Exit Stair Required to Have Solid Treads/Risers?

8/22/2024

In NFPA 101, is a solid riser and a solid tread required for an Exit Stair?

See the image below that is metal tread but wouldn't have solid risers. Thanks in advance.

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8 Comments

Todd E Wyatt

8/22/2024 08:20:22 am

The Means of Egress component shown appears to be an Alternating Tread Device (ATD) and not a Stair.

ATDs are not required to have solid treads and landings as Stairs do (7.2.2.3.3.1, see below).

Todd E Wyatt

8/22/2024 08:21:05 am

NFPA 101-2012
Chapter 7 Means of Egress
7.2 Means of Egress Components.
7.2.11* Alternating Tread Devices

Enhanced Content
As used in the Code, an alternating tread device is an intermediate form of climbing implement that is a cross between a ladder and a stair. It consists of a steep succession of half-width treads that alternate from the left side to the right side at intervals of one riser height. A person using the device is forced to place the correct foot on each tread. This alternating tread design, now generally manufactured as a series of treads supported by a central spine, permits stairlike half-treads to be used with ladderlike slopes. The use of such devices, which might be awkward due to unfamiliarity or infrequent use, might be acceptable for some occupancies and locations where the alternative means of changing levels are ladders or ships’ ladders, devices that generally have pitches of 50 degrees to 75 degrees. Such pitches are approximately twice those permitted for stairs by the Code.

An advantage of alternating tread devices is that one can descend with one’s back to the device — unlike a ladder where one can only descend safely while facing the ladder because of the more limited surface area and depth of ladder rungs. A further benefit of the device is that objects can be carried more easily while ascending or descending, because the handrails provide support under the arms, which are left free.

The Code limits the use of alternating tread devices to those situations where a ladder is acceptable.

7.2.11.1
Alternating tread devices complying with 7.2.11.2 shall be permitted in the means of egress only where providing one of the following:
1) Access to unoccupied roof spaces as permitted in 7.2.8.3.4
2) Second means of egress from storage elevators as permitted in Chapter 42
3) Means of egress from towers and elevated platforms around machinery or similar spaces subject to occupancy not to exceed three persons who are all capable of using the alternating tread device
4) Secondary means of egress from boiler rooms or similar spaces subject to occupancy not to exceed three persons who are all capable of using the alternating tread device
7.2.11.2
Alternating tread devices shall comply with all of the following:
1) Handrails shall be provided on both sides of alternating tread devices in accordance with 7.2.2.4.4, except as provided in 7.2.11.3.
2) The clear width between handrails shall be not less than 17 in. (430 mm) and not more than 24 in. (610 mm).
3) Headroom shall be not less than 6 ft 8 in. (2030 mm).
4) The angle of the device shall be between 50 degrees and 68 degrees to horizontal.
5) The height of the riser shall not exceed 91⁄2 in. (240 mm).
6) Treads shall have a projected tread depth of not less than 54⁄5 in. (145 mm), measured in accordance with 7.2.2, with each tread providing 91⁄2 in. (240 mm) of depth, including tread overlap.
7) A distance of not less than 6 in. (150 mm) shall be provided between the alternating tread device handrail and any other object.
8) The initial tread of the alternating tread device shall begin at the same elevation as the platform, landing, or floor surface.
9) The alternating treads shall not be laterally separated by a distance of more than 2 in. (51 mm).
10) The occupant load served shall not exceed three.
7.2.11.3
Handrails of alternating tread devices shall comply with the following:
1) The handrail height of alternating tread devices, measured above tread nosings, shall be uniform, not less than 30 in. (760 mm), and not more than 34 in. (865 mm).
2) Handrails for alternating tread devices shall be permitted to terminate at a location vertically above the top and bottom risers.
3) Handrails for alternating tread devices shall not be required to be continuous between flights or to extend beyond the top or bottom risers.
4) Alternating tread device guards, with a top rail that also serves as a handrail, shall have a height of not less than 30 in. (760 mm), and not more than 34 in. (865 mm), measured vertically from the leading edge of the device tread nosing.
5) Open guards of alternating tread devices shall have rails such that a sphere 21 in. (535 mm) in diameter is not able to pass through any opening.

7.2.2 Stairs.
7.2.2.3 Stair Details.
7.2.2.3.3 Tread and Landing Surfaces.
7.2.2.3.3.1
Stair treads and landings shall be SOLID, without perforations, unless otherwise permitted in
7.2.2.3.3.4
The requirement of 7.2.2.3.3.1 shall not apply to noncombustible GRATED stair treads and landings in the following occupancies:
1) Assembly occupancies as otherwise provided in Chapters 12 and 13
2) Detention and correctional occupancies as otherwise provided in Chapters 22 and 23
3) Industrial occupancies as otherwise provided in Chapter 40
4) Storage occupancies as otherwise provided in Chapter 42

Enhanced Content
Solid treads and solid landing floors provide a visual barrier that shields the user&rsquo

Todd E Wyatt

8/22/2024 08:21:38 am

Enhanced Content
Solid treads and solid landing floors provide a visual barrier that shields the user’s view of the vertical drop beneath the stair. Persons with a fear of high places are more comfortable using such stairs. Grated and expanded metal treads and landings might catch a user’s heel and present a tripping hazard. Noncombustible, grated stair treads are permitted in areas not accessed by the general public, such as catwalks and gridirons in theaters, resident housing areas in prisons, factories and other industrial occupancies, and storage occupancies.

Brett

8/22/2024 09:05:32 am

The picture provided is not an alternate tread device. Here is what an ATD looks like.
https://www.fsindustries.com/more_info/steel_alternating_tread_stair/steel_alternating_tread_stair.shtml?gad_source=1&gclid=Cj0KCQjww5u2BhDeARIsALBuLnPu5-budCZFjes1U0jmJtv4v5UdZopPeZl4U10QzHzW5XXWrakm2B8aAhvOEALw_wcB

They're mostly used in industrial settings or on marine vessels.

Todd E Wyatt

8/22/2024 04:26:00 pm

CORRECTION
This "stair" appears to be a "SHIP’S LADDER" which is not referenced by NFPA 101-2012 but is referenced in the ENHANCED CONTENT :

7.2.11* Alternating Tread Devices.

Enhanced Content
As used in the Code, an alternating tread device is an intermediate form of climbing implement that is a cross between a ladder and a stair. It consists of a steep succession of half-width treads that alternate from the left side to the right side at intervals of one riser height. A person using the device is forced to place the correct foot on each tread. This alternating tread design, now generally manufactured as a series of treads supported by a central spine, permits stairlike half-treads to be used with ladderlike slopes. The use of such devices, which might be awkward due to unfamiliarity or infrequent use, might be acceptable for some occupancies and locations where the alternative means of changing levels are ladders or SHIPS’ LADDER, devices that generally have pitches of 50 degrees to 75 degrees. Such pitches are approximately twice those permitted for stairs by the Code.

An advantage of alternating tread devices is that one can descend with one’s back to the device — unlike a ladder where one can only descend safely while facing the ladder because of the more limited surface area and depth of ladder rungs. A further benefit of the device is that objects can be carried more easily while ascending or descending, because the handrails provide support under the arms, which are left free.

The Code limits the use of alternating tread devices to those situations where a ladder is acceptable. The exhibit below shows an alternating tread device.

The IBC-2021 does reference SHIP’S LADDERS as a type of Stairway :

Section 1011 Stairways
1011.1 General
Stairways serving occupied portions of a building shall comply with the requirements of Sections 1011.2 through 1011.13. Alternating tread devices shall comply with Section 1011.14. SHIP’S LADDERS shall comply with Section 1011.15. Ladders shall comply with Section 1011.16.

1011.15 SHIP’S LADDERS
SHIP’S LADDERS are permitted to be used in Group I-3 as a component of a means of egress to and from control rooms or elevated facility observation stations not more than 250 square feet (23 m2) with not more than three occupants and for access to unoccupied roofs. The minimum clear width at and below the handrails shall be 20 inches (508 mm). SHIP’S LADDERS shall be designed for the live loads indicated in Section 1607.17.
1011.15.1 Handrails of SHIP’S LADDERS
Handrails shall be provided on both sides of ship's ladders.
1011.15.2 Treads of SHIP’S LADDERS
Ship's ladders shall have a minimum tread depth of 5 inches (127 mm). The tread shall be projected such that the total of the tread depth plus the nosing projection is not less than 81/2 inches (216 mm). The maximum riser height shall be 9 1/2 inches (241 mm).

Todd E Wyatt

8/22/2024 08:33:55 am

Solid risers in stairs (stairways) are not required per NFPA 101-2012 but are per IBC :

IBC-2021
Chapter 10 Means of Egress
Section 1011 Stairways
1011.5 Stair Treads and Risers
1011.5.5 Nosing and Riser Profile
1011.5.5.3 Solid Risers
Risers shall be solid.
Exceptions:
1) Solid risers are not required for stairways that are not required to comply with Section 1009.3, 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 I-3 or in Group F, H and S occupancies other than areas accessible to the public. The size of the opening in the riser is not restricted.
3) Solid risers are not required for spiral stairways constructed in accordance with Section 1011.10.

Section 1009 Accessible Means of Egress
1009.3 Stairways

If the STAIRWAY is not required to be part of the Accessible Means of Egress (AME), solid risers are not required.

If the STAIRWAY is not to be used by the Public in Group I-3 or F, H, and S occupancies, solid risers are not required.

Jack G

8/22/2024 08:34:59 am

Todd says it all. Agree!
The plans code sheet would indicate the codes for the egress stairs.

Brett

8/22/2024 09:15:43 am

One thing to consider is if the stairs are located on the exterior of the building you must consider height and the requirement for a visual barrier.

7.2.2.6.2* Visual Protection.
Outside stairs shall be arranged to avoid any impediments to their use by persons having a fear of high places. Outside stairs more than 36 ft (11 m) above the finished ground level, other than previously approved existing stairs, shall be provided with an opaque visual obstruction not less than 48. in. (1220 mm) in height.

Exit Stair Required to Have Solid Treads/Risers?

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