A.
Classification and use.
(1)
Fire-resistive materials shall be classified on a
time and temperature basis and used in accordance with the requirements
of this code and the rules of the Superintendent of Buildings.
(2)
The requirements of this article are intended to provide
adequate protection against fire and shall not be considered to waive
any requirements of other sections of this code for stronger construction
in order to provide safe load carrying capacity.
B.
Fire-resistive construction details.
(1)
Fire-resistive units of burnt clay or shale, sand-lime,
concrete or gypsum shall be laid up in cement mortar, cement-lime
mortar or gypsum mortar for gypsum units.
(2)
Units shall be solidly bedded and shall be thoroughly
bonded by broken joints in alternate courses or by approved metal
ties.
(4)
Poured in place concrete or gypsum fire-resistive
materials for protective purposes shall be reinforced with a sufficient
amount of metal bars or mesh to ensure the integrity of the construction.
(5)
Plaster used in fire-resistive construction shall
consist of gypsum or cement mortar or other equally fire-resistive
material.
C.
Spaces exterior to structures.
(1)
Any space within the grade story in a structure may
be considered exterior to the structure, provided that it is cut off
from the structure on all sides adjacent thereto by walls having a
fire-resistive rating of at least four hours and access to such space
is from the outside only.
(2)
Any area of a grade story of a structure without exterior
walls and cut off from the remainder of the structure by partitions
or walls having a fire-resistive rating of at least four hours may
be considered as outside of the structure.
D.
Test for fire-resistive materials. Other materials, appliances or methods of construction for fire-resistive purposes not specifically provided for in this code shall, on written application to the Superintendent of Buildings, be tested in accordance with Subsection F of this section and, if found to comply with the requirements of this code, they shall be approved by the Superintendent of Buildings.
E.
Thickness and fire-resistive ratings for protection
of structural steel. Unless otherwise determined by test in accordance
with the rules of the Board, the thicknesses of fire-resistive materials
in this table, exclusive of airspaces when used for the protection
of structural steel members, shall be assumed to have the following
fire-resistive ratings. Such thicknesses are the minimum permissible
and their reduction for the embedment of pipes, conduits or wires
or for any other purpose is forbidden.
|
Hours
| |||||
|---|---|---|---|---|---|
|
Inches of
|
One
|
Two
|
Three
|
Four
| |
|
Brick (burned clay or shale)
|
2 1/4
|
2 1/4
|
3 3/4
|
3 3/4
| |
|
Brick (sand-lime)
|
2 1/4
|
2 1/4
|
3 3/4
|
3 3/4
| |
|
Concrete brick, block or title, except cinder
concrete units
|
2 1/4
|
2 1/4
|
3 3/4
|
3 3/4
| |
|
Hollow or solid cinder concrete block and tile
having a compressive strength of at least 700 pounds per square inch
of gross area
|
1 1/2
|
2
|
2
|
2 1/2
| |
|
Solid gypsum block, provided that to obtain the four-hour rating, such blocks shall be plastered with at least 1/2 inch of gypsum plaster (See Subsection C)
|
1
|
1 1/2
|
2
| ||
|
Gypsum poured in place and reinforced
|
1
|
1 1/2
|
1 1/2
|
2
| |
|
Hollow or solid burned clay tile or combinations of tile and concrete (See Subsection C)
|
1 1/2
|
2
|
2
|
2 1/2
| |
|
Metal lath and gypsum plaster (See Subsection B)
|
7/8
|
1 1/2
|
2
|
2 1/2
| |
|
Cement concrete, Grade I (See Subsection A)
|
1
|
1 1/2
|
2
|
2
| |
|
Cement concrete, Grade II (See Subsection A)
|
1 1/2
|
2
|
3
|
4
| |
|
Cement concrete, Grade II with wire mesh (See Subsection D)
|
1 1/2
|
2
|
2
|
3
| |
|
Hollow gypsum block, provided that to obtain
the four-hour rating, such blocks shall be plastered with at least
1/2 inch of gypsum on outer side
|
3
|
3
|
3
|
3
| |
(1)
Concrete grades and aggregates. Grade I concrete is
concrete in which the aggregate consists of limestone, traprock, blast
furnace slag, cinders or calcareous gravel. Grade II concrete is concrete
in which the aggregate consists of granite or siliceous gravel.
(2)
Plaster equivalents. One-half inch of unsanded gypsum
plaster shall be taken as the equivalent of 3/4 inch of sanded gypsum
or cement plaster. Plaster protections more than one inch in thickness
shall have an additional layer of metal lath embedded 3/4 inch or
less from the outer surface and securely tied to the protected member.
The thickness of the plaster shall be the minimum thickness of plaster
measured from the face of the lath or of the masonry.
(3)
Anchors, bonds and ties. Metal anchors, bonds or caging shall be used with solid sypsum block and cement concrete. For gypsum block protections for all periods and for other block or tile protections for periods of over two hours, metal anchors in the horizontal joints shall be used. Hollow gypsum shall be anchored with U-straps placed between the blocks and running into the hollow spaces. For Grade I or Grade II concrete or poured gypsum, the ties shall consist of wire mesh complying with Subsection E(4) or the equivalent in metal ties or spirally wound wire.
(4)
Wire mesh. Wire mesh for tying concrete projections
shall weigh at least 1 1/2 pounds per square yard and shall be
of a type approved by the Superintendent of Buildings.
F.
Fire tests, unless otherwise provided for under rules.
All materials and assemblies shall be tested in accordance with the
rules promulgated by the Superintendent of Buildings and approved
by the Board of Trustees. In the absence of such rules, all materials
and assemblies shall be tested in accordance with the standard fire
test formulated under the auspices of the American Standards Association
or the standard fire test specifications of the American Society for
Testing Materials, D, C19-26T, and the results shall be expressed
in time periods of resistance, as for example, four-hour, one-half-hour,
etc.
A.
Protection of columns.
(1)
Iron or steel columns shall be protected by material
or assemblies having a fire-resistive rating of four hours for Class
1 Fireproof Structures and of three hours for Class 2 Fire-Protected
Structures, except that interior columns in Class 2 Fire-Protected
Structures for residence purposes may have only two-hour protection.
(2)
Special precautions shall be taken to protect the
outer surfaces of iron or steel columns located in exterior walls
against corrosion by painting with waterproof paints, by the use of
mastic or by other methods of waterproofing approved by the Superintendent
of Buildings.
B.
Protection of lugs, brackets and wind bracing. Where
the column is solidly encased with fire-resistive material, the extreme
outer edge of lugs, brackets, wind bracing or other supporting parts
may extend to within one inch of the outer surface of the protection.
C.
Protection of fire-resistive covering. Where the fire-resistive
covering on columns is exposed to injury from moving vehicles or the
handling of merchandise, it shall be jacketed to a height of five
feet from the floor with an adequate protective covering.
D.
Protection of wall girders and other steel supporting
masonry. Wall girders and other steel supporting masonry shall be
protected by material or assemblies having a fire-resistive rating
of three hours.
E.
Protection of beams and girders.
(1)
Beams and girders supporting floor or roof construction
in Class 1 Fireproof Structures shall be individually encased with
materials or assemblies having a three-hour fire-resistive rating,
except that in areas of 500 square feet or less, secondary beams may
be protected by a suspended ceiling with a three-hour fire-resistive
rating, provided that such areas are completely fire-stopped, and
that where such ceilings extend into the web of the main girders,
the fireproofing of such girders may also be omitted above the ceiling
if the girder webs are solid.
(2)
Beams and girders supporting floor and roof construction
in Class 2 Fire-Protected Structures shall be individually encased
with materials or assemblies having a one-and-one-half-hour fire-resistive
rating, except that in areas of 500 square feet or less, secondary
beams may be protected by a suspended ceiling with a one-and-one-half-hour
fire-resistive rating, provided that such areas are completely fire-stopped,
and that where such ceilings extend into the web of the main girders,
the fireproofing of such girders may also be omitted above the ceiling
if the girder webs are solid, and except that the floor above the
cellar or basement shall have a fire-resistive rating of at least
three hours.
(3)
Firestopping, as required in this section, shall be
done with materials or assemblies having the same fire-resistive rating
as the fireproofing.
F.
Protective of lintels.
(1)
In Class 1 Fireproof Structures, iron or steel lintels
over openings more than four feet wide in walls shall be protected
as required for wall girders, unless the lintel is supported from
a fireproof member above, provided that when the span of any such
opening is six feet or less and such opening is spanned by an adequate
masonry arch above the lintel, the protective covering may be omitted.
(2)
In Class 2 Fire-Protected Structures, iron or steel
lintels over openings more than six feet wide in walls shall be protected
as required for wall girders, unless the lintel is supported from
a fireproof member above, provided that when the span of any such
opening is eight feet or less and such opening is spanned by an adequate
masonry arch above the lintel, the protective covering may be omitted.
(3)
In Class 3 Nonfireproof Structures of two stories
or more in height, iron or steel lintels over openings more than eight
feet wide in walls shall be protected as required for wall girders,
unless the lintel is supported from a fireproof member above.
G.
Use of stone lintels restricted. The use of stone
lintels is forbidden unless supplemented on the inside of the wall
with iron or steel lintels or with suitable masonry arches carrying
the masonry backing or by other methods if approved by the Superintendent
of Buildings.
H.
Protection of trusses.
(1)
Trusses in Class 1 Fireproof Structures and Class
2 Fire-protected Structures shall be entirely protected by material
or assemblies having fire-resistive ratings of three hours and 1 1/2
hours, respectively. The protective covering may be omitted from members
of trusses, including beam and subpurlins, in one-story structures
and in multistory structures when supporting only roof loads, access
passageways or ventilating equipment and having a clear height of
at least 20 feet below the lower chords of the trusses.
(2)
The protective covering may be omitted from roof truss
members, including beams and subpurlins, if a continuous ceiling having
a fire-resistive rating of three hours is provided below the lower
chords of the trusses and the space above the ceiling is completely
enclosed and fire-stopped and contains no passageways or apparatus
of any kind. Access to the enclosed roof space shall be permitted
by an access door having a fire-resistive rating of at least one hour
and having maximum dimensions of three feet by three feet.
A.
Form and fire-resistive ratings of floor and roof
construction.
(1)
Floor and roof construction between supporting beams
in Class 1 Fireproof Structures shall consist of arches or slabs of
incombustible material or assemblies and shall, either by itself or
in combination with its protective ceiling, have a fire-resistive
rating of at least three hours, except as specifically provided otherwise.
Nothing in this section shall prevent the application of cork or fiber
insulation board applied directly to the fire-resistive floor or roof
construction, in cement, provided that such insulation is covered
by at least a one-and-one-half-inch thickness of portland cement concrete
or other equally fire-resistive material of equal thickness. Similar
floor and roof construction in Class 2 Fire-Protected Structures shall,
either by itself or in combination with its protective ceiling, have
a fire-resistive rating of at least 1 1/2 hours, except as otherwise
specifically provided.
(2)
Where the fire-protective covering is omitted from roof trusses, as provided in § 86-70H, Protection of trusses, blocks of book tile, gypsum, concrete or other equivalent fire-resistive materials may be used for horizontal or sloping roofs directly above such trusses, provided that the necessary strength requirements are met.
B.
Concrete floor and roof construction.
(1)
Minimum proportions for stone and cinder concrete. Unless designed in accordance with the provisions of § 86-61, Reinforced concrete, concrete floor and roof construction shall consist of a mixture of one part of cement by volume, two parts of sand by volume and a maximum of five parts of coarse aggregate measured separately by volume and reinforced with steel as provided in Subsection B(4), Strength of concrete floor and roof construction. Cinder aggregate shall be clean and well-burned and shall contain a maximum of 35% by weight of unconsumed carbon and 1 1/2% by weight of sulfur. Other aggregates shall conform to § 86-47D(1), Aggregates.
(2)
Reinforcements to concrete floor and roof construction.
Reinforcement shall consist of steel fabric, rods or other suitable
shapes. The reinforcement shall be at least 0.015% for continuous
steel fabric and at least 0.025% for other forms of steel reinforcement,
the percentage to be based on the sectional area of the slab above
the center of reinforcement. The center of the reinforcement shall
be at least one inch above the bottom of the slab, but all parts of
the reinforcement shall be at least 3/4 inch from the bottom of the
slab.
(3)
Thickness of concrete floor and roof construction. Unless designed in accordance with the provisions of § 86-61, Reinforced concrete, the minimum thickness of concrete floor and roof construction shall be determined by the following formula:
.tif.png) | |
|
where
| |
|
t = total thickness in inches.
| |
|
L = span in feet between steel flanges.
| |
|
w = gross uniform load in pounds per square
foot.
| |
|
But t shall be at least four inches with the
following two exceptions:
|
(a)
Special forms of construction which have passed a three-hour fire test as specified in § 86-69F.
(b)
In Class 2 Fire-Protected Structures, floor construction, except the floor construction above the cellar or basement, and roof construction may be used consisting of two inches or more of reinforced concrete or gypsum top slab or two inches or more of stone or cinder concrete poured over rib lath and secured to the top of steel beams or steel joists and at least a seven-eighths-inch gypsum or cement plaster ceiling on metal lath or any other material or assembly having a fire-resistive rating of at least 1 1/2 hours. (See also § 86-13B, Class 2 Fire-Protected Structures, and § 86-76A, Floor sleepers, bucks, nailing blocks and grounds.) Four-inch slabs may be used for spans of eight feet or less, provided that the gross floor load is 200 pounds per square foot or less.
(4)
Strength of concrete floor and roof construction.
(a)
Unless designed in accordance with § 86-61, Reinforced concrete, the safe carrying capacity of concrete floor and roof construction shall be determined by the following formula:
(a).tif.png) | |
|
where
| |
|
w = gross uniform floor load in pounds per square
foot.
| |
|
As = cross-sectional area of reinforcement in
square inches per foot of width of slab.
| |
|
L = clear span, in feet, between steel flanges
and shall not exceed 10 feet in any case, and when the gross floor
load exceeds 200 pounds per square foot, the span shall not exceed
eight feet.
| |
|
C = the following coefficient for steel having
an ultimate strength of at least 55,000 pounds per square inch:
| |
|
For cinder concrete:
| |
|
Twenty thousand when reinforcement is continuous.
| |
|
Fourteen thousand when reinforcement is hooked
or attached to one or both supports.
| |
|
For stone concrete:
| |
|
Fifteen thousand when reinforcement is hooked
or attached to one or both supports.
| |
|
Twenty-three thousand when reinforcement is
continuous.
|
(b)
The use of this formula is forbidden unless
the reinforcement is hooked or attached to one or both supports or
is continuous and the slab is stone or cinder binder concrete at least
four inches in thickness.
(c)
The concrete in such floor and roof construction
shall have an ultimate compressive strength of at least 700 pounds
per square inch at the end of 28 days. For such concrete, the safe
fiber stress may be taken as 200 pounds per square inch, the bond
at 50 pounds per square inch and n equals 30, and the strength may
be figured by the usual methods.
(d)
If steel of an ultimate strength in excess of
55,000 pounds per square inch is used, the above coefficient may be
increased in the ratio of the ultimate strength to 55,000 but at most
30%, provided that a certificate of the manufacturer, certifying to
the minimum strength of the wire fabric actually to be used, is submitted
before erection.
C.
Gypsum floor and roof construction. Gypsum floor and roof construction may be either of reinforced poured gypsum or precast units and may be either of the suspension type or of the slab and ceiling type with the slabs constructed of such thickness as to support the imposed loads, provided that the floor or roof construction complies with the requirements of Subsection A, Form and fire-resistive ratings of floor and roof construction.
D.
Hollow tile arches.
(1)
Material for hollow tile arches. Hollow blocks of
burnt clay or shale used in hollow tile arches for fire-resistive
construction shall be medium or hard and of uniform density. Shells
and webs shall be at least 5/8 inch thick. The maximum spacing of
interior vertical and horizontal webs shall be four inches. The blocks
shall have at least two cells in depth and shall be laid in cement
mortar and be properly keyed.
(2)
Depth of flat arches. The depth of flat arches of
burnt clay or shale hollow blocks shall be at least 1 1/2 inches
for each foot of span, exclusive of the portion of the block extending
below the underside of the beam, with a minimum thickness of six inches.
E.
Brick arches. Brick arches shall be built of common
or hollow brick solidly bonded. They shall be segmental in form with
a minimum thickness of four inches for spans of five feet or less
and of eight inches for spans exceeding five feet unless suitably
reinforced. The rise of such arches shall be at least one inch per
foot of span, and the joints shall be filled with cement.
F.
Rise of segmental arches. Segmental arches for floor
and roof construction shall have a rise of at least one inch per foot
of span. The minimum thickness of this type of arch shall be six inches.
G.
Special roof construction. For mansards and dormers having a slope of more than 30° from the horizontal blocks of book tile, gypsum, concrete or other fire-resistive materials may be used subject to the load test specified in Subsection H, Load tests for floor and roof construction, and provided that they have a fire-resistive rating of at least one hour.
H.
Load tests for floor and roof construction. When the
strength of any floor or roof construction cannot be determined by
the methods prescribed in this section or by the application of accepted
engineering formulas, the safe uniformly distributed carrying capacity
shall be taken as a fraction of the total load causing failure in
a full-sized test sample when applied along two lines, each distant
1/3 of the span from the supports. This fraction shall be 1/4 when
the specimens are tested as simple spans and 1/6 when tested as continuous
spans.
I.
Span of floor and roof construction. Unless designed in accordance with § 86-61, Reinforced concrete, the maximum clear span for floor and roof slabs or arches between supporting beams shall be eight feet, except as otherwise permitted by Subsection B(4), Strength of concrete floor and roof construction.
J.
Openings in floors and roofs. Suitable metal framing or reinforcement shall be provided in fire-resistive floor and roof construction around any opening having an area in excess of two square feet. When openings are provided for pipes and conduits, the unoccupied space shall be filled with approved incombustible material for the full depth of the slab unless close fitting individual sleeves, solidly embedded in the construction, are used or the opening is enclosed as a shaft and constructed in compliance with § 86-73A, Protection of closed shafts.
K.
Tie-rods. The supporting beams in fire-resistive floors
and roofs shall be tied together by steel tie-rods of proper size,
spacing and location, provided that when the floor filling is in the
form of reinforced slabs and the reinforcement is continuous over
the supports or securely attached to the supports, tie-rods may be
omitted.
L.
Top filling. In Class 1 Fireproof Structures, the
space between the floor slab and the finished floor shall be filled
with concrete consisting of one part of cement to a maximum of 10
parts of cinders or with other incombustible material approved by
the Superintendent of Buildings.
A.
Materials and thicknesses of fire walls, four-hour.
(1)
Fire walls shall be constructed of the following materials
and minimum thicknesses, exclusive of any required plaster:
(a)
Solid brick, solid structural units or plain
concrete eight inches thick.
(b)
Solid reinforced concrete six inches thick.
(c)
Solid cinder concrete blocks eight inches thick.
(d)
Solid cinder concrete blocks six inches thick
and plastered on both sides.
(e)
Hollow clay tile 12 inches thick, two units
and three cells in wall thickness.
(f)
Hollow clay tile eight inches thick, three cells
in wall thickness and plastered on both sides.
(g)
Hollow concrete blocks (one piece) 12 inches
thick, webs and shells to be at least 1 1/2 inches thick and
at least two cells in wall thickness.
(h)
Hollow concrete blocks (one piece) eight inches
thick, plastered on both sides, and shells to be at least 1 1/2
inches thick.
(2)
Fire walls of other materials or forms of construction
shall have a fire-resistive rating of four hours.
B.
Construction of fire walls.
(1)
Fire walls shall be constructed with solid joints
of cement or cement-lime mortar. Where plaster is required, unsanded
gypsum plaster shall be at least 1/2 inch thick and sanded gypsum
or cement plaster shall be 3/4 inch thick.
(2)
In a Class 2 Fire-Protected Structure or a Class 3
Nonfireproof Structure, a fire wall shall be continuous from its foundation
to three feet above the roof surface, except as provided in the following
paragraph, and except that in residence structures of these two classes,
fire walls may be carried only to the underside of the roof in Class
2 Fire-Protected Structures and only to the underside of the roof
boards in Class 3 Nonfireproof Structures, provided that the junction
between the roof and the fire wall is thoroughly fire-stopped.
(3)
Fire walls may be offset from floor to floor in any
structure, provided that the entire offset is of fire-resistive construction
having a fire-resistive rating of four hours.
(4)
Combustible structural members built into a solid
fire wall shall be separated from each other and from the outside
of the wall by at least four inches of solid masonry.
(5)
When combustible members project into hollow fire
walls, the hollow space shall be filled solidly with incombustible
fire-resistive materials for the full thickness of the wall and for
four inches or more above, below and between the members.
(6)
Fire walls of masonry used as party or bearing walls shall conform in thickness and material to the requirements for such walls as specified in § 86-60, Masonry construction.
(7)
The application of cork or fiber insulation board
may be permitted if cemented or attached directly to the face of the
wall, laid up with no intervening airspaces and protected as required
by the rules of the Superintendent of Buildings.
C.
Materials for fire partitions, three-hour.
(1)
Fire partitions shall be constructed of the following
materials and minimum thicknesses, exclusive of any required plaster:
(a)
Solid brick, solid structural units or plain
concrete eight inches thick.
(b)
Solid reinforced concrete five inches thick.
(c)
Solid cinder concrete blocks six inches thick.
(d)
Hollow clay tile, two cells in wall thickness,
six inches thick and plastered on the room side.
(e)
Hollow concrete block eight inches thick, provided
that calcareous, burnt clay or cinder aggregates are used and the
shells are at least 1 1/2 inches thick if unplastered and at
least one and 1/4 inches thick if plastered.
(f)
Hollow gypsum block four inches thick and plastered
on both sides.
(g)
Hollow gypsum block six inches and two cells
in wall thickness and plastered on one side.
(2)
Where combustible insulation board is permitted, it
shall be applied directly to the face of the partition by cement or
other approved method, but in no case shall it be built into the required
partition construction.
(3)
Fire partitions of other materials or forms of construction
shall have a fire-resistive rating of three hours.
D.
Construction of fire partitions.
(1)
The maximum unsupported height of a fire partition shall be 30 times its total thickness unless suitably anchored and reinforced or constructed in accordance with the requirements for walls as specified in § 86-60, Masonry construction. Intermediate support for fire partitions shall be of construction having a fire-resistive rating of three hours. Fire partitions may be offset from floor to floor in any structure, provided that the entire offset is of fireproof construction having a fire-resistive rating of three hours.
(2)
Combustible structural members built into a fire partition
wall shall be separated from each other and from the outside of the
wall by at least four inches of solid masonry.
(3)
Where combustible insulating boards are permitted
on a fireproof partition, they shall be cemented or directly attached
to the face of the partition and may not be built into the required
construction.
E.
Fire-resistive stairway enclosures, two-hour.
(1)
Fire-resistive stairway enclosures constructed of
the following materials and minimum thicknesses, exclusive of any
required plaster, may be used in Class Fireproof Structures, exclusively
for school purposes, and in Class 2 Fire-Protected Structures:
(a)
Solid brick or solid structural units eight
inches thick.
(b)
Solid concrete, plain or reinforced, four inches
thick.
(c)
Solid cinder concrete blocks four inches thick
and plastered on both sides three inches thick.
(d)
Solid gypsum, poured or block, three inches
thick.
(e)
Hollow clay tile, two cells in wall thickness,
four inches thick and plastered on both sides or six-inch partition
tile, two cells in wall thickness and plastered on one side.
(f)
Hollow concrete block eight inches thick or
four inches thick and plastered on both sides.
(g)
Hollow gypsum block three inches thick and plastered
on both sides.
(2)
Fire-resistive stairway enclosures of other materials
or forms of construction shall have a fire-resistive rating of at
least two hours.
F.
Fireproof partitions, one-hour.
(1)
Fireproof partitions shall be constructed of the following
materials and minimum thicknesses, exclusive of any required plaster:
(a)
Solid or hollow brick or solid structural units
four inches thick.
(b)
Solid gypsum, poured or block, two inches thick.
(c)
Solid cinder concrete, poured or block, three
inches thick.
(d)
Solid walls of cement mortar or concrete 2 1/2
inches thick and reinforced in two directions with at least 1/8 of
1% of steel in each direction.
(e)
Solid walls at least 2 1/2 inches thick
of gypsum or cement plaster and supported by incombustible studding
and metal lath or mesh.
(f)
Hollow clay tile three inches thick and plastered
on both sides.
(g)
Hollow gypsum blocks three inches thick.
(h)
Hollow concrete blocks three inches thick and
plastered on both sides.
(i)
Hollow walls of gypsum board at least 1/2 inch
thick on incombustible studding three inches thick and plastered on
both sides with 1/2 inch of unsanded gypsum plaster.
(j)
Hollow partitions of metal lath or mesh or welded
wire ribbed lath and plaster on incombustible studding with 3/4 inch
of cement or gypsum plaster on each side. When paper-backed lath is
used, the paper shall be flameproof.
(k)
Hollow walls, at least three inches thick, of
gypsum board, at least 1/2 inch thick, on both sides of incombustible
studding spaced not over 16 inches on centers and covered on both
sides with one-eighth-inch-thick hard asbestos cement composition
sheets with all joints covered with two-inch-wide batten strips of
the same material as sheets or of approved type metal strips.
(2)
In nonfireproof structures, wood-stud fire-retarding partitions may be used as fireproof partitions with a maximum spacing of 16 inches on centers and metal lath or mesh weighing at least three pounds per square yard fastened to the studding at maximum intervals of six inches vertically and plastered on both sides with gypsum or cement plaster to at least three-fourths-inch grounds, or three-eighths-inch plasterboard on both sides plastered with 1/2 inch of unsanded gypsum plaster, or one-half-inch plasterboard on both sides covered with hard asbestos cement composition sheets at least 1/8 inch in thickness with all joints covered with two-inch batten strips of the same material or with approved metal battens. Grounds for chair rails, baseboards and similar appurtenances, if used in such partitions, shall be of metal-covered wood or of incombustible material. Continuous vertical spaces in such walls shall be fire-stopped as required in § 86-80, Firestopping. Spaces between studs shall be filled with incombustible material when required by the Superintendent of Buildings.
(3)
Fire partitions of other materials or forms of construction
shall have a fire-resistive rating of one hour.
G.
Construction of fireproof partitions.
(1)
Fireproof partitions in Class 1 Fireproof Structures
and Class 2 Fire-Protected Structures shall be carried at each tier
of a structure on incombustible supports and, unless suitably anchored
or reinforced, the maximum unsupported height shall be 30 times the
total thickness.
(2)
Where plaster is required, unsanded gypsum plaster
shall be at least 1/2 inch thick and sanded gypsum or cement plaster
shall be 3/4 inch thick.
A.
Protection of closed shafts.
(1)
A series of floor openings consisting of two or more
openings in successive floors or a floor and a roof shall be deemed
to be a shaft and shall be enclosed.
B.
Protection of elevator shafts in existing structures.
(1)
Shafts for elevators, escalators or similar hoisting devices in existing Class 3 or Class 4 public structures, as defined in § 86-12A(1), Public buildings, which are not already enclosed with fire-resistive materials shall be enclosed as provided in Subsection A, Protection of closed shafts, except as otherwise herein provided in Subsection J, Existing shaftways.
C.
Protection of vent shafts in nonfireproof residence
structures. In nonfireproof residence structures occupied by one or
two families, vent shafts shall be supported on and be constructed
of materials having a fire-resistive rating of one hour and shall
extend at least three feet above the roof and be covered by a ventilating
skylight of metal and glass.
D.
Enclosure at the top of shafts. In nonfireproof structures,
except one- and two-family residence structures, shafts extending
into the top story shall be carried through and at least three feet
above the roof. Every shaft extending above the roof, except open
shafts and elevator shafts, shall be enclosed at the top with a roof
of materials having a fire-resistive rating of three hours and shall
have a metal skylight covering at least 3/4 of the area of the shaft
in the top story, except that the required skylight may be replaced
by a window or windows of equivalent area in the side of the shaft,
provided that the sills of such windows are at least three feet above
the roof and that the windows do not face within 10 feet of a property
line. Any shaft terminating below the top story of a structure shall
have the top enclosed with material having a fire-resistive rating
of three hours.
E.
Enclosure of the bottom of shafts. The bottom of shafts
which do not extend to the ground, except vent shafts, shall be enclosed
with materials having a fire-resistive rating of three hours elsewhere
than in one- or two-family residence structures.
F.
Enclosure for hoisting machinery. Any compartment
containing machinery which communicates with a shaft enclosure shall
have its enclosing walls constructed of materials or assemblies having
at least the same fire-resistive rating as the shaft enclosure with
which it communicates.
G.
Number of elevators in a shaft. Not more than two
elevators shall be placed hereafter in any one shaft, and where there
are only two elevators in any building, they shall be placed in separate
shafts.
H.
Enclosure of open shafts. Open shafts shall be enclosed
with materials having a fire-resistive rating as required for exterior
walls or of any other form of construction having a fire-resistive
rating of three hours and possessing proper weatherproof qualities.
I.
Dumbwaiter shafts. Dumbwaiter shafts in residence
structures and having a cross-sectional area of nine square feet or
less shall have a fire-resistive rating of at least one hour for shafts
extending not more than three stories or 40 feet above the basement
or cellar and a fire-resistive rating of at least two hours for shafts
extending more than three stories or 40 feet but not more than six
stories or 75 feet above the basement or cellar, except that any part
of such dumbwaiter shafts which extend into the cellar or basement
shall be protected by materials or assemblies having a fire-resistive
rating of at least three hours.
J.
Existing shaftways.
(1)
Any existing hoistway, elevator or wellhole not already
enclosed, as provided in this code, and not provided with fireproof
doors, the opening thereof through and upon each floor of said building
shall be provided with and protected by substantial guards or gates
and with such good and sufficient trapdoors as may be directed and
approved by the Superintendent of Buildings. When, in the opinion
of the Superintendent, automatic trapdoors are required to the floor
openings of any unenclosed elevator, the same shall be constructed
so as to form a substantial floor surface when closed and so arranged
as to open and close by the action of the elevator in its passage
either ascending or descending.
(2)
Except as otherwise provided by law or ordinance,
the Superintendent of Buildings shall have power and authority to
require the openings of hoistways, elevators and wellholes in buildings
to be enclosed or secured by trapdoors, guards or gates and railings.
(3)
All guards or gates required by this section shall
be kept closed at all times, except when in actual use, and the trapdoors
shall be closed at the close of the business of each day by the occupant
or occupants of the building having the use or control of the same.
A.
Protection of exterior opening required. Every opening
in the exterior walls of public and business structures more than
40 feet high, which is distant in a direct line less than 30 feet
from any frame structure or from any opening in any other structure
and in a different plane or is less than 50 feet in a vertical direction
above a nonfireproof roof of an adjoining structure within a distance
of 30 feet of the wall in which the opening is located, shall be equipped
with a protective opening having a fire-resistive rating of 3/4 hour,
except that one-fourth-inch-thick plate glass may be used on the street
fronts of such structures, regardless of the separation from other
structures, and all windows shall be of the automatic type or fixed
sash type, and all doors shall be self-closing.
B.
Exterior window frames and sash. When the height of
a structure exceeds 150 feet, all exterior window frames and sash
shall be of incombustible materials throughout the full height of
the structure.
C.
Protection of openings in exterior stairs, fire towers
and fire escapes. Door and window openings, where permitted on exterior
stairs. fire towers and fire escapes or under or adjacent to exterior
stairs or fire escapes, shall be protected by self-closing fire doors
or fixed or automatic fire windows or automatic fire shutters. Doors,
windows and shutters in openings serving as means of egress to exterior
stairs, fire towers and fire escapes shall be so arranged as not to
obstruct any exit.
D.
Protection of open shafts. In open shafts having a
cross-sectional area at any point of 36 square feet or less, openings
shall be equipped with protective assemblies having a fire-resistive
rating of at least 3/4 hour, except that this provision shall not
apply to such openings in shafts of private dwelling structures when
the openings are at least three feet distant from any other structure.
E.
Fire shutters to open readily. When fire shutters
are used in exterior openings, at least one row in every three vertical
rows of shutters on front window openings shall be arranged to open
readily from the outside. Distinguishing marks shall be provided on
these shutters as required by the Superintendent of Buildings.
F.
Vertical separation of windows.
(1)
In business structures over 40 feet high, exterior
openings above the second story, which are located vertically above
one another, shall have a space of at least three feet between the
top of one opening and the bottom of the one next above. Such space
shall be enclosed with materials having a fire-resistive rating as
required for exterior walls or of any other form of construction having
a fire-resistive rating of three hours.
(2)
A maximum of one-third (1A) of the height of such
enclosing materials may be replaced by wire glass in fixed metal sash
and trim or other assemblies having equivalent fire-resistive properties.
G.
Closing of protective assemblies. Protective assemblies
on exterior openings, unless provided with approved automatic closing
devices operative from either side, shall be closed when not required
to be open and, at the close of business each day, shall be closed
by the occupant or occupants of the structure having the use or control
of them.
H.
Protection of openings in lot line walls. All openings
in walls erected on the lot lines shall be protected by fixed self-closing
or automatic-closing assemblies having a fire-resistive rating of
at least 3/4 hour.
A.
Protection of openings in fire walls. The maximum
area of an opening in a fire wall shall be 80 square feet, the total
width of all openings on any level less than 25% of the length of
the wall, except that openings for the passage of motor trucks may
be a maximum of 140 square feet and the minimum distance between such
openings shall be three feet unless special permission is secured
from the Superintendent of Buildings. Each opening, except where used
as a required means of exit, shall be equipped with an automatic protective
assembly or an automatic and self-closing protective assembly having
a fire-resistive rating of three hours. Where openings in the fire
wall are used as exits, at least one such exit shall be equipped with
a self-closing protective assembly of a three-hour fire-resistive
rating on each side of the exit, and other exit openings shall have
an automatic and self-closing assembly of equal rating.
B.
Protection of openings in fire partitions. The only
openings permitted in fire partitions shall be those required for
doors and there shall be but one opening, unless the provision of
additional openings would not exceed 25% of the length of the wall
in total width. The maximum area for a door opening shall be 80 square
feet, except that openings for the passage of motor trucks may be
a maximum of 140 square feet, and each opening shall be equipped with
a self-closing protective assembly having a fire-resistive rating
of 1 1/2 hours.
C.
Protection of openings in fireproof partitions. The
only openings permitted in fireproof partitions enclosing public hallways
leading to required exits shall be those required for doors. Each
opening shall be equipped with a self-closing protective assembly
having a fire-resistive rating of at least 3/4 hour.
D.
Protection of openings in interior shafts.
(1)
Protection of openings in vent shafts. Openings into
vent shafts, except nonfireproof vent shafts, shall be equipped with
protective assemblies having a fire-resistive rating of one hour.
(2)
Protection of openings in elevator shafts. Doors opening
into elevator shafts shall be equipped with protective assemblies
having a fire-resistive rating of 1 1/2 hours, except that where
the elevator shaft opens into a vestibule constructed of materials
or assemblies having a fire-resistive rating of at least three hours
and in which openings are protected by assemblies having a fire-resistive
rating of at least 3/4 hour, the openings into the elevator shaft
shall be protected by assemblies having a fire-resistive rating of
at least 3/4 hour. Other openings into such shafts, except window
openings to the outer air and openings to elevator machinery rooms,
are forbidden.
(3)
Protection of openings in dumbwaiter shafts. Openings
in dumbwaiter shafts shall be equipped with self-closing protective
assemblies having a fire-resistive rating of 3/4 hour.
(4)
Protection of openings in other shafts. Openings in
shafts otherwise unprovided for in this subsection shall be equipped
with self-closing protective assemblies having a fire-resistive rating
of 1 1/2 hours, except that where such a shaft opens into a vestibule
constructed of materials or assemblies having a fire-resistive rating
of at least three hours and in which openings are protected by assemblies
having a fire-resistive rating of at least 3/4 hour, the openings
into the shaft shall be protected by assemblies having a fire-resistive
rating of at least 1/4 hour.
E.
Protection of openings in basement and cellar partitions. In nonfireproof structures, except structures occupied exclusively for residence purposes by one or two families, openings in cellar partitions required by § 86-17, Restrictions as to height and area, or in any story more than 1/2 below the curb shall have self-closing protective assemblies having a fire-resistive rating of 1 1/2 hours or fixed or self-closing windows having a fire-resistive rating of 3/4 hour.
F.
Separation of attached or built-in garages. Where private garages are attached to or form a part of a story within a residential structure of Class 1 Nonfireproof Structures or Class 4 Wood Frame Structures, walls, ceilings and floors enclosing such garages shall be separated from the remainder of the structure by assemblies having a fire-resistive rating of one hour, and all openings between the garage and the remainder of the structure shall be provided with self-closing or automatic protective assemblies having a fire-resistive rating of 3/4 hour, except as may be otherwise provided in Article XVII, Multiple Dwellings. Where living quarters are located above such a garage, the egress facilities from the living quarters shall not pass through the garage section.
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.
A.
Doors for openings in fire walls shall be constructed
without any glass.
B.
Doors for openings in fire partitions may be constructed
with glass, provided that they meet the fire-resistive requirements
for such doors, except that in structures used exclusively as schools,
hospitals, museums and libraries, vision panels having a maximum total
area of four square feet per door and divided into panes with a maximum
area of one square foot per pane shall be permitted.
C.
Doors for openings in fireproof partitions may be
constructed with a total maximum exposed area of wired glass of 720
square inches.
D.
All wired glass shall be at least 1/4 inch thick and
shall enclose a layer of wire fabric reinforcement having a maximum
mesh of 7/8 inch, and the size of the wire shall be at least No. 25
steel wire gauge or of equivalent fire-resistive qualities and shall
be set at least 5/8 inch into the frame.
A.
In Class 3 Nonfireproof Structures and in commercial
buildings of Class 4 construction, the ceilings of all stories below
grade and over the lowest story, if such story is partially below
the curb or surrounding ground level, shall be covered with metal
lath and plaster, plasterboard and plaster, plasterboard and sheet
metal, one-half-inch plasterboard and one-eighth-inch-thick hard asbestos
cement composition sheets with joints covered with two-inch-wide battens
of the same material or approved metal strips or other material having
a fire-resistive rating of one hour. In Class 3 Nonfireproof Structures
heretofore erected in which the classification by occupancy is hereafter
changed to business, cellar ceilings, if not already of fireproof
construction, shall be of materials or assemblies having a fire-resistive
rating of at least one hour. Such a ceiling, however, shall not be
required if the floor construction immediately above this lower story
is of incombustible material having a fire-resistive rating of at
least three hours.
B.
The ceilings of motion-picture theaters or other structures
for public assemblage not required to be fireproof as well as all
rooms, entrances or exits used in connection therewith shall have
ceilings of five-eighths-inch unsanded gypsum plaster or seven-eighths-inch
cement or sanded gypsum plaster on metal lath, measured from the face
of the lath, or any form of construction having, a fire-resistive
rating of one hour as required by the rules of the Superintendent
of Buildings.
A.
Materials required for roof structures and roofing.
All construction, other than water tanks, hereinafter placed above
the roof of any part of any structure within the fire limits or of
any structure more than 40 feet in height outside of the fire limits
shall be of incombustible materials, except when otherwise specifically
provided for in this code.
B.
Bulkheads.
(1)
The walls of any bulkhead hereafter erected on the roof of a fireproof structure shall be constructed of incombustible material having a fire-resistive rating of one hour and shall be covered on the outside with material meeting the requirements of Subsection K, Roofing, unless constructed in accordance with § 86-60, Masonry construction.
C.
Penthouses. The exterior walls of penthouses shall consist of materials having a fire-resistive rating of three hours and shall be covered on the outside with material meeting the requirements of Subsection K(1), Materials for roofing, unless constructed in accordance with § 86-60, Masonry construction. Floors of such structures shall be constructed as required for the other floors of the structure.
D.
Doors and windows. Doors, door frames and windows
in bulkheads or penthouses, except where otherwise specifically provided
for, shall be constructed as other doors, door frames and windows
similarly located in the structure.
E.
Greenhouses and conservatories. Greenhouses or conservatories
may be erected on the roof of any structure, provided that only incombustible
materials are used in their construction, and the floors of such structures
are constructed as required for the other floors of the structure.
F.
Dormers. Dormers hereafter erected shall be constructed in the same manner as the roof on which they are placed. The sides and top shall be covered with material meeting the requirements of Subsection K(2), Fire tests of roof coverings.
G.
Skylights.
(1)
The frame and sash of all skylights shall be constructed
of metal, except that in structures in which corrosive fumes are present,
wood frame and sash may be permitted in the discretion of the Superintendent
of Buildings. The frames and other parts of skylights shall be securely
anchored to the supporting structure.
(2)
Skylights placed over shafts, including stairways,
shall be glazed with plain glass 3/16 inch or less in thickness. The
maximum area of any pane of glass used in such skylights shall be
720 square inches. Skylights over places other than shafts shall be
glazed with wire glass.
(3)
Skylights in which plain glass is used shall be protected
by wire screens placed between four and 10 inches above the glazed
portion of the skylight at all points. Such screen shall be of No.
12 steel wire gauge or heavier, the wire shall have a mesh between
3/4 inch and one inch and shall extend beyond the glazing on all sides
for a distance of at least the height of the screen above the glazing.
When any such skylight is located over any passageway, stairway, elevator
or any occupied room, a similar screen shall also be placed below
the skylight.
H.
Scuttles. Unless provided with some other means of
access to the roof, every structure over 15 feet high, except roofs
with a pitch greater than 20° from the horizontal, shall have
a scuttle in the roof with a substantial ladder leading to it. Scuttles
shall be covered on the top and edges with sheet metal or other approved
incombustible material. Scuttle openings shall be at least two feet
by three feet in size.
I.
Tanks.
(1)
Tanks of more than 500 gallons of capacity hereafter
placed in or on any structure shall be supported on masonry, reinforced
concrete or steel construction.
(2)
Every tank shall have, in the bottom or on the side
near the bottom, a pipe or outlet at least two inches in diameter
and fitted with a suitable valve for discharging the contents in an
emergency.
(3)
The location of a tank over or near a line of stairs
or an elevator shaft is forbidden unless there is a solid roof or
floor underneath the tank.
(4)
Unenclosed roof tanks shall have covers sloping at
an angle of at least 30°.
(5)
When hoops are used in the construction of tanks,
they shall be of metal and round in section.
J.
Cooling towers. Cooling towers hereafter erected above
any roof shall be of incombustible material, except the drip bars
which may be of wood.
K.
Roofing.
(1)
Materials for roofing. Every roof hereafter placed
on a structure shall be covered with an approved roofing of brick,
concrete, tile, slate, metal asbestos or built-up roofing finished
with asphalt, slag or gravel or with other approved fire-retardant
material.
(2)
Fire tests of roof coverings. All roof coverings shall
be subject to a brand test. The fire test specifications of the American
Society for Testing Materials, D, C19-26T, shall be used and will
be accepted by the Superintendent of Buildings when made by a laboratory
of recognized reputation.
L.
Slanting roofs, mansards and dormers.
(1)
Every mansard or other slanting roof having a pitch of more than 30° placed on any non-fireproof structure over 40 feet high shall be constructed in accordance with the provisions of § 86-71G, Special roof construction.
(2)
Every mansard or other slanting roof having a pitch of less than 30° placed on any non-fireproof structure may be constructed of the same materials as the roof construction of the structure, provided that the face and back of the mansard or slanting roof is covered with roofing material meeting the requirements of Subsection K(2), Fire tests of roof coverings.
M.
Cornices, gutters and half-timber decoration. Cornices
and gutters, inclusive of those on show windows, hereafter placed
or replaced on the exterior of any structure, except structures of
frame construction, shall be of incombustible materials, except that
wood half-timbering and other wood decorative treatment may be used
on the face of masonry construction in structures of Class 3 and Class
6 construction and less than 45 feet in height. Such cornices and
gutters shall be secured to the wall with metal brackets and anchors
with a maximum spacing of four feet and extending at least four inches
into the wall at the top and bottom.
N.
Signs. All materials used for the framing of signs
or for their support upon the roofs or any part of any such structures
within the fire limits or of any such structures more than 40 feet
in height outside the fire limits shall be constructed of incombustible
materials.
A.
Firestopping required.
(1)
Structures, whether fireproof or nonfireproof, shall
have all concealed draft openings firestopped with incombustible material
to form an effectual fire barrier between stories and between the
upper story and the roof space.
B.
Firestopping of openings for pipes, belts and shafting.
(1)
Openings around exposed pipes, belts or power shafting
shall be filled with incombustible material or shall be closed off
by close fitted metal caps at the ceiling and floor line or on each
side of the wall. For nonfireproof construction, metal sleeves shall
be provided in addition to the caps.
(2)
Openings for belts shall be provided with approved
slotted doors or otherwise closed off. Belts shall not pass through
fire walls or fire partitions.
C.
Firestopping of furred walls, partitions and concealed
roof spaces. Walls, including masonry walls furred with combustible
material, and stud bearing partitions shall be fire-stopped with incombustible
material at floors, ceilings and roofs. The firestopping shall extend
from the ceiling to the underside of the flooring or roofing. Concealed
roof spaces in Class 3 Nonfireproof structures shall be cut off into
areas of 2,500 square feet or less by firestops.
D.
Firestopping of stairs. Stairs, except in one- and two-family residence structures, shall be fire-stopped between wooden stair carriages by headers at top and bottom. The location of closets beneath stairs is forbidden, except in Class 1 Fireproof Structures, unless they are entirely lined with incombustible material. The underside of stairs of combustible material shall be covered with metal lath and plaster to a total thickness of 3/4 inch, measured from the back of the lath, or with plasterboard and a minimum of one-half-inch unsanded gypsum plaster or one-half-inch-thick plasterboard covered with one-eighth-inch-thick hard asbestos cement composition boards with joints covered with a two-inch batten strip of the same material or approved metal strips, except where such stairs are enclosed by a partition of lawful construction as specified in Article VII, Means of Egress.
E.
Materials for firestopping. Firestopping shall be
done with the following materials: brick, concrete, gypsum, asbestos,
metal lath and cement or gypsum plaster, mineral wool, rock wool or
other approved materials.
