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.

33 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.

Mohammed link

9/27/2021 03:42:59 pm

Hi Jonathan,

I am currently working on designing a residential apartment building and would like to obtain some clarity regarding IBC stairs requirements. The initial design includes 6 apartments with a ground floor for cars parking and on top of it 3 stories. 2 apartments per story. The building contains one enclosed stairs for means of egress. In this design, am I required to add one more stairs? is one stairs for means of egress sufficient and conforms to IBC? I think the building type is R2.

The lot area is small and adding one more stairs would sabotage the design.

Regards,
Mohammed

Hawk

11/7/2022 05:10:55 pm

Come on Jonathan... You do realize Section 1006.3.1 is that the path of egress travel (act of exiting) shall not pass through one adjacent story. This means that a person on level 3 must reach an exit (interior exit stairway) on level 2 and cant travel three stories to an exit thus meaning that the building will have at least one interior exit stairway. It doesn't mean the actual exit access stairway (structure/building element) cant transcend more than two stories. Also no such thing as unenclosed interior exit stairway. Class dismissed!

Chris Campbell

3/20/2023 02:45:26 pm

To close the loop on this, the 2021 IBC now specifically states in 1006.3.2 that the path of egress travel within an atrium is not limited to the adjacent story. I would agree though, Hawk, I think this was the intention all along.

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.

Ben Turner link

8/4/2021 04:27:31 pm

Can you explain how stairs can be open in relation to this code below (I added gaps at the pertinent section) :

1023.1 General. Interior exit stairways and ramps serving as
an exit component in a means of egress system shall comply
with the requirements of this section.
* Interior exit stairways and ramps shall be enclosed and lead directly to the exterior of the building or shall be extended to the exterior of the building *
with an exit passageway conforming to the requirements of Section 1024, except as permitted in Section 1028.1.
An interior exit stairway or ramp shall not be used for any
purpose other than as a means of egress and a circulation
path.

8/4/2021 04:59:44 pm

Interior exit stairs can be open — in the sense of not having enclosures constructed as fire barriers — based on the exceptions listed in Section 1023,2 (Construction). For example, exception #2 allows such stairs to forgo fire barrier enclosure when in an atrium, presumably because the atrium itself acts as a form of enclosure, per Section 404.6. But note that other provisions, e.g., Section 1023.3 (Termination), are NOT covered by this exception, so that such a stair would still need to terminate at an exit discharge or public way.

Timothy Arek link

9/16/2021 10:32:34 am

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9/27/2021 03:32:31 pm

Hi!

I am currently working on designing a residential apartment building and would like to obtain some clarity regarding IBC stairs requirements. The initial design includes 6 apartments with a ground floor for cars parking and on top of it 3 stories. 2 apartments per story. The building contains one enclosed stairs for means of egress. In this design, am I required to add one more stairs? is one stairs for means of egress sufficient and conforms to IBC? I think the building type is R2.

The lot area is small and adding one more stairs would sabotage the design.

Regards,
Mohammed

9/28/2021 03:11:17 pm

Yes, in principle, your project can be built with one stair. But be aware of the following (based on the 2018 IBC):

One exit is allowed (per Table 1006.2.1) if space has 20 or fewer occupants and maximum common path of egress travel does not exceed 125 feet. Also, you need sprinklers per 903.1.1 or 903.1.2.

Per Table 1006.3.3(1) Stories with one exit or access to one exit for R-2 occupancies: This applies to the basement, first, second, or third story above grade plane in R-2 (sprinklered) occupancies but you need to provide sleeping rooms with emergency escape and rescue openings per Section 1030: maximum of 4 du per floor and maximum 125 feet common path of egress travel distance.

Per Section 510.2, you can provide a horizontal assembly (fire-rated) to separate the garage from the R-2 occupancy above, and treat the R-2 stories as if they were floors 1, 2, and 3, thereby complying with Table 1006.3.3(1).

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10/14/2021 12:02:37 am

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10/14/2021 12:02:51 am

Maritza Hawthorne

10/20/2021 11:00:29 am

Hello,
We are currently designing a 2 story restaurant with a 4 story attached parking garage. We plan to have 2 open air stairs that would provide egress for the parking garage, however one of those stairs is currently also acting as secondary egress from the restaurant. So patrons that are on the 2nd floor of the restaurant have direct access to the parking garage and directly adjacent to that access is the egress stair that at this point would serve as egress for both parking garage and the 2nd floor of the restaurant. Is this allowed by code?

10/20/2021 11:11:15 am

Hi Maritza,

Please shoot me an email and I can try and assist:

chris (at) buildingcode (dot) blog

Thanks!

Chris

Charlie Calvano

12/17/2021 10:34:54 am

I would like to confirm that this open stair connecting three or more stories can only apply if the stair is not being used as a means of egress, unless it meets the requirements of Section 1006.3.1 which states "The path of egress travel to an exit shall not pass through more than one adjacent story." This tells me that there has to be an enclosed stairway nearby meeting the Exit Access Travel Distance from each floor to the adjacent floor below. The code commentary also outlines that exit access stairs open to multiple floors is allowed to be all the way down for multiple levels, specifically noting Exception 2, 3, 6, 7, and 8 in Section 1019.3. Exception 4 is not noted. So it appears very limited.

1/11/2022 08:47:46 am

Hi Charlie,

That's correct, the exit access travel distance does not end at the exit access stairway, it has to be measured to an exit. So yes, if you are using an exit access stair to serve three or more stories, you do effectively need another exit nearby that is within the travel distance limits. This could be a exit stairway, or potentially a horizontal exit.

One thing to keep in mind is that the travel distance only has to be met to a single exit. So if your plan meets the travel distance requirements to an exit stairway, an exit access stairway could be used to provide additional egress capacity from a given story while still being "open".

John Campbell

1/21/2022 08:54:13 am

Does a 2-story, open, exit access stairway create an Atrium condition? Our design includes an open stair joining large, public spaces on two stories. Since the code allows this without an enclosure, our understanding was that this is not an Atrium and we have not provided any of the Atrium-related provisions in Chapter 4. However the code official reviewing the project claims our open stair has created an Atrium condition, and therefore wants the entire perimeter of our large, open spaces on each floor to have a 1-hour rating as would be required around the perimeter of a more traditional atrium. Can you shed any light on this? Thank you!

1/21/2022 09:18:50 am

Historically, most code officials have taken your interpretation, that a two story opening complying with IBC 712.1.9 would not need to comply with the atrium provisions of IBC 404. This positions has further been clarified in the 2021 IBC, which now specifically defines an atrium as connecting three or more stories, except in certain Group I occupancies.

1/21/2022 09:22:50 am

An exit access stairway opening can be designed either as an atrium, or as a two-story opening per Section 1019. If you comply with the Section 1019 criteria (basically that the opening communicates between only two stories, and is not open to other stories), then it need not be designed as an atrium. This is explained in Section 712, where the various protection methods for vertical openings are listed. These are alternative protection methods, and the intention is to find one that works, not to apply more than one protection method to a single vertical opening.

RKM

10/10/2022 11:28:29 am

CAN YOU INCLUDE A HANDICAPPED LIFT SHAFT ADJACENT TO UNENCLOSED EXIT ACCESS STAIRS DISCHARCHING OUTSIDE THRU A NARROW LOBBY. THIS AN EXISTING TWO STORY OFFICE BUILDING. THERE IS A SECOND EXISTING ENCLOSED EXIT STAIR SERVING THE BUILDING.

Lhynzie link

2/10/2022 01:19:25 am

Amazing design. I love the idea of having a glass open stairs at home. thank you for sharing these photos and designs.

Maria

2/24/2023 01:58:57 pm

I have an exit access stair running along the side of a big "seating stair" (informal stepped hangout space) that connects two levels. The actual exit access stair is only 8' wide whereas the whole "seating stair" area is about 30' wide.

I don't understand enough about the fire spread dynamics behind the floor opening size restriction in 1019.3.4 to know if it makes sense to argue that the stepped seating area should be considered as equivalent to the exit access stair in terms of calculating the maximum floor opening size. That is -- that the "seating stair" is functioning like the exit access stair with respect to the hole in the floor.

I could imagine arguments in both directions. Theoretically I could build all 38' wide as an actual exit access stair by adding some intermediate treads + risers to our big chunky seating steps, and that would be allowed. So does it really make it less safe if some of that width is seating steps, as long as overall the building is providing sufficient egress capacity?

2/24/2023 03:15:25 pm

I'm not sure that exception 4 in 1019.3 is scientifically rigorous (having the allowable open area set at exactly twice the horizontal projected area of the exit access stair) but the intention of the rule seems clear, since such openings create a vertical opening (shaft) that permits the spread of smoke, hot gases, etc. I would therefore conclude that your stepped seating would be counted as being "in" the opening, rather than making the opening smaller, since it would not prevent the spread of smoke and gas vertically. Your argument that it is in some ways equivalent to making the stair wider may be true, but the code is not always that nuanced. Remember that having any vertical opening is already a compromise in terms of fire safety, so I wouldn't try to interpret this exception as allowing something that is probably less safe rather than trying to design something that is more safe.

Figari Group link

3/28/2023 06:16:08 am

Thank you for giving me an idea about open stairs in an office, amazing designs.

Manon

4/1/2023 06:24:53 pm

Hi Chris,
We own 2 units over floors 2,3,4 of a NYC 5 stories townhouse. We are planning to combine 2 units into one . So that at the end of it the building will be two dwellings R3. Right now we have an interior stair and an exterior one but in combining the 2 units we will keep only one. And we would like to keep an open design around the stairs without enclosure. The big question is can we keep the stairs open and also renovate under a prior code? The 1968 code seem to say that stairs within a dwelling allow for that exception but the language is hard to ascertain. Thank you for any tips on how to confirm this,

Splashbacks nz link

4/4/2023 06:42:09 am

Such a nice blog on Requirements for Open Stairs and I hope you keep update us with such great tips and information in future too. This is a great post; I will share as much as I can.

Aaron D

4/12/2023 02:23:56 pm

Would it be code compliant to have a 3 story exit access stairway for a B occupancy as 1 of the 2 required means of egress (1 hr stair shaft for the 2nd) if utilizing the draft curtain exception 1019.3 #4? Or would 1006.3.1 still prevent this for the path of egress travel passing through more than one adjacent story?

4/12/2023 04:18:52 pm

Aaron,

In my opinion, as long as you can meet the travel distance limitations for the occupancy involved, 1006.3.1 would not preclude that arrangement.

Chris

Cedric

4/25/2023 04:03:16 pm

We have an interconnecting stair (not used as means of Egress) between two floors. It is penetrating a two-hour floor assembly but we have an enclosure on the upper floor (3 sides of 2HR rated glass and 4th side is D400 drop smoke curtain).

Would we still need a draft curtain on the lower floor around the stair opening?

Naj

5/26/2023 11:18:15 pm

Hi,
I am working on a residential (R-2) building where I have 2 compliant exits (enclsoed stairs). I also have a convenient open stair connecting 3 stories at the public corridors. is there a way to make the open stair compliant or must I keep it enclosed?
Can I use draft curtain and closely spaced sprinklers?

Thank you,

Gerson R.

6/19/2023 12:16:07 pm

On an open stair as means of egress. Where does one measure the stair separation? To center to the stair run or stair opening? In a enclose stair, one measured to the center of the door, but what about an open stair.

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8/7/2023 03:25:36 am

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