(1) Grade B construction means construction complying with the particular requirements for this section.

(2) Structural members. – Except as otherwise provided in subsections (3) and (5), all structural members shall have fire-resistance ratings of not less than the ratings specified in Table V.

TABLE V
FIRE_RESISTANCE RATINGS OF STRUCTURAL MEMBERS FOR GRADE B CONSTRUCTION

(3) External walls and external members. – External bearing-walls and non-bearing-walls and external members of structural frames of a building, which are within the distances from the nearest lateral boundary of the stand on which such building is erected or from another building on such stand, specified in column 1 of Table VI, shall have fire-resistance ratings of not less than the corresponding rating specified in column 2 of that Table.

TABLE VI
FIRE-RESISTANCE RATINGS OF EXTERNAL WALLS AND EXTERNAL MEMBERS OF STRUCTURAL FRAMES FOR GRADE B CONSTRUCTION

(4) Covering to the surface of external walls. –

Any covering to the exterior surface of external walls shall be of non-combustible materials:

Provided that timber or other combustible material, to an extent not exceeding 30 per centum of the superficial area of openings formed for show-windows may be used for such openings up to ceiling-level of the ground storey, or to a height of 6 metres above finished ground-level, whichever is the lesser.

(5) Suspended floors. – Suspended floors of timber or other combustible material shall not be permitted except for—

a) The floor of any stage or platform, if the space beneath such floor is not used for storage purposes;

b) Floors on the ground storey of any building, if no part of the space under such floors is used for other than floor-inspection purposes; and

c) Sprung floors if—

i) Such floors are supported on a base having the appropriated fire-resistance rating for suspended floors, as specified in columns 2 and 3 of Table V; and

ii) No portion of such floors is more than 450 millimetres above such base.

(6) Roof assemblies. —Every roof assembly shall have a fire-resistance rating of not less than half an hour.

(7) Combustible material shall not be used as exterior covering to such roof assembly;

Provided that, where the roof construction is of concrete or other non-combustible construction, bituminous felt or other approved combustible material may be used to cover such roof construction.

(8) Every roof-space in a sloping roof having a ceiling shall comply with the relevant requirements of subsections (8) and (9) of section 7.

(9) Partition-walls. –Every partition-wall in a basement shall be of non-combustible material.

(10) Every partition-wall in a storey above the ground storey in auditoria, bowling-alleys, dancehalls, colleges and schools, both residential and non-residential shall be 0f—

a) Non-combustible materials; or

b) Timber or other framing covered on both sides with a material graded as class 1 in the Third Schedule.

(11) All partition-walls, other than those described in subsections (9) and (10), shall be of—

a) Non-combustible materials; or

b) Timber or other framing covered on both sides with a material graded as class 3 in the Third Schedule.

(12) Every doorway in partitions in basements shall be fitted with a fire-door having a fire-resistance rating of not less than half an hour.

(13) Interior trim and finishes. –The use of combustible material shall be permitted for trim to door and window-frames, and for skirtings and chair- and picture-rails, if such trim and finishes are backed solidly with non-combustible material.

(14) Interior wall-linings. – Any interior wall-linings in rooms used for sleeping purposes shall be of material graded as class 1 in the Third Schedule.

(15) Any interior wall-linings, other than linings applied to walls of required exit-ways and of rooms used for sleeping purpose, may be of combustible material, if such walls are of masonry or concrete.