Fire rated stair case within the common path of egress travel distance

[Ana]

So I'm on a second floor of a B use group, and my occupant load is less than 29 on the 2nd floor. The building is fully sprinklered, and I'm allowed to go up to 100 feet for my common path of egress ((per IBC 2018 1006.3.3 (2). There's only one fire rated stair case going from the 2nd floor to the first floor as part of my egress path. My question is, do I have to add the distance traveled within the stair case as part of the common path of egress before we have the option to go in two ways to the other exits on the first floor? For some reason, I feel I've seen somewhere in the code that you can stop calculating the distance at the stair door (at the top level) if the stair enclosure is fire rated, or is only my dream ?

 

[classicT]

It depends on what type of stair you have. And it also depends on if you are asking about exit access travel distance or common path of egress travel distance (CPET)

If it is an Exit Access Stairway, you include the travel along the stairway in measuring the exit access travel distance as per IBC Section 1017.3.1 (below). If it is an Interior Exit Stairway, you stop the measurement at the doorway. Interior Exit Stairways are fire rated and have enhanced requirements - see IBC Section 1027.

Noting that in your question, you asked about CPET, take note of Section 1006.2.1. Given that your OL is less than 30 and that you reach an exit in less than 100-ft, you are ok herein.

However, you must also consider Section 1006.3.4... specifically Table 1006.3.4(2). From this table, you will determine the maximum OL and maximum exit access travel distance for a story with a single exit or exit access stairway.

1006.2.1 Egress Based on Occupant Load and Common Path of Egress Travel Distance​

Two exits or exit access doorways from any space shall be provided where the design occupant load or the common path of egress travel distance exceeds the values listed in Table 1006.2.1. The cumulative occupant load from adjacent rooms, areas or spaces shall be determined in accordance with Section 1004.2.

Exceptions: (not included here)​

1017.3.1 Exit Access Stairways and Ramps​

Travel distance on exit access stairways or ramps shall be included in the exit access travel distance measurement. The measurement along stairways shall be made on a plane parallel and tangent to the stair tread nosings in the center of the stair and landings. The measurement along ramps shall be made on the walking surface in the center of the ramp and landings.

 

[e hilton]

I’m going through a similar situation for the lower level of a branch reno. Below grade, no windows or doors to the exterior. My AoR has a PE on staff who is their fire protection lead, and this is his determination for our situation.

 

[Ana]

I’m going through a similar situation for the lower level of a branch reno. Below grade, no windows or doors to the exterior. My AoR has a PE on staff who is their fire protection lead, and this is his determination for our situation.

So in your situation, your stair is an open stair that is not enclosed, so the circulation through the stair was considered as part of the maximum common path of egress, but my question is: if the stair is enclosed completely with a fire rated enclosure, then do you consider the circulation through that fire rated enclosure as part of the common path of egress? or do you stop at the fire rated enclosure door?

 

[classicT]

...if the stair is enclosed completely with a fire rated enclosure, then do you consider the circulation through that fire rated enclosure as part of the common path of egress? or do you stop at the fire rated enclosure door?

By definition of CPET, you would never include an interior exit stairway in the measurement. Once you reach an exit, the CPET ends.

[BE] COMMON PATH OF EGRESS TRAVEL. That portion of exit access travel distance measured from the most remote point of each room, area or space to that point where the occupants have separate and distinct access to two exits or exit access doorways.

[BE] EXIT ACCESS. That portion of a means of egress system that leads from any occupied portion of a building or structure to an exit.

[BE] EXIT. That portion of a means of egress system between the exit access and the exit discharge or public way. Exit components include exterior exit doors at the level of exit discharge, interior exit stairways and ramps, exit passageways, exterior exit stairways and ramps and horizontal exits.

CPET simply does not pertain in this scenario. The more restrictive requirement is that found in Table 1006.3.4(2). You may have a single means of egress pathway and single exit where complying with said table.

 

[Ana]

By definition of CPET, you would never include an interior exit stairway in the measurement. Once you reach an exit, the CPET ends.

[BE] COMMON PATH OF EGRESS TRAVEL. That portion of exit access travel distance measured from the most remote point of each room, area or space to that point where the occupants have separate and distinct access to two exits or exit access doorways.

[BE] EXIT ACCESS. That portion of a means of egress system that leads from any occupied portion of a building or structure to an exit.

[BE] EXIT. That portion of a means of egress system between the exit access and the exit discharge or public way. Exit components include exterior exit doors at the level of exit discharge, interior exit stairways and ramps, exit passageways, exterior exit stairways and ramps and horizontal exits.

CPET simply does not pertain in this scenario. The more restrictive requirement is that found in Table 1006.3.4(2). You may have a single means of egress pathway and single exit where complying with said table.

That makes sense! Thanks so much!

 

[bill1952]

separate and distinct access to two exits or exit access doorways.

How do you stop measuring CEPT at a single exit access door when the definition says two?

 

[Paul Sweet]

IBC 1023.1 requires an exit stair to discharge directly to the outside or through an exit passage (except for exceptions in 1028.1). If your enclosed stair does not meet this it is part of the exit access and you have to include the distance inside the stair along the nosing line.

 

[JPohling]

just when do these people have access to two distinct exits or directions?

 

[bill1952]

just when do these people have access to two distinct exits or directions?

My point. The CPET is measured till you have the chouce of two separate means if egress. 2 ways out. That would IMHO include a single stair - exit stair or open.

 

[steveray]

It's a little gray, but CT has it in post 5....there is no exit access measurement when you are in an exit....

 

[classicT]

It's a little gray, but CT has it in post 5....there is no exit access measurement when you are in an exit....

Appreciate that we may be like-minded on this one.

To clarify, my thought process is that per 1006.2.1, the requirement is that where the CPET values in Table 1006.2.1 are exceeded, two exits are required. Given that an exit is reached in less than the prescribed distance, two exits are not required - keep in mind that reaching an interior exit stairways is nearly equivalent to reaching an exterior exit door. For example, if you have an open building with a single entry/exit doorway, and all points are within the CPET distance limit, you would not require a second entry/exit doorway. For basic purposes, a CPET does not really exist, because a single exit is a permitted condition.

1006.2.1 Egress Based on Occupant Load and Common Path of Egress Travel Distance​

Two exits or exit access doorways from any space shall be provided where the design occupant load or the common path of egress travel distance exceeds the values listed in Table 1006.2.1.

[BE] COMMON PATH OF EGRESS TRAVEL. That portion of exit access travel distance measured from the most remote point of each room, area or space to that point where the occupants have separate and distinct access to two exits or exit access doorways.

[BE] EXIT ACCESS. That portion of a means of egress system that leads from any occupied portion of a building or structure to an exit.

[BE] EXIT. That portion of a means of egress system between the exit access and the exit discharge or public way. Exit components include exterior exit doors at the level of exit discharge, interior exit stairways and ramps, exit passageways, exterior exit stairways and ramps and horizontal exits.

IMHO, what really matters, is Table 1006.3.4(2). The story, having a single exit, must comply with the maximum exit access travel distance identified herein, which is a more restrictive provision. A second exit, and thus a CPET, is required/measured/meaningful when the value of Table 1006.3.4(2) is exceeded. Where this occurs, a second exit is required - thus it is possible to measure the CPET.

 

[bill1952]

Appreciate that we may be like-minded on this one.

To clarify, my thought process is that per 1006.2.1, the requirement is that where the CPET values in Table 1006.2.1 are exceeded, two exits are required. Given that an exit is reached in less than the prescribed distance, two exits are not required - keep in mind that reaching an interior exit stairways is nearly equivalent to reaching an exterior exit door. For example, if you have an open building with a single entry/exit doorway, and all points are within the CPET distance limit, you would not require a second entry/exit doorway. For basic purposes, a CPET does not really exist, because a single exit is a permitted condition.



IMHO, what really matters, is Table 1006.3.4(2). The story, having a single exit, must comply with the maximum exit access travel distance identified herein, which is a more restrictive provision. A second exit, and thus a CPET, is required/measured/meaningful when the value of Table 1006.3.4(2) is exceeded. Where this occurs, a second exit is required - thus it is possible to measure the CPET.

Does that require you remain in an exit stair or passage all the way to the exit discharge, as Paul Sweet mentioned above?

 

[classicT]

Does that require you remain in an exit stair or passage all the way to the exit discharge, as Paul Sweet mentioned above?

Yes. If it is an interior exit stairway, that is covered in 1023.3 (below).

1023.3 Termination​

Interior exit stairways and ramps shall terminate at an exit discharge or a public way.

Exception: A combination of interior exit stairways, interior exit ramps and exit passageways, constructed in accordance with Sections 1023.2, 1023.3.1 and 1024, respectively, and forming a continuous protected enclosure, shall be permitted to extend an interior exit stairway or ramp to the exit discharge or a public way.​

 

[max8176]

I have similar situation in my current project and I am confused with what is the CPET and Exit Access Travel. Can I eliminate ST04 and just maintain ST03 with one exit out of the basement? Occupancy is under 29 and fully sprinklered.

 

[steveray]

I have similar situation in my current project and I am confused with what is the CPET and Exit Access Travel. Can I eliminate ST04 and just maintain ST03 with one exit out of the basement? Occupancy is under 29 and fully sprinklered.

View attachment 12860

I think your blue line would have to be <75'...1006.3.4 (2)..But you might get an increase to 100'

 

[max8176]

I think your blue line would have to be <75'...1006.3.4 (2)..But you might get an increase to 100'

Yes, correct, 100 feet when fully sprinklered. Unfortunate, with the current configuration I would be over the 100 feet limit.

 

[steveray]

Yes, correct, 100 feet when fully sprinklered. Unfortunate, with the current configuration I would be over the 100 feet limit.

Only in B, F, and S occupancies do you get the increase to 100.....So be careful...

 

[max8176]

Only in B, F, and S occupancies do you get the increase to 100.....So be careful...

I only have storage spaces and maintenance office in the basement. But look like I am exceed of the 100' limit, right?

 

[steveray]

I only have storage spaces and maintenance office in the basement. But look like I am exceed of the 100' limit, right?

yes

 

[Yankee Chronicler]

So in your situation, your stair is an open stair that is not enclosed, so the circulation through the stair was considered as part of the maximum common path of egress, but my question is: if the stair is enclosed completely with a fire rated enclosure, then do you consider the circulation through that fire rated enclosure as part of the common path of egress? or do you stop at the fire rated enclosure door?

The answer is, "It depends."

The stair may be enclosed in a rated shaft and have compliant fire doors at the top and bottom, but does the stair discharge directly to the exterior or meet one of the exceptions for exit discharge through areas on the level of exit discharge? If not -- then it isn't an "exit" and the exit access travel distance has to include the stair and the path of discharge from the stair to the actual exit.