# High-Rise Communicating Stair



## HVACQuestions (Sep 23, 2019)

HVAC designer here, I'm working on a job with an existing high rise tower with a communicating stair connecting 2 floors. The architect wants to cut another hole in the ceiling to have this stair connect 3 floors. I'm trying to figure out any mechanical implications of them doing so; is there a section of the IBC that governs fire protection/smoke concerns with communicating staircases? I thought it had to do with the size of the stair opening.


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## RLGA (Sep 23, 2019)

Which code edition year is applicable and what occupancy group is using the stairway?


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## HVACQuestions (Sep 23, 2019)

RLGA said:


> Which code edition year is applicable and what occupancy group is using the stairway?



I'm going off of IBC 2015, occupancy group B


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## cda (Sep 23, 2019)

Welcome


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## RLGA (Sep 23, 2019)

This would be an exit access stairway per Section 1019. You may be able to use Section 1019.3, Condition 4, as an option. If not, then the stairway will need to be enclosed,


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## HVACQuestions (Sep 23, 2019)

RLGA said:


> This would be an exit access stairway per Section 1019. You may be able to use Section 1019.3, Condition 4, as an option. If not, then the stairway will need to be enclosed,



Even though this stair is not a path of egress?


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## HVACQuestions (Sep 23, 2019)

cda said:


> Welcome


Thanks!


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## RLGA (Sep 23, 2019)

HVACQuestions said:


> Even though this stair is not a path of egress?


All stairways are part of an egress path whether intended or not. Openings between floors must comply with the requirements of Chapter 7 and it will have exceptions or conditions specific for egress elements per Chapter 10.


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## HVACQuestions (Sep 23, 2019)

RLGA said:


> All stairways are part of an egress path whether intended or not. Openings between floors must comply with the requirements of Chapter 7 and it will have exceptions or conditions specific for egress elements per Chapter 10.



Interesting. So a communicating stair that is not intended to be of use for egress, still has to comply with this section? It surprises me that this isn't handled similarly to an escalator opening.


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## Tim Mailloux (Sep 23, 2019)

HVACQuestions said:


> Interesting. So a communicating stair that is not intended to be of use for egress, still has to comply with this section? It surprises me that this isn't handled similarly to an escalator opening.



I was under assumption that an unenclosed communicating stair which is not part of the egress system (exit access stair) is handled similar to an escalator.


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## RLGA (Sep 23, 2019)

Start first in Section 712 for vertical openings. It does have requirements for escalators—but escalators only. Other options in this section for this specific application include enclosing it in a shaft, making it an atrium, or making it an exit access stairway.


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## steveray (Sep 24, 2019)

Ron has it....An opening with a stair in it is not always egress, but it is always a hole in the floor...And may or may not need to be protected....


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## Tim Mailloux (Sep 24, 2019)

Wouldn't section 712.1.9 Two story openings apply to this situation?


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## cda (Sep 24, 2019)

Tim Mailloux said:


> Wouldn't section 712.1.9 Two story openings apply to this situation?




“””The architect wants to cut another hole in the ceiling to have this stair connect 3 floors“””


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## steveray (Sep 24, 2019)

Yep...2 story is easy if no other "holes" to other floors...


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## Tim Mailloux (Sep 24, 2019)

cda said:


> “””The architect wants to cut another hole in the ceiling to have this stair connect 3 floors“””



I missed that part. Looks like the stair either needs to be classified as an atrium or an access stair. An access stair will be cheaper than an atrium (smoke control) as long as the travel distances will work.


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## tbz (Sep 25, 2019)

Interesting Topic, but I have another question on this topic as to location.


So currently there is a communicating stair from lets say 4th floor to the 5th floor.  

Now lets say on the other side of the office space, not in the same location now wants to install a 2nd communicating stair from the 5th floor to the 6th floor, but neither stair flight or opening are in the same visual sight line, but open air will travel from one area to another.
does this change anything since they are 2 different stair flights and not stacked?


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## RLGA (Sep 25, 2019)

Compliance with 712.1.9 is required. Two-story openings are permitted, but item #6 of that section requires openings serving other stories to be separated by fire-resistive construction as required for shafts. Thus, since the two openings would technically connect three stories, then a 1-hour fire barrier is required on the 5th story somewhere that would completely separate the two openings from one another. If the floor assemblies are required to be of 2-hour construction or more, then the fire barrier separating the two openings must have a fire-resistance rating of 2 hours.


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## steveray (Sep 27, 2019)

Yep...Especially problematic in existing buildings where there may be nonprotected HVAC  and other "shafts".....


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## Builder Bob (Sep 27, 2019)

Look at the technical report of MGM  Fire - majority of fire fatalities was from smoke inhalation and not thermal or fire due to the ability of the smoke to easily transfer to the higher floors when the fire originated in the lobby/1st floor area.


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## Tim Mailloux (Oct 10, 2019)

As luck would have it, I was just asked to help out on a tenant fit our project in an existing type 1A high rise building (26 stories) with 2 hour rated structure and floors. The tenant will occupy two floors in the building and wants to add an open communicating stair between the two floors, this stair will not be part of the egress system. Section 712.1.9 Two Story openings applies to this situation, but item #2 has me thinking:


_#2 Does not penetrate a horizontal assembly  that separates fire areas  or smoke barriers that separate smoke compartments._




Wouldn’t each floor be an individual fire area, and wouldn’t cutting an opening be penetrating the horizontal assembly?


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## RLGA (Oct 10, 2019)

Fire areas are only necessary to determine the application of a sprinkler system within a building or portion of a building. Since high rise buildings are required to be sprinklered anyway, the fire area requirements are moot.


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## JPohling (Oct 11, 2019)

Tim Mailloux said:


> As luck would have it, I was just asked to help out on a tenant fit our project in an existing type 1A high rise building (26 stories) with 2 hour rated structure and floors. The tenant will occupy two floors in the building and wants to add an open communicating stair between the two floors, this stair will not be part of the egress system. Section 712.1.9 Two Story openings applies to this situation, but item #2 has me thinking:
> 
> 
> _#2 Does not penetrate a horizontal assembly  that separates fire areas  or smoke barriers that separate smoke compartments._
> ...


That should not be an issue at all............except perhaps for any existing smoke control.


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