SECTION
1009 STAIRWAYS
1009.1
Stairway width. The width of stairways shall be determined
as specified in Section 1005.1,
but such width shall not be less than 44 inches (1118 mm).
See Section 1007.3 for accessible
means of egress stairways.
Exceptions:
1. Stairways serving an occupant load of less than 50 shall
have a width of not less than 36 inches (914 mm).
2. Spiral stairways as provided
for in Section 1009.8.
3. Aisle stairs complying
with Section 1025.
4. Where an incline platform lift or stairway chairlift
is installed on stairways serving occupancies in Group R
- 3, or within dwelling units in occupancies in Group R
- 2, a clear passage width not less than 20 inches (508
mm) shall be provided. If the seat and platform can be folded
when not in use, the distance shall be measured from the
folded position.
1009.2
Headroom. Stairways shall have a minimum headroom clearance
of 80 inches (2032 mm) measured vertically from a line connecting
the edge of the nosings. Such headroom shall be continuous
above the stairway to the point where the line intersects
the landing below, one tread depth beyond the bottom riser.
The minimum clearance shall be maintained the full width of
the stairway and landing.
Exception: Spiral stairways complying with Section 1009.8
are permitted a 78-inch (1981 mm) headroom clearance.
1009.3
Stair treads and risers. Stair riser heights shall be
7 inches (178 mm) maximum and 4 inches (102 mm) minimum. Stair
tread depths shall be 11 inches (279 mm) minimum. The riser
height shall be measured vertically between the leading edges
of adjacent treads. The tread depth shall be measured horizontally
between the vertical planes of the foremost projection of
adjacent treads and at aright angle to the tread's leading
edge. Winder treads shall have a minimum tread depth of 11
inches (279 mm) measured at a right angle to the tread's leading
edge at a point 12 inches (305 mm) from the side where the
treads are narrower and a minimum tread depth of 10 inches
(254 mm).
Exceptions:
1. Alternating tread devices in accordance with Section
1009.9.
2. Spiral stairways in accordance
with Section 1009.8.
3. Aisle stairs in assembly
seating areas where the stair pitch or slope is set, for
sightline reasons, by the slope of the adjacent seating
area in accordance with Section
1025.11.2.
4. In Group R-3 occupancies;
within dwelling units in Group R-2 occupancies; and in
Group U occupancies that are accessory to a Group R -
3 occupancy or accessory to individual dwelling units
in Group R-2 occupancies; the maximum riser height shall
be 7.75 inches (197 mm); the minimum tread depth shall
be 10 inches (254 mm); the minimum winder tread depth
at the walk line shall be 10 inches (254 mm); and the
minimum winder tread depth shall be 6 inches (152 mm).
A nosing not less than 0.75 inch (19.1 mm) but not more
than 1.25 inches (32 mm) shall be provided on stairways
with solid risers where the tread depth is less than 11
inches (279 mm).
5. See the
Section 3403.4 for the replacement of existing stairways.
1009.3.1 Winder treads. Winder treads are not permitted
in means of egress stairways except within a dwelling unit.
Exceptions:
1. Curved stairways in accordance with Section 1009.7.
2.
Spiral stairways in accordance with Section 1009.8.
1009.3.2
Dimensional uniformity. Stair treads and risers shall
be of uniform size and shape. The tolerance between the
largest and smallest riser height or between the largest
and smallest tread depth shall not exceed 0.375 inch (9.5
mm) in any flight of stairs. The greatest winder tread depth
at the 12-inch (305 mm) walk line within any flight of stairs
shall not exceed the smallest by more than 0.375 inch (9.5
mm) measured at a right angle to the tread's leading edge.
Exceptions:
1. Nonuniform riser dimensions of aisle stairs complying
with Section 1025.11.2.
2. Consistently shaped winders, complying with Section
1009.3, differing from rectangular treads in the same
stairway flight.
Where
the bottom or top riser adjoins a sloping public way, walkway
or driveway having an established grade and serving as a landing,
the bottom or top riser is permitted to be reduced along the
slope to less than 4 inches (102 mm) in height, with the variation
in height of the bottom or top riser not to exceed one unit
vertical in 12 units horizontal (8-percent slope) of stairway
width. The nosings or leading edges of treads at such nonuniform
height risers shall have a distinctive marking stripe, different
from any other nosing marking provided on the stair flight.
The distinctive marking stripe shall be visible in descent
of the stair and shall have a slipresistant surface. Marking
stripes shall have a width of at least 1 inch (25 mm) but
not more than 2 inches (51 mm).
1009.3.3 Profile. The
radius of curvature at the leading edge of the tread shall
be not greater than 0.5 inch (12.7 mm). Beveling of nosings
shall not exceed 0.5 inch (12.7 mm). Risers shall be solid
and vertical or sloped from the underside of the leading
edge of the tread above at an angle not more than 30 degrees
(0.52 rad) from the vertical. The leading edge (no sings
) of treads shall project not more than 1.25 inches (32
mm) beyond the tread below and all projections of the leading
edges shall be of uniform size, including the leading edge
of the floor at the top of a flight.
Exceptions:
1. Solid risers are not required for stairways that are
not required to comply with Section
1007.3, provided that the opening between treads does
not permit the passage of a sphere with a diameter of 4
inches (102 mm).
2. Solid risers are not required
for occupancies in Group 1-3.
1009.4
Stairway landings. There shall be a floor or landing at
the top and bottom of each stairway. The width of landings
shall not be less than the width of stairways they serve.
Every landing shall have a minimum dimension measured in the
direction of travel equal to the width of the stairway. Such
dimension need not exceed 48 inches (1219 mm) where the stairway
has a straight run.
Exceptions:
1. Aisle stairs complying with
Section 1025.
2. Doors opening onto a landing shall not reduce the landing
to less than one-half the required width. When fully open,
the door shall not project more than 7 inches (178 mm) into
a landing.
1009.5
Stairway construction. All stairways shall be built of
materials consistent with the types permitted for the type
of construction of the building, except that wood handrails
shall be permitted for all types of construction.
1009.5.1 Stairway walking surface. The walking surface
of treads and landings of a stairway shall not be sloped
steeper than one unit vertical in 48 units horizontal (2-percent
slope) in any direction. Stairway treads and landings shall
have a solid surface. Finish floor surfaces shall be securely
attached.
Exception: In Group F, Hand S occupancies, other than
areas of parking structures accessible to the public, openings
in treads and landings shall not be prohibited provided a
sphere with a diameter of 1.125 inches (29 mm) cannot pass
through the opening.
1009.5.2 Outdoor conditions. Outdoor stairways and outdoor
approaches to stairways shall be designed so that water
will not accumulate on walking surfaces.
1009.5.3 Enclosures under stairways. The walls and soffits
within enclosed usable spaces under enclosed and unenclosed
stairways shall be protected by 1-hour fire-resistance-rated
construction or the fire-resistance rating of the stairway
enclosure, whichever is greater. Access to the enclosed
space shall not be directly from within the stair enclosure.
Exception:
Spaces under stairways serving and contained within a
single residential dwelling unit in Group R-2 or R-3 shall
be permitted to be protected on the enclosed side with 0.5-inch
(12.7 mm) gypsum board. There shall be no enclosed usable
space under exterior exit stairways unless the space is completely
enclosed in 1-hour fire-resistance-rated construction. The
open space under exterior stairways shall not be used for
any purpose.
1009.6
Vertical rise. A flight of stairs shall not have a vertical
rise greater than 12 feet (3658 mm) between floor levels or
landings.
Exception: Aisle stairs complying with Section
1025.
1009.7
Curved stairways. Curved stairways with winder treads
shall have treads and risers in accordance with Section 1009.3
and the smallest radius shall not be less than twice the required
width of the stairway.
Exception: The radius restriction shall not apply to curved
stairways for occupancies in Group R-3 and within individual
dwelling units in occupancies in Group R-2.
1009.8
Spiral stairways. Spiral stairways are permitted to be
used as a component in the means of egress only within dwelling
units or from a space not more than 250 square feet (23 m2)
in area and serving not more than five occupants, or from
galleries, catwalks and gridirons in accordance with Section
1015.6.
A
spiral stairway shall have a 7.5 inch (191 mm) minimum clear
tread depth at a point 12 inches (305 mm) from the narrow
edge. The risers shall be sufficient to provide a headroom
of 78 inches (1981 mm) minimum, but riser height shall not
be more than 9.5 inches (241 mm). The minimum stairway width
shall be 26 inches (660 mm).
1009.9
Alternating tread devices. Alternating tread devices are
limited to an element of a means of egress in buildings of
Groups F, Hand S from a mezzanine not more than 250 square
feet (23 m2) in area and which serves not more
than five occupants; in buildings of Group 1-3 from a guard
tower, observation station or control room not more than 250
square feet (23 m'2) in area and for access to
unoccupied roofs.
1009.9.1 Handrails of alternating
tread devices. Hand-rails shall be provided on both
sides of alternating tread devices and shall comply with
Section 1012.
1009.9.2 Treads of alternating tread devices. Alternating
tread devices shall have a minimum projected tread of 5
inches (127 mm), a minimum tread depth of 8.5 inches (216
mm), a minimum tread width of 7 inches (178 mm) and a maximum
riser height of 9.5 inches (241 mm). The initial tread of
the device shall begin at the same elevation as the platform,
landing or floor surface.
Exception: Alternating tread devices used as an element
of a means of egress in buildings from a mezzanine area not
more than 250 square feet (23 m2) in area which
serves not more than five occupants shall have a minimum projected
tread of 8.5 inches (216 mm) with a minimum tread depth of
10.5 inches (267 mm). The rise to the next alternating tread
surface should not be more than 8 inches (203 mm).
1009.10
Handrails. Stairways shall have handrails on each side
and shall comply with Section 1012.
Where glass is used to provide the handrail, the handrail
shall also comply with Section 2407.
Exceptions:
1. Aisle stairs complying with Section
1025 provided with a center handrail need not have additional
handrails.
2. Stairways within dwelling units, spiral stairways and
aisle stairs serving seating only on one side are permitted
to have a handrail on one side only.
3. Decks, patios and walkways that have a single change
in elevation where the landing depth on each side of the
change of elevation is greater than what is required for
a landing do not require handrails.
4.
In Group R-3 occupancies, a change in elevation consisting
of a single riser at an entrance or egress door does not
require handrails.
5. Changes in room elevations of only one riser within dwelling
units and sleeping units in Group R-2 and R-3 occupancies
do not require handrails.
1009.11
Stairway to roof. In buildings located four or more stories
in height above grade plane, one stairway shall extend to
the roof surface, unless the roof has a slope steeper than
four units vertical in 12 units horizontal (33-percent slope).
In buildings without an occupied roof, access to the roof
from the top story shall be permitted to be by an alternating
tread device.
1009.11.1 Roof access. Where a stairway is provided
to a roof, access to the roof shall be provided through
a penthouse complying with Section
1509.2.
Exception: In buildings without an occupied roof, access
to the roof shall be permitted to be a roof hatch or trap
door not less than 16 square feet (1.5 m2) in area
and having a minimum dimension of 2 feet (610 mm).
1009.11.2 Protection at roof hatch openings. Where the
roof hatch opening providing the required access is located
within 10 feet (3049 mm) of the roof edge, such roof access
or roof edge shall be protected by guards installed in accordance
with the provisions of Section 1013.
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