Atrium and Open Exit access Stair (two distinct vertical openings) next to each other

[Blazer]

*Reference 2018 IBC*
Situation: Vertical opening with exit access stair is protected in accordance with condition #4 of 1019.3:

1. Sprinklered building
2. Area of opening is no more than 2x the projected area of stairs
3. Draft Curtain and closely spaced sprinklers
4. Connects 4 stories (Level 1-Level 4)

The code recognizes this form of protection as equivalent to shaft enclosure if I'm not mistaken.

Another vertical opening is in level 2 which connects Level 1 to Level 2. The two openings are a distance of 12 feet apart.

Drawings are not available since project is in development and not made public

Question: Is my code approach solid?
Code Approach: Can't I protect vertical openings with any of the 16 options available under 712.1. I have one opening protected in accordance with 712.1.12 Exit access stairways and ramps. The second opening (two openings in Level 2) will be protected in accordance with 712.1.7 Atriums. In section 403 it permits a two-story opening without smoke control (404.5) and without protection from adjoining spaces by fire barrier (404.6 #4). I have satisfied all methods of protection I believe and do not need to protect the second opening without a stair from the opening with the stair. The code does not mention that openings X feet apart shall be considered a single opening.

Also for consideration: The stair is huge so the opening is greater than 1,000 square feet. NFPA 13 Section 8.15.4.4 Large Openings states that closely spaced sprinklers and draft stops are not required. Further evidence I wouldn't need to protect the smaller opening in Level 2.

 

[RLGA]

I see where you are coming from, but I do not believe you are meeting the intent of the code. The two-story opening is atmospherically connected to the four-story opening. So, unless the two-story opening is separated from the four-story opening with 1-hour fire barriers, the aggregate area of the openings does not exceed two times the horizontal projection of the stairs, or all vertical openings are treated as a four-story atrium, I do not believe you will win your battle.

 

[Blazer]

I see where you are coming from, but I do not believe you are meeting the intent of the code. The two-story opening is atmospherically connected to the four-story opening. So, unless the two-story opening is separated from the four-story opening with 1-hour fire barriers, the aggregate area of the openings does not exceed two times the horizontal projection of the stairs, or all vertical openings are treated as a four-story atrium, I do not believe you will win your battle.

The opening is not atmospherically connected (term is used only when openings are not protected otherwise every interior exit stairway is "atmospherically connected" every time the doors are open and then wouldn't be permitted) to the four story opening because its protected with an equivalent shaft (a.k.a draft curtain and closely spaced sprinklers)

 

[RLGA]

The opening is not atmospherically connected (term is used only when openings are not protected otherwise every interior exit stairway is "atmospherically connected" every time the doors are open and then wouldn't be permitted) to the four story opening because its protected with an equivalent shaft (a.k.a draft curtain and closely spaced sprinklers)

Doors into exterior exit stairways do not mean the stairway is atmospherically connected to all of the stories.

Section 712.1.9 addresses two-story openings. I believe this section and the atrium section are at odds with each other. When exceptions for two-story atriums were introduced in the 2006 IBC, they did not take into consideration the two-story provisions in Chapter 7.

If you can convince your building department to accept your approach, congratulations. However, I doubt most building officials would approve it. As a consultant, I would advise my client against that approach unless one of those three options is implemented.

One thing to keep in mind is that stairways within openings provided per Section 1019.3, Condition 4, are not exit stairs. They are exit access stairs, so the path of egress can only pass through one adjacent story and not down the entire stairway (IBC Section 1006.3.1). This is to limit the use of the stairs since they are not as well-protected as exit stairways.