiling collapses. However, this does not arise if the ceiling is designed to provide fire protection of 30 minutes or more.
Section
Figure 3.11.5 - 2
The main purposes of extending the compartment walls into the ceiling space are to complete the compartmentation to each apartment unit and to prevent smoke and fire spread via the concealed ceiling space.
Section
Figure 3.11.5 - 3
Compartment walls should be carried right up to the full storey height, to a compartment floor above or to the roof coverings, as appropriate. The walls in the ceiling above the common corridor shall not be treated as cavity barriers. They shall be treated as extension of the compartment walls below.
The main purposes of extending the compartment walls into the ceiling space are to complete the compartmentation to each apartment unit and to prevent smoke and fire spread via the concealed ceiling space.
Cavity barriers shall be:
a. constructed to provide at least ½-hr fire resistance rating; and
b. tightly fitted to rigid construction or the junctions shall be fire-stopped to comply with the requirements of Cl.3.12.
3.11.6 Openings in cavity barriers
E
Explanations & Illustrations
Clause 3.11.6 : Openings in cavity barriers
Figure 3.11.6 - 1
Figure 3.11.6 - 2
Penetrations of cavity barriers shall be restricted to those illustrated above. All openings through cavity barriers must be no larger than necessary and be fire stopped. The fire stopping shall not restrict thermal movement.
A cavity barrier shall have no opening except for:
a. a door which has the same fire resistance rating as the cavity barrier, and are kept closed all the times;
b. a pipe which complies with the provision under Cl.3.9.3;
c. a cable or conduit containing one or more cables;
d. a duct which is fitted with suitably mounted automatic fire damper where it passes through the cavity barrier; and
e. other openings fitted with a suitably mounted fire damper.
3.11.7 Raised floors for fixed stages and display platforms
E
The construction of raised floors for fixed stages and display platforms shall comply with the following requirements:
a. the concealed space between the structural floor and raised floor shall not be used for storage;
b. no services or installation shall be permitted within the concealed space other than electrical wiring in conduit in compliance with the requirements of SS 638;
c. all sides of the raised floor shall be properly sealed; and
d. the concealed space shall be subdivided by cavity barriers in compliance with the requirements of Cl.3.11.4 and Table 3.11A.
3.11.8 Raised floors with or without accessible panels
The construction of raised floors with or without accessible panels shall comply with all of the following requirements:
a. The supporting structure shall be constructed of non-combustible materials having a melting point of at least 750°C.
b. The concealed space between the structural floor and raised floor shall not be used for storage.
c. No services or installations shall be permitted within the concealed space other than:
(1) electrical wiring in metal conduit and metal trunking in compliance with the requirements of SS 638;
(2) communication cables for computer equipment; and
(3) fire protection installations serving the area.
d. Where the raised floor is used as a plenum, requirements in Cl.7.1.4 shall be satisfied.
Effective Date: 10 May 2019
Amendment History
| 3.11.8a |
10 May 2019 |
10 May 2019 |
Change in requirements |
The supporting structure shall be constructed of non-combustible materials having a melting point of at least 800°C. |
10 May 2019 |
Download
|
e. Decking of the raised floor shall be constructed of non-combustible material. Where combustible material is used as core material, if allowed in the case of sprinkler-protected buildings, the top, bottom, all sides and cut edges shall be covered with material with surface property complying with Class 0 (excluding materials for floor finishes).
f. In the case of raised floors with accessible panels, access sections or panels shall be provided such that all concealed spaces between the structural floor and raised floor are easily accessible.
E
Explanations & Illustrations
Clause 3.11.8e. : Raised floors with or without accessible panels
Figure 3.11.8e. - 1
Non-combustible raised floor panels and supports are allowed to be used in non-sprinkler or sprinkler-protected buildings.
Figure 3.11.8e. - 2
Raised floor panel constructed of combustible core, e.g. chipboard, shall only be allowed to be used in buildings protected by sprinkler system and that the underside of the raised floor is adequately covered by the sprinkler system.
g. Openings in the raised floor for entry of electrical cables shall be effectively closed to prevent entry of debris or other combustible material into the concealed spaces.
h. All sides of the raised floor shall be properly sealed.
i. the concealed space shall be subdivided by cavity barriers such that the maximum unobstructed area within the concealed space does not exceed 930m2.
j. Where the concealed space is fitted with an automatic sprinkler system which complies with the requirements in Chapter 6, cavity barriers are not required.
k. For a non-sprinkler-protected building, if the height of the concealed space measured between the top of the structural floor and underside of the raised floor decking exceeds 150mm, it shall be fitted with an automatic smoke detection system complying with requirements of SS 645. For a sprinkler-protected building, the concealed space shall be fitted with an automatic smoke detection system as above if its height is between 150mm to 400mm, and automatic sprinkler system if it exceeds 400mm; and
l. Where the height of concealed space measured between the top of the structural floor and the underside of the raised floor decking is less than 50mm, the requirements on provision of cavity barriers shall not be applicable.
E
Explanations & Illustrations
Clause 3.11.8g. to j. : Raised floors with or
without accessible panels
Figure 3.11.8g. to j.
The provision of cavity barriers shall comply with Table 3.11A of the
Fire Code.
Non-sprinkler protected building
Cavity barriers shall be provided in accordance with Table 3.11A. The
height of concealed space (H), measured between the finished floor level and the underside of the raised floor decking shall not exceed 400mm. The concealed space shall be fitted with smoke detection system in accordance with SS CP 10 Code of Practice
for the Installation and Servicing of Electrical fire Alarm Systems. SS CP 10 also allows that smoke detector system is not required to be provided in concealed space which does not exceed 150mm in height. Automatic smoke detection system is applicable
if the height of concealed space exceeds 400mm.
Sprinkler protected building
Cavity barriers shall be provided in accordance with Table 3.11A. Where
the height of the concealed space does not exceed 400mm, smoke detection system complying with SS CP 10 shall be provided. The height of concealed space may exceed 400mm if the space is fitted throughout with sprinkler system. Where sprinkler system
is provided inside the concealed space, cavity barriers are not required to be provided – Cl.3.11.8j..
3.11.9 Provision for concealed spaces between floor or roof and suspended ceilings
Provision of cavity barriers within the concealed spaces of suspended ceiling can be exempted provided all of the following requirements are complied with:
a. The concealed space shall not be used for storage.
b. The supporting elements shall be constructed of non-combustible material.
c. The exposed surfaces within the concealed space is of Class 0 flame spread (excluding surfaces of any pipe, cable, conduit or insulation of any pipe).
d. In the case of a detector protected building:
(1) if the concealed space does not exceed 800mm in depth, or
(2) if the concealed space is fitted with detectors which comply with the requirements of Chapter 6.
E
Explanations & Illustrations
Clause 3.11.9d. : Provision for concealed spaces between
floor or roof & suspended ceilings
Figure 3.11.9d. : Detector protected building (non-sprinkler protected)
Provision of cavity barriers in concealed ceiling space may not required if the following requirements are complied with:
a. the space is not used for storage purpose;
b. the supporting elements eg. ceiling hangers or supports are constructed of non-combustible material;
c. the exposed surfaces within the concealed space is of Class 0 flame spread (excluding surfaces of any pipe, cable, conduit or insulation of any pipe or duct); and
d. concealed space does not exceed 800mm in depth; if exceeds 800mm, it shall be fitted with smoke or heat detectors.
e. In the case of a sprinkler-protected building:
(1) if the concealed space does not exceed 400mm in depth, or
E
Explanations & Illustrations
Clause 3.11.9e.(1) : Provision for concealed spaces between
floor or roof & suspended ceilings
.tmb-firecode.png?Culture=en&sfvrsn=699d2db7_1 "Fg.3.11.9e(2)")
Figure 3.11.9e.(1). : Sprinkler-protected building - Depth of ceiling space does not exceed 400mm
Provision of cavity barriers in the concealed ceiling space may not required if the following are complied with:
a. the space is not used for storage purpose;
b. the supporting elements eg. ceiling hangers or supports are constructed of non-combustible material;
c. the exposed surfaces within the concealed space is of Class 0 flame spread (excluding surfaces of any pipe, cable, conduit or insulation of any pipe or duct); and
d. concealed space does not exceed 400mm in depth.
(2) if the concealed space exceeds 400mm and does not exceed 800mm in depth and no combustible material is used within the concealed space, or
E
Explanations & Illustrations
Clause 3.11.9e.(2) : Provision for concealed spaces between
floor or roof & suspended ceilings
.tmb-firecode.png?Culture=en&sfvrsn=b7d265b9_1 "Fg.3.11.9e(3)")
Figure 3.11.9e.(2) : Sprinkler-protected building - Depth of ceiling space exceeds 400mm but not exceeding 800mm
Provision of cavity barriers in the concealed ceiling space may not required if the following are complied with:
a. the space is not used for storage purpose;
b. the supporting elements e.g. ceiling hangers or supports are constructed of non-combustible material;
c. the exposed surfaces within the concealed space is of Class 0 flame spread (excluding surfaces of any pipe, cable, conduit or insulation of any pipe or duct); and
d. no combustible material is used within the concealed space. However, where the combustible content is small in quantity, the SCDF may, at its discretion grants exemption, provided the space is protected by sprinklers installed on the extended basis under SS CP 52 (whole coverage to be extended to the ceiling).
(3) if the concealed space is fitted with an automatic sprinkler system which complies with the requirements of Chapter 6.
E
Explanations & Illustrations
Clause 3.11.9e.(3) : Provision for concealed spaces between
floor or roof & suspended ceilings
.tmb-firecode.png?Culture=en&sfvrsn=901e0b28_1 "Fg.3.11.9e(1)")
Figure 3.11.9e.(3) : Concealed space is sprinkler-protected in accordance with Chapter 6
Provision of cavity barriers in the concealed ceiling is not required. See also Cl.3.11.10 for further relaxation.
f. In the case of other buildings, the concealed space shall not exceed 800mm in depth.
E
Explanations & Illustrations
Clause 3.11.9f. : Provision for concealed spaces between
floor or roof & suspended ceilings
Figure 3.11.9f. : Other building which neither requires detector nor sprinkler system
Provision of cavity barriers in the concealed ceiling space may not required if the following are complied with:
a. the space is not used for storage purpose;
b. the supporting elements e.g. ceiling hangers or supports are constructed of non-combustible material;
c. the exposed surfaces within the concealed space is of Class 0 flame spread (excluding surfaces of any pipe, cable, conduit or insulation of any pipe or duct); and
d. concealed space does not exceed 800mm in depth; if exceeds 800mm, it shall be fitted with smoke or heat detectors.
3.11.10 Exemption of cavity barriers in ceiling space
E
Explanations & Illustrations
Clause 3.11.10 : Exemption of cavity barriers in ceiling space
( No illustration )
1. Where the concealed ceiling space is protected by automatic sprinkler system, the above clause allows the following:
a. Provision of cavity barrier is exempted;
b. Combustible materials such as hardwood timber hangers for ceiling; and
c. Exposed surfaces within the ceiling space may be of any class other than Class 0 flame spread ie. timber members.
2. The above relaxation shall not apply if the above ceiling construction is situated over an exit passageway or other designated means of escape facilities.
Where the concealed space of suspended ceiling is fitted with an automatic sprinkler system which complies with the requirements in Chapter 6,
a. the concealed space can be exempted from provision of cavity barriers; and
b. combustible materials can be used for the supporting elements and exposed surfaces of materials within the concealed space, provided the ceiling is not situated over an exit passageway, smoke-free lobby or other designated means of escape facilities.
3.11.11 Suspended ceiling over protected areas
E
Explanations & Illustrations
Clause 3.11.11 : Suspended ceiling over protected areas
Section
Figure 3.11.11
The main concern is that spaces meant for safe escape of occupants shall be kept free of combustible materials. Common corridors are treated as escape routes. The exposed surfaces within ceiling space shall have a flame spread rating of Class ‘0’.
The concealed spaces of a suspended ceiling over an exit passageway, smoke-stop lobby, exit staircase or other designated means of escape facilities shall comply with the following:
a. the ceiling supporting elements and the ceiling shall be constructed of non-combustible materials.
b. the exposed surfaces within the concealed space shall be of Class 0 surface flame spread; and
c. where sprinkler system is installed within the concealed spaces at smoke-free lobby/ fire lift lobby, the ceiling supporting elements and its exposed surface may have a surface spread of flame not lower than Class 2.
Buildings under PG I are not required to comply with the requirements on the provision of cavity barriers in concealed spaces. Residential units in buildings under PG II need not comply with requirements on the provision of cavity barriers in concealed floor and ceiling spaces.
