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Legend: Explanations & Illustrations Rationale Note Revision history Print

CLAUSE 3.5 EXTERNAL WALL

3.5.1 Requirements of external walls

The requirements of external walls are as follows:

a. Any external wall of a building or a separated part of a building which constitutes or is situated within a distance of 1m from any point on the relevant boundary, or is a wall of a building or a separated part of a building which exceeds 15m in height shall:

(1) be constructed wholly of non-combustible materials apart from any external wall finishes which complies with Cl.3.5.4 or any internal lining which complies with Cl.3.13.4

(2) be so constructed as to attain the fire resistance required by this chapter; and

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b. any beam or column forming part of an external wall, and any structure carrying an external wall which is required to be constructed of non-combustible material, shall comply with the provisions of Cl.3.5.1a..

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3.5.2 Exceptions on external wall construction

a. The requirements of Cl.3.5.1a.(1) for non-combustibility of external walls need not apply to the external wall of a building or part of a building separated as described in Cl.3.3.2b., if that wall is situated 1m or more from the relevant boundary and it is:

(1) of PG I or II building of not more than three storeys, or

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(2) of single storey construction and not exceeding 15m in height and floor area not exceeding:

(a) 3000m2 for PG III, IV, VII buildings, or

(b) 2000m2 for PG V, VI buildings, or

(c) 500m2 for PG VIII buildings, or

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(3) of other than single storey buildings, but not exceeding 7.5m in height and the compartmented floor area not exceeding:

(a) 250m2 for PG IV, V, VII buildings, or

(b) 150m2 for PG VI, VIII buildings.

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b. The requirements of Cl.3.5.1a.(2) for fire resistance of external walls need not apply to the external wall of a building or part of a building separated as described in Cl.3.3.2b., if that wall is situated 1m or more from the relevant boundary and it is:

(1) of a single storey building of a purpose group other than PG VI and VIII and not exceeding 15m in height, or

(2) of a single storey PG VI or VIII building not exceeding 15m in height and floor area not exceeding 2000m² or 500m² respectively.

3.5.3 Unprotected areas in any side of a building

Unprotected areas in any side of a building shall comply with all of the following:

a. Any relevant requirements relating to the permitted limits of unprotected areas specified in Annex 3B, unless the building is so situated that such side can in accordance with Annex 3B, consist entirely of any unprotected area.

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b. The extent of unprotected openings in an external wall of a building/compartment, in relation to its distance from the lot boundary, can be doubled that of Annex 3B, provided the building/compartment is fitted throughout with an automatic sprinkler system in compliance with the requirements in Chapter 6.

c. As an alternative to Cl.3.5.3b. above, the distance between the external wall of a building and the relevant boundary can be half that specified in Annex 3B, if the building is fitted throughout with an automatic sprinkler system in compliance with the requirements in Chapter 6.

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d. The extent of unprotected openings in an external wall of a building/part of building used for car parking in relation to its distance from the lot boundary/relevant boundary can be based on the floor having the largest extent of unprotected openings to comply with Table 1 of Annex 3B.

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e. Extent of unprotected openings

(1) The extent of unprotected openings in an external wall of a building under PG I, in relation to its distance from the relevant boundary, can be based on the internal room/space in the building that has the largest extent of unprotected openings to comply with Table 1 of Annex 3B.

(2) Internal walls enclosing the room/space in the building are not required to be fire-rated, but shall be constructed of non-combustible materials, except glazing.

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3.5.4 External wall finishes

R Rationale - Clause 3.5.4

This clause stipulates the requirements for cladding materials on the exterior of buildings. It also provides clarity on the rating and classification of that part of the building below 15m in height, and on the use of composite panels as cladding material.

Finishes on external walls shall comply with the following:

a. Homogenous cladding on external walls shall be constructed of material of at least limited combustibility tested in accordance with BS 476 Part 11 or approved equivalent. For buildings not within PG VI and VIII, any part of such cladding below a height of 15m from the ground, and situated at least 1m away from the relevant boundary can consist of:

(1) timber of not less than 9mm finished thickness, or

(2) a material having a surface which achieves at least:

(a) Class 0 flame-spread rating tested in accordance with BS 476 Part 6 & 7, or

(b) Class B rating classified under EN 13501-1.

b. Composite panels used as cladding on external walls shall comply with Cl.3.15.13.

3.5.5 Reference to Part I & II of Annex 3B

Any reference to Annex 3B shall be construed as referring to the provisions of Part I of that Annex together with the provisions of Part II.

3.5.6 Buildings on land in common occupation

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If two or more detached buildings are erected on land in common occupation, for any external wall of such a building facing the external wall of an adjacent building, the relevant boundary shall be a notional boundary passing between those buildings. This notional boundary shall be positioned to enable the external walls of those buildings to comply with the requirements of Cl.3.5.3.

3.5.7 Vertical fire spread

R Rationale - Clause 3.5.7

The purpose of providing high/low separation is to ensure fire will not spread from the lower compartment to the abutting higher different compartment of the building.

a. For high and low parts of different compartments of a building abutting each other, either one of the following requirements shall be complied with to prevent spread of fire between the distinct parts:

(1) the roof-over of the lower part of the building shall be fire-rated in accordance with the element of structure for minimum 1 hr for a distance of 5m measured horizontally from the external wall of the higher part of building; or

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(2) the external wall of the higher part of the building overlooking the roof below shall have the necessary fire resistance rating in accordance with the element of structure for minimum 1 hr for a vertical height of not less than 9m measured from the roof of the lower part of the building.

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b. The above requirements shall not be applicable to:

(1) buildings or lower parts of the building which are sprinkler-protected;

(2) the buildings under the conservation programme of the authority having jurisdiction, or buildings built before 1969;

(3) covered car porches intended solely for the purpose of the boarding and alighting of passengers;

(4) open-sided/covered walkways/linkways not exceeding 5m in width with no commercial activities or storage; and

(5) canopies of dept not exceeding 2m over private enclosed spaces or balconies in PG II buildings, provided that the canopy is constructed of non-combustible material.

3.5.8 Non-sprinkler-protected roof

R Rationale - Clause 3.5.8

This fire safety requirement is to prevent fire from spreading through an unprotected roof to an adjacent building located outside the boundary.

The 4m setback stipulated is consistent with the minimum horizontal 5m protection required under Cl.3.5.7a.(1) to prevent vertical fire spread, taking into consideration a minimum 1m setback of the adjacent building from the boundary.

For non-sprinkler-protected roof within 4m from the boundary (excluding boundary abutting public street, canal or river), the portion of the roof within this 4m zone shall be 1-hr fire-rated. This requirement is exempted for areas mentioned under Cl.3.5.7b..

3.5.9 Separation of residential floor facade

R Rationale - Clause 3.5.9

The fire-rated spandrel and horizontal projection from building facade are to serve as an effective fire barrier to slow down or prevent vertical fire spread. The dimensions have been validated through a fire engineering study.

The façade of residential floors above 24m habitable height shall be separated from each other by:

a. a 1-hr fire-rated spandrel of at least 1.5m in height, or

b. a 1-hr fire-rated horizontal projection that extends at least 600mm from the building.

3.5.10 External sun-breakers/weather features

External sun-breakers or weather features which will result in the channelling of flame upwards during a fire are not permitted.