Does Stair Structure Have to be Fire-Rated?

6/8/2023

If a stair structure is supporting the fire barriers that enclose the exit enclosure, does the stair structure have to be fire rated as well?

Looking specifically at IBC 2018 Section 707.5.1 and NFPA 101 (2018) Section 7.1.3.2.

If there is a fire inside a stair, the means of egress is no longer usable and at that point are you protecting the interior of the building from the fire inside the exit enclosure?

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5 Comments

Glenn Berger

6/8/2023 08:14:51 am

You always want the exit stair to be a safe, protected enclosure. If the event happens within one of the enclosures, then the other exit is used.

SCHULMAN

6/8/2023 08:22:43 am

any structure supporting rated construction also has to be constructed of materials rated to the same (fire resisting) duration as the enclosure ... any steel stair should do the job if I understand the question correctly. If someone is trying to build a rated egress stair out of wood I would question the method ...

Todd E Wyatt

6/8/2023 08:52:30 am

SUMMARYIf the "stairway" is an Interior Exit Stairway (IES) or an Exit Access Stairway (EAS), it is required to be protected by fire-resistance rated (FRR) Fire Barriers (FB) and the supporting construction (floor construction & primary structure) is also required to have the same FRR as the FBs.
EXPLANATIONInterior Exit Stairway (IES) are required to be "not less than 2 hours where connecting four stories or more and not less than 1 hour where connecting less than four stories." If the IES penetrates a Floor Construction (based on the building's Type of Construction) of 2-hours or greater, the IES shall be protected by 2-Hour Fire Barriers (2FB) regardless of the stories connected.
Exit Access Stairways (EAS) in other than Groups I-2 and I-3 "shall be enclosed with a shaft enclosure constructed in accordance with Section 713" unless it meets one of the exceptions in 2021 IBC 1019.3. Like IES, shafts "shall have a fire-resistance rating of not less than 2 hours where connecting four stories or more, and not less than 1 hour where connecting less than four stories." EAS that "serve floor levels within a single story are not required to be enclosed" however.
In buildings of Types IIB, IIIB and VB construction, supporting construction is NOT required to be FRR IF it supports 1FBs per Section 718.2 Exception 2. In buildings of Types IIB, IIIB and VB construction, supporting construction IS required to be FRR IF it supports 2FBs.

Todd E Wyatt

6/8/2023 08:54:12 am

REFERENCES
2021 IBC
Chapter 7 Fire and Smoke Protection Features
Section 707 Fire Barriers
707.3 Fire-Resistance Rating
The fire-resistance rating of fire barriers shall comply with this section.707.3.2 Interior Exit Stairway and Ramp Construction
The fire-resistance rating of the fire barrier separating building areas from an interior exit stairway or ramp shall comply with Section 1023.1.
707.3.3 Enclosures for Exit Access Stairways
The fire-resistance rating of the fire barrier separating building areas from an exit access stairway or ramp shall comply with Section 713.4.
707.5 Continuity
Fire barriers shall extend from the top of the foundation or floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto. Such fire barriers shall be continuous through concealed space, such as the space above a suspended ceiling. Joints and voids at intersections shall comply with Sections 707.8 and 707.9
Exceptions:
2. Interior exit stairway and ramp enclosures required by Section 1023 and exit access stairway and ramp enclosures required by Section 1019 shall be permitted to terminate at a top enclosure complying with Section 713.12.
707.5.1 Supporting Construction
The supporting construction for a fire barrier shall be protected to afford the required fire-resistance rating of the fire barrier supported. Hollow vertical spaces within a fire barrier shall be fireblocked in accordance with Section 718.2 at every floor level.
Exceptions:
2. Supporting construction for 1-hour fire barriers required by Table 509.1 in buildings of Types IIB, IIIB and VB construction is not required to be fire-resistance rated unless required by other sections of this code.

Section 713 Shaft Enclosures
713.2 Construction
Shaft enclosures shall be constructed as fire barriers in accordance with Section 707 or horizontal assemblies in accordance with Section 711, or both.
713.3 Materials
Shaft enclosures shall be of materials permitted by the building type of construction.
713.4 Fire-Resistance Rating
Shaft enclosures shall have a fire-resistance rating of not less than 2 hours where connecting four stories or more, and not less than 1 hour where connecting less than four stories. The number of stories connected by the shaft enclosure shall include any basements but not any mezzanines. Shaft enclosures shall have a fire-resistance rating not less than the floor assembly penetrated, but need not exceed 2 hours. Shaft enclosures shall meet the requirements of Section 703.2.1.1.

Chapter 10 Means of Egress
Section 1011 Stairways

Section 1019 Exit Access Stairways and Ramps
1019.1 General
Exit access stairways and ramps serving as an exit access component in a means of egress system shall comply with the requirements of this section. The number of stories connected by exit access stairways and ramps shall include basements, but not mezzanines.
1019.2 All Occupancies
Exit access stairways and ramps that serve floor levels within a single story are not required to be enclosed.
1019.3 Occupancies Other Than Groups I-2 and I-3
In other than Group I-2 and I-3 occupancies, floor openings containing exit access stairways or ramps shall be enclosed with a shaft enclosure constructed in accordance with Section 713.
Exceptions:
Exit access stairways and ramps that serve or atmospherically communicate between only two adjacent stories. Such interconnected stories shall not be open to other stories.In Group R-1, R-2 or R-3 occupancies, exit access stairways and ramps connecting four stories or less serving and contained within an individual dwelling unit or sleeping unit or live/work unit.Exit access stairways serving and contained within a Group R-3 congregate residence or a Group R-4 facility are not required to be enclosed.Exit access stairways and ramps in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1, where the area of the vertical opening between stories does not exceed twice the horizontal projected area of the stairway or ramp and the opening is protected by a draft curtain and closely spaced sprinklers in accordance with NFPA 13. In other than Group B and M occupancies, this provision is limited to openings that do not connect more than four stories.Exit access stairways and ramps within an atrium complying with the provisions of Section 404.Exit access stairways and ramps in open parking garages that serve only the parking garage.Exit access stairways and ramps serving smoke-protected or open-air assembly seating complying with the exit access travel distance requirements of Section 1030.7.Exit access stairways and ramps between the balcony, gallery or press box and the main assembly floor in occupancies such as theaters, places of religious worship, auditoriums and sports facilities.Exterior exit access stairways or ramps between occupied roofs.
Section 1023 Interior Exit Stairways and Ramps
1023.2 Constructio

JP link

6/8/2023 12:26:30 pm

Todd I believe nailed it. Overall the intention of the code is for the entire means of egress to meet the minimum required fire resistance rating (i.e. 1 or two hours usually). The code typically assumes that a fire will not be located in the exit enclosure especially with other requirements limiting combustibles and non essential penetrations into the stair enclosure. A fire in the exit enclosure leans toward arson. The requirements are not typically meant to deal with intentional fires.

Does Stair Structure Have to be Fire-Rated?

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