Wood or other combustible material may be used
in the construction or interior finish of Class 1 Fireproof Structures
and Class 2 Fire-Protected Structures only as hereafter provided.
A. Floor sleepers, bucks, nailing blocks and grounds.
Floor sleepers, bucks, nailing blocks and grounds, if only the railing
surface is exposed, may be of wood in Class 1 Fireproof Structures
and Class 2 Fire-Protected Structures. When floor sleepers of combustible
material are used, the space between the floor construction and the
wood flooring shall be filled with incombustible material, except
that in Class 2 Fire-Protected Structures, combustible floor sleepers
may be used without filling in such space, provided that such floors
are fire-stopped at the girder lines in areas of 400 square feet or
less and under all permanent partitions.
B. Interior trim. Wood flooring, interior doors, sash with their frames, trim and casings, other interior wood and other approved combustible trim, when backed solidly with fire-resistive material, may be used as provided in §
86-96, Construction of special occupancy structures, and §
86-97, Construction of stage and proscenium wall, and elsewhere than in stair enclosures, public hallways and passageways in Class 1 Fireproof Structures, 150 feet or less in height, and Class 2 Fire-Protected Structures.
C. Wearing surfaces.
(1) Wearing surfaces 1/2 inch or less in thickness made
of cork or rubber composition, linoleum, asphalt composition tile
or similar material having the same fire-resistive qualities when
cemented to the upper surface of an approved type of fire-resistive
floor construction may be used elsewhere than in stair enclosures.
Where wood flooring is permitted, such wearing surfaces may be cemented
directly to the wood floor.
(2) Untreated wood finish flooring 7/8 inch or less in
aggregate thickness, when cemented or attached directly to the surface
of an approved type of fire-resistive floor construction, may be used
elsewhere than in stair enclosures and corridors, and in structures
exceeding 150 feet in height, a wood subflooring may be used to support
such combustible finish flooring or a wearing surface as permitted
in the preceding paragraph, provided that such subflooring and the
sleepers supporting it shall be treated to render them fire-resistive
in accordance with the rules of the Superintendent of Buildings.
(3) Untreated combustible insulation board, in a single
layer not to exceed 1/2 inch in thickness when cemented or attached
directly to the surface of an approved type of fire-resistive floor
construction, may be used elsewhere than in stair enclosures and corridors
when covered by an incombustible wearing surface in accordance with
the rules of the Superintendent of Buildings.
D. Subdividing partitions. Subdividing partitions in Class l Fireproof Structures and Class 2 Fire-Protected Structures shall be made of incombustible material or wood or other approved combustible material treated to render it fireresistive, except that partitions made of a single thickness of wood or wood and glass may be used in Class 1 Fireproof Structures, 150 feet or less in height, and Class 2 Fire-Protected Structures to subdivide rooms or spaces 5,000 square feet or less in area, except as provided in §
86-72F, Fire-proof structures, one-hour, if separated from adjoining rooms or spaces, corridors, elevator and stair enclosures by fireproof partitions or walls made of incombustible material having a fire-resistive rating of at least one hour.
E. Use of treated wood for fire protection.
(1) Wood flooring treated to render it fire-resistive
in accordance with the rules of the Superintendent of Buildings may
be used elsewhere than in stairs, halls and corridors.
(2) Wood window sash, frames and trim treated to render them fire-resistive may be used elsewhere than in stair halls and corridors, except for exterior windows where otherwise provided in §
86-74, Protection of exterior openings.
(3) Wood treated to render it fire-resistive may be used
for other interior trim elsewhere than in stair halls or in corridors.
(4) Wooden doors with their frames and trim treated or
protected to render them fire-resistive may be used in any location,
provided that they meet the fire-resistive requirements for such location.
F. Freestanding molding and veneers. Untreated wood may
be used, except in stair halls and required exit corridors, for freestanding
moldings having a cross-sectional area of two square inches or less
and for face veneers, 1/8 inch or less in total or aggregate thickness
and glued to treated cores or backing. Untreated wood veneers, 1/20
inch or less in thickness when mounted directly upon incombustible
material, may be used without restriction as to location.