Overview of Requirements for Open Stairs

2/18/2021

In the A/E design community, the term "open stair" is frequently used to describe a stair that is not enclosed with walls, partitions or barriers. While "open stair" is not a term used in the International Building Code, it generally aligns with a stairway (which is a defined term in the IBC) not used for egress purposes or an exit access stairway (also a defined term). The terms "communicating stair" and "convenience stair" are also used in the same line of discussion, though depending on the situation, these could be referring to communicating spaces or convenience openings, both types of vertical openings defined in NFPA 101.

In this post, we'll review the IBC requirements for open stairs and describe several code paths that can be used to provide open stairs in your design. I will use the term "open stair" throughout the post, but remember, since this is not a defined term, any formal documentation on drawings, plans etc. should use the proper nomenclature identified in this overview. This post will be limited to stairs within a building and will not address exterior stairways.

Open Stairs - 2018 IBC Code Paths

Stairway Connecting Levels within a Story
The first and most simple type of open stair connects one or more levels within a single story. This stair could be provided to access a raised floor area or a mezzanine, or to access areas on a story that are at different elevations due to a sloping site.

Open stair connecting two levels within a lobby. (Image courtesy of Ceslou, CC BY-SA 4.0)

If the open stair is not used as part of the means of egress, the IBC would view it as simply a "stairway." If it is on the path of egress, it then becomes an exit access stairway. In either case, since this type of stair does not connect multiple stories, there is no code requirement to enclose the stairway or provide a rated separation (IBC 1019.2).

One other important point for this type of open stair is the requirement for accessible means of egress (IBC 1009). An exit access stair connecting levels on the same story is not permitted to be part of an accessible means of egress, unless the stair is providing the means of egress from a mezzanine (IBC 1009.3.1). If you are not sure how to address required vs. accessible means of egress requirements, check out this post for more details.

Stairway Connecting Two Stories
If your open stair does connect two stories, a few additional requirements are triggered. First, IBC 712.1.9 gives a number of requirements for vertical two-story openings. These include:

Does not penetrate a horizontal assembly separating a fire area or smoke compartment
Is not concealed within a wall, floor or ceiling assembly
Is not open to a Group I or R corridor
Is not open to any corridor on a nonsprinklered floor
Is separated from openings serving other floors by construction conforming to required shafts

An open stair connecting two stories.

If your open stair is part of the means of egress (exit access stairway), IBC 1019.3 gives similar requirements. Note that open stairs connecting two stories are not permitted in Group I-2 and I-3 occupancies.

Stairway Connecting Three or More Stories
If your open stair connects three or more stories, the most common approach is to use a draft curtain and closely spaced sprinklers per IBC 1019.3.4. Use of this provision requires the following:

The building must be fully sprinkler-protected in accordance with NFPA 13
The area of the vertical opening must not exceed twice the horizontal projected area of the stairway
The opening must be protected with a draft curtain and sprinklers per NFPA 13

An open stair connecting multiple stories with a draft curtain and closely-spaced sprinklers. (Image courtesy of HDI Railing Systems)

In Group B and M occupancies, there is no limit to the number of stories that can be connected with this approach. In all other occupancies, this is limited to four connected stories, except Groups I-2 and I-3, where it is not permitted at all.

Open Stairs in Group R Occupancies
In Group R-1, R-2 and R-3 occupancies, open stairs up to four stories are permitted if they are contained within a single dwelling unit, sleeping unit or live/work unit.

Open stairs are also permitted in Group R-3 congregate living facilities and Group R-4 occupancies.

An open stair located in a Group R-2 dwelling unit.

Open Stairs within an Atrium
If located within an atrium, open stairs are permitted with no limit to the number of stories connected. Keep in mind that atriums have a host of additional requirements in the code, such as smoke control and rated separation from other building spaces. Open stairs in an atrium are permitted to serve as exit access stairways, though the travel distance when using such stairs is limited to 200 feet (IBC 404.9.3).

An open stair connecting several levels within an atrium. (Image courtesy of Nheyob, CC BY-SA 3.0)

Other Situations
There are a few other situations where the code allows open stairs without any rated enclosure or separation:

In open parking garages where the stair serves only the parking garage
In smoke-protected or open-air assembly seating areas complying with IBC 1029.7
In theaters, auditoriums and sports facilities, open stairs connecting balconies, galleries or press boxes to the main assembly floor
Stairs within mall buildings complying with IBC 402

Conclusion

There are many cases where the IBC allows open stairs. When open stairs are used as part of the means of egress for a building, they are considered "exit access stairways." Otherwise, they would fall under the "stairway" definition in the code. If your project is required to comply with NFPA 101, be sure to check out Chapter 8, which has more stringent requirements for vertical openings than the IBC.

3 Comments

Jonathan Ochshorn link

6/27/2021 12:32:12 pm

Your advice on "open stairs within an atrium" is not quite correct.

There are two possible ways in which a stairway that is part of a means of egress can be unenclosed within an atrium, per the 2018 IBC.

Exit access stairways can be open in atriums, or anywhere else, as long as they do not pass through more than one adjacent story (see Section 1006.3.1 in the 2018 IBC). Section 1019.3, condition 5, does not contradict the requirement in Section 1006.3.1 that exit access stairways shall not pass through more than one adjacent story, but actually resolves a potential contradiction between the requirement in Section 1019.3 for “floor openings containing exit access stairways” to be “enclosed with a shaft enclosure” and the allowance in Section 404.6, exception 3, for any three floors of the atrium to be exempted from the atrium enclosure requirement. Without Section 1019.3, condition 5, an exit access stairway in an atrium would only be possible if the entire atrium floor opening were enclosed with a fire-rated shaft enclosure. This is because Section 1019.3 requires that floor openings containing exit access stairways or ramps that do not comply with one of the conditions listed in this section shall be enclosed with a shaft enclosure…” With Section 1019.3, condition 5, an exit access stairway can be placed in an atrium and the atrium need not be entirely enclosed; i.e., the atrium design can invoke Section 404.6, exception 3, to exempt any three floors from the enclosure requirement.

Section 1019.3, condition 5, says nothing about how many stories an exit access stairway can pass through before reaching an exit. Exit access stairways are still constrained by the limit in Section 1006.3.1 requiring that an exit access stairway to an exit shall not pass through more than one adjacent story.

It is possible for an unenclosed stairway in an atrium to pass through more than one adjacent story if it is defined as an interior exit stairway rather than as an exit access stairway. Section 1023.2, exception 2, of the 2018 IBC permits an interior exit stairway in an atrium to be constructed without enclosures consisting of fire barriers and/or horizontal assemblies. However, this exception applies only to the "construction" of an interior exit stairway and not to Section 1023.1 (General) or Section 1023.3 (Termination), which require that interior exit stairways shall "lead directly to the exterior of the building or shall be extended to the exterior of the building with an exit passageway" and "shall terminate at an exit discharge or a public way."

So, the bottom line is this: an unenclosed exit access stairway to an exit in an atrium can pass through no more than one adjacent story; an unenclosed interior exit stairway in an atrium can pass through any number of stories as long as it terminates at an exit discharge or public way.

Chris Campbell

6/27/2021 04:52:33 pm

Hi Jonathan,

Thanks for the detailed reply. I agree with many of your points, however the statement in my post regarding unlimited number of stories connected was really aiming at stairways within the atrium not used for egress.

But speaking to a stairway within an atrium that is used for egress - I agree with your thought process up until the end. If you have an exit stairway that connects multiple levels within the atrium, the stairway does have to take you to an exit discharge or be extended by an exit passageway. But there is nothing saying you can't use IBC 1028.1 Exception 1 to have the stairway send occupants through an area on the level of exit discharge such as a lobby. While the code would still deem this an interior exit stairway, from a construction/functionality standpoint, it is not really any different than an exit access stairway - both would be unenclosed and would require discharge through a lobby.

In my experience, the above example is used fairly frequently by architects with smaller atriums where the stair within the atrium can be still meet the 200' travel distance requirement.

Thanks again for the reply and let me know what you think!

Chris

6/27/2021 05:14:43 pm

I think my first reply disappeared, so I'll try again: We seem to agree on most points, but some clarification would still be useful. If you want your discussion of stairs in atriums to be about "convenience" stairs not used for egress, then your statement that "Open stairs in an atrium are permitted to serve as exit access stairways" is problematic, since an exit access stairway is part of a means of egress and therefore limited as I suggested.

In terms of unenclosed interior exit stairways terminating at the level of discharge, I agree that the exception in 1028,1 would probably allow a lobby at the level of discharge. What I was concerned about was the case of an atrium floor above the level of discharge (e.g., at the second floor), which is far more problematic in terms of 1023.2 exception 2.

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