Open-ended corridors - 2018 IBC

[TXTrailRunner]

Trying to solve an issue on my apartment project regarding exterior stairs with open-ended corridors.
2018 IBC. Construction Type V-A, Group R-2. Four stories. NFPA 13 sprinkler system.
The building plan is very simple. Double loaded corridor with a stair at each end. No change of direction in the corridor.

It appears from Section 1027.6, exception 3 that no separation is required between the stairs and the open-ended corridor.
The corridors are 1-hour rated, so my assumption is that the 1-hour rating would also apply to the stair itself.
Normally an interior exit stair would have a 2-hour rated enclosure for 4 stories, but this is an exterior stair by definition, and I do not see any requirement in Section 1027 that addresses the rated walls at the stair in this situation.
Also, it does not make sense to me that the rating at the stair would be higher than the corridor if there is no separation between the two.
Wondering if anyone has dealt with this issue before?

 

[RLGA]

Section 1027.6.

 

[RLGA]

Sorry for the short answer, but I just realized you were already in Section 1027.6. You do not need to separate the exterior stairs from the corridor, but you still need to protect the stairs from the interior of the building per Section 1027.6.

 

[steveray]

I think I understand what you are saying and the short answer is the exceptions let you out of the section (sort of)

1027.6​

Exterior exit stairways and ramps shall be separated from the interior of the building as required in Section 1023.2. Openings shall be limited to those necessary for egress from normally occupied spaces. Where a vertical plane projecting from the edge of an exterior exit stairway or ramp and landings is exposed by other parts of the building at an angle of less than 180 degrees (3.14 rad), the exterior wall shall be rated in accordance with Section 1023.7.

So you comply with 1023.2 for the separation rating until you go to the exceptions and here is where it is poorly written:

Exceptions:

1. 1.Separation from the interior of the building is not required for occupancies, other than those in Group R-1 or R-2, in buildings that are not more than two stories above grade plane where a level of exit discharge serving such occupancies is the first story above grade plane.
2. 2.Separation from the interior of the building is not required where the exterior exit stairway or ramp is served by an exterior exit ramp or balcony that connects two remote exterior exit stairways or other approved exits with a perimeter that is not less than 50 percent open. To be considered open, the opening shall be not less than 50 percent of the height of the enclosing wall, with the top of the openings not less than 7 feet (2134 mm) above the top of the balcony.
3. 3.Separation from the open-ended corridor of the building is not required for exterior exit stairways or ramps, provided that Items 3.1 through 3.5 are met:
   
   3.1.The building, including open-ended corridors, and stairways and ramps, shall be equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2.
   3.2.The open-ended corridors comply with Section 1020.
   3.3.The open-ended corridors are connected on each end to an exterior exit stairway or ramp complying with Section 1027.
   3.4.The exterior walls and openings adjacent to the exterior exit stairway or ramp comply with Section 1023.7.
   3.5.At any location in an open-ended corridor where a change of direction exceeding 45 degrees (0.79 rad) occurs, a clear opening of not less than 35 square feet (3.3 m2) or an exterior stairway or ramp shall be provided. Where clear openings are provided, they shall be located so as to minimize the accumulation of smoke or toxic gases.
4. 4.In Group R-3 occupancies not more than four stories in height, exterior exit stairways and ramps serving individual dwelling units are not required to be separated from the interior of the building where the exterior exit stairway or ramp discharges directly to grade.

Exception 3 seems to almost indicate that you only have to meet 1023.7 not 1023.2 and there is your 2 hour or 1 hour swing....My take would be Ex 3 is just allowing the corridor to be open to the stair and the stair still needs 2hr separation from the rest of building....

 

[TXTrailRunner]

I think I understand what you are saying and the short answer is the exceptions let you out of the section (sort of)

1027.6​

Exterior exit stairways and ramps shall be separated from the interior of the building as required in Section 1023.2. Openings shall be limited to those necessary for egress from normally occupied spaces. Where a vertical plane projecting from the edge of an exterior exit stairway or ramp and landings is exposed by other parts of the building at an angle of less than 180 degrees (3.14 rad), the exterior wall shall be rated in accordance with Section 1023.7.

So you comply with 1023.2 for the separation rating until you go to the exceptions and here is where it is poorly written:

Exceptions:

1. 1.Separation from the interior of the building is not required for occupancies, other than those in Group R-1 or R-2, in buildings that are not more than two stories above grade plane where a level of exit discharge serving such occupancies is the first story above grade plane.
2. 2.Separation from the interior of the building is not required where the exterior exit stairway or ramp is served by an exterior exit ramp or balcony that connects two remote exterior exit stairways or other approved exits with a perimeter that is not less than 50 percent open. To be considered open, the opening shall be not less than 50 percent of the height of the enclosing wall, with the top of the openings not less than 7 feet (2134 mm) above the top of the balcony.
3. 3.Separation from the open-ended corridor of the building is not required for exterior exit stairways or ramps, provided that Items 3.1 through 3.5 are met:
   
   3.1.The building, including open-ended corridors, and stairways and ramps, shall be equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2.
   3.2.The open-ended corridors comply with Section 1020.
   3.3.The open-ended corridors are connected on each end to an exterior exit stairway or ramp complying with Section 1027.
   3.4.The exterior walls and openings adjacent to the exterior exit stairway or ramp comply with Section 1023.7.
   3.5.At any location in an open-ended corridor where a change of direction exceeding 45 degrees (0.79 rad) occurs, a clear opening of not less than 35 square feet (3.3 m2) or an exterior stairway or ramp shall be provided. Where clear openings are provided, they shall be located so as to minimize the accumulation of smoke or toxic gases.
4. 4.In Group R-3 occupancies not more than four stories in height, exterior exit stairways and ramps serving individual dwelling units are not required to be separated from the interior of the building where the exterior exit stairway or ramp discharges directly to grade.

Exception 3 seems to almost indicate that you only have to meet 1023.7 not 1023.2 and there is your 2 hour or 1 hour swing....My take would be Ex 3 is just allowing the corridor to be open to the stair and the stair still needs 2hr separation from the rest of building....

That's where the logic seems to break down to me. I can easily design a 2hr wall that separates the stair from the adjacent apartments on either side of the stair, but where does the 2hr wall transition to the 1hr corridor if there is no separation between the two? It seems arbitrary. In my opinion this section of the code needs more clarification to make sense. I even read the IBC Commentary on this section, and it made it even more confusing.

Thanks for the reply.

 

[steveray]

That's where the logic seems to break down to me. I can easily design a 2hr wall that separates the stair from the adjacent apartments on either side of the stair, but where does the 2hr wall transition to the 1hr corridor if there is no separation between the two? It seems arbitrary. In my opinion this section of the code needs more clarification to make sense. I even read the IBC Commentary on this section, and it made it even more confusing.

Thanks for the reply.

Well we can go back to no open corridors....That will make it clearer....

 

[TXTrailRunner]

Well we can go back to no open corridors....That will make it clearer....

Hopefully I can get a read from the AHJ before I get too deep into the details