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Legend: Explanations & Illustrations Rationale Note Revision history Print

CLAUSE 3.8 PROTECTED SHAFTS

3.8.1 Purpose of protected shaft

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A protected shaft shall not be used for any purpose additional to those given as defined under Cl.1.4.82. All services such as, pipe/duct installation shall not be located inside a protected staircase,unless otherwise permitted in Cl.3.8.7. Likewise, no washroom is allowed to be located inside protected staircase.

3.8.2 Requirements of protected shaft

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Every protected shaft shall be required to:

a. form a complete barrier to fire between the different compartments which the shaft connects;

b. have the appropriate fire resistance to comply with the requirements of Cl.3.3; and

c. be constructed of non-combustible material (together with any beam or column which forms part of the enclosure and any structure which carries it).

3.8.3 Openings in protected shaft

a. A protected shaft shall have no openings in its enclosure, except

(1) in the case of any part of the enclosure which is formed by a separating wall, any opening which complies with the requirements of Cl.3.6 for separating walls, or

(2) in the case of any part of the enclosure which is formed by a  compartment wall or a compartment floor, any opening which complies with the requirements of Cl.3.7 for compartment wall or compartment floor, or

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(3) in the case of any part of the enclosure which is formed by the protecting structure:

(a) a door which has the appropriate fire resistance to comply with the requirements of Cl.3.4 for test of fire resistance, or otherwise permitted by provision of Cl.3.8.6, or

(b) the passage of a pipe, excluding protecting structure to exit staircase and exit passageway, or

(c) inlets to and outlets from and opening for the duct, if the shaft contains or serves as a ventilation duct.

b. Such openings in the protected shaft shall be protected to comply with the relevant provisions of Cl.3.9 for protection of openings.

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3.8.4 Non-combustibility of protecting structures

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Every protecting structure shall be constructed wholly of non-combustible materials except that floor, wall and ceiling finishes which do not contribute to the fire resistance of such protecting structure are not be required to comply with the requirements for non-combustibility.

3.8.5 Ventilation of protected shaft

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Ventilation of protected shaft shall comply with the following:

a. A protected shaft used for the passage of people, such as exit staircases, shall be ventilated to comply with the relevant provisions of the Code.

b. A protected shaft containing a pipe conveying gas shall be adequately ventilated directly to the outside air or have other modes of ventilation allowed under SS 608.

3.8.6 Doors in protecting structures

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a. Any door fitted to an opening in protecting structure shall have fire resistance for not less than half the period required by other provisions of the Code for the protecting structure surrounding the opening.

b. Exception

(1) Any door fitted to an opening in protecting structure of a shaft containing services, such as electrical cables, pipes (including gas pipe in separate shaft), ducts etc., is not required to have the fire resistance rating if the door is located along the wall facing the external corridor.

(2) Any door fitted to an opening in protecting structure of a rubbish chute is not required to have the fire resistance rating if:

(a) the thickness of the metal hopper door is at least 1.5mm;

(b) the hopper door is sealed with rubber gasket; and

(c) the hopper door shall be self-closing type.

3.8.7 Protected shaft containing exit staircase

a. A protected shaft which contains an exit staircase shall not contain any services e.g. pipes, cables, ducts, etc., that are not solely serving the same exit staircase (even if the services are protected with fire-rated dry construction), except for:

(1) cut-off sprinkler and pipe for that staircase;

(2) UPVC or cast iron rain water downpipes serving the roof directly above the exit staircase, and not routed through anywhere outside the staircase; and

(3) rising mains.

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b. The protecting structure shall be constructed of masonry, or drywall. If drywall construction is used, all of the following conditions shall be complied with:

(1) the drywall shall be non-combustible;

(2) the drywall shall have fire resistance rating for not less than the relevant period specified in Table 3.3A having regard to the purpose group of the building of which it forms a part and the dimension specified in that table;

(3) the drywall shall meet the criteria, in terms of impact & deflection performance, when subject to the test of BS 9999 Annex L and BS 5234 Part 2;

(4) the drywall shall meet the criteria, in terms of water absorption and bending strength performance, when subject to the test of BS EN 520 or ISO 1896; 

(5) the drywall shall meet the criteria of Cyclic Loading and Dynamic Test as specified under Building Code of Australia Specification C 1.8; and

(6) the building shall have at least two independent exit staircase shafts (scissors exit staircases are considered single shaft).

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3.8.8 Lift shaft

A protected shaft which contains a lift shall comply with the following:

a. It shall not contain any pipe conveying gas or combustible liquid, other than those in the mechanism of a hydraulic lift.

b. The protecting structure shall be constructed of masonry, or drywall. If drywall construction is used, the conditions stipulated under Cl.3.8.7b.(1) to (6) shall be complied with.

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c. Where a lift is either located at the edge of atrium floors or at the external wall and outside the building, the lift shall be considered as not enclosed within a protected shaft.

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d. The protected shaft shall be vented in accordance with SS 550. The vents shall be so arranged as to induce exhaust ventilation of the shaft. Where vents cannot be provided because of the location of the lift shaft, a ventilation duct protected by drywall complying with Cl.3.8.7b. serving as ventilation of the shaft may be provided instead.  If the duct is not fire-rated, fire dampers shall be provided to the duct at the wall of the lift shaft, provided such relaxation shall not apply to shafts containing a fire lift.

e. Openings for the passage of lift cables into the lift motor room located above or at the bottom of the shaft shall be as small as practicable.

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f. A transom panel above the lift entrance shall be considered as part of the protecting structure and shall therefore conform to the fire resistance requirements of the protected structure.

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g. If it serves any basement storey, it shall be enclosed by  a protected lobby with walls having 1-hr fire resistance rating and fire door of ½-hr fire resistance rating. If the protected lobby also acts as a smoke-free lobby required under Cl.2.2.13, it shall be mechanically ventilated in accordance with Cl.7.1.10.

Exception:

Where the lift landing area is adjoining an air well or external space of minimum clear area 10m² and minimum width of 3m, the distance between the nearest edge of lift door opening to the air well shall not exceed 3m.

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h. Private lift

A private lift that is provided for the exclusive use of occupants in residential buildings under PG II shall comply with all of the following requirements:

(1) A smoke detector shall be provided at the lift landing area. The activation of any of the smoke detectors at the lift landing area shall cause the lift to home to the designated floor.

(2) Emergency power supply from a standby generating plant shall be provided to home the lift to the designated floor when there is a power failure in the building.

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(3) An alternate designated floor (e.g. any other floor with common lobby) shall be identified. The lift shall be brought to the alternate designated floor in the event that there is a fire at the 1st storey designated floor. For buildings without an alternate designated floor, the lift shall return to the last called floor in the event that the designated floor is on fire.

(4) The lift shall not serve as a fire lift.

(5) Private lifts shall comply with SS 550.

R Rationale - Clause 3.8.8h.(3)

This requirement is to ensure that a private lift will not home to the designated floor if it is on fire. For residential buildings having private lifts and are unable to provide an alternate designated floor, the lift control has to be programmed to bring the passengers to a safe floor, normally the last called floor, for egress if the fire is on the designated floor.

3.8.9 Protected shaft containing other services installations

A protected shaft used for the enclosure of services shall comply with the following:

a. The protecting structure for a protected shaft, containing mechanical ventilation ducts serving areas specified in Cl.5.2.1g.(1) and Cl.5.2.1h. or kitchen exhaust ducts, which pass through floor slabs, shall be of masonry construction. Such a shaft shall be completely compartmented from the rest of the shaft space containing other ducts or any other services installations. A protected shaft containing ducts serving other areas which pass through floor slabs can be constructed of drywall. If the protected shaft is of drywall construction, the conditions stipulated in Cl.3.8.7b. shall be complied with.

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b. Cavity barriers

A protected shaft used for the enclosure of electrical power services shall be interrupted at every floor level with at least ½-hr fire resistance cavity barriers. Protected shaft used for the enclosure of telecommunications services shall be interrupted by at least ½-hr fire resistance cavity barriers at vertical intervals not exceeding 15m. The cavity barriers within trunking enclosing electrical and telecommunication cables can be exempted if the following conditions are met:

R Rationale - Clause 3.8.9b

Owing to the difficulty in fire-stopping the gaps within the trunking running through multiple floor levels within a protected shaft, this requirement was exempted provided additional fire safety requirements are complied with. These requirements include the use of flame retardant cables to reduce the possibility of fire from occurring/spreading, sloping of the floor within the shaft upwards at an angle of at least 45° to prevent illegal storage of any combustible materials, and the provision of self-closing devices to the fire resisting doors to ensure that the doors are closed at all times to prevent fire from spreading.

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(1) the cables shall be flame retardant type complying with IEC 60332;

(2) the floor within the shaft shall be sloped upward with an angle of at least 45° to the floor level; and

(3) the fire doors to the protected shaft are installed with self-closing devices.

c. Self-closing devices

Automatic self-closing devices are not required to be installed on fire resisting doors opening into protected shafts which are interrupted by at least ½-hr fire resistance cavity barriers at every floor level, or protected shafts containing sanitary pipes or water pipes, provided that the fire resisting doors are kept closed and locked at all times.

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d. Siting of protected shafts

All protected shafts containing services shall not be located within an exit staircase except for the case of residential apartment/maisonette development under PG II not exceeding 4-storey where smoke-free lobby is not required

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