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High-Rise Communicating Stair

H

HVACQuestions

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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.
 
Which code edition year is applicable and what occupancy group is using the stairway?
 
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,
 
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,
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Even though this stair is not a path of egress?
 
HVACQuestions said:
Even though this stair is not a path of egress?
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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.
 
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.
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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.
 
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.
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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.
 
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.
 
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....
 
cda said:
“””The architect wants to cut another hole in the ceiling to have this stair connect 3 floors“””
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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.
 
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?
 
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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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?
 
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.
 
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.




Wouldn’t each floor be an individual fire area, and wouldn’t cutting an opening be penetrating the horizontal assembly?
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That should not be an issue at all............except perhaps for any existing smoke control.
 
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