Help assessing if these corridors need to be rated.

[Ryan Schultz]

I'm working on a 5300sf unsprinklered, Type VB (B) & (S-1) Repair garage and car dealership.. The occupancy count is 49.

Question: per TABLE 1020.1, do the corridors needed to be rated for 1hr?

https://up.codes/viewer/wisconsin/ibc-2015/chapter/10/means-of-egress#table_1020.1

The corridor loads on the 1st floor are greater than 30 occupants so it looks like they need to be rated. If so, I'm assuming the corridors, highlighted in red, will need to be rated.

I question my assessment, however, since it's seems strange that such a small building would need rated corridors.

...

If the 1st floor corridors walls need to be rated, I'm assuming the ones on the mezznaine do not, as that corridor accommodates an occupant load less than 30.

pdf: https://www.dropbox.com/scl/fi/vbzd...FETY.pdf?rlkey=eod145padp6d3da6btrqdr11f&dl=1

 

[steveray]

30 people is the line last I checked...And 1 MOE in a B use....1020.2 exceptions...

 

[walker.t]

I'm assuming the corridors, highlighted in red, will need to be rated.

Not sure how the 2015 IBC defines “corridor,” but I would not have considered the area traced in red to a corridor, in this “corridor” you have occupied spaces (office, waiting area, and service desk,) it is not used exclusively for egress travel.

2021 IBC Definition of “Corridor” (emphasis added)
An enclosed exit access component that defines and provides a path of egress travel.

I'm assuming the ones on the mezznaine do not, as that corridor accommodates an occupant load less than 30.

Again, I would not consider the space you are referring to as a “corridor” to be a corridor because it is open to a space below that is not a corridor.

 

[Ryan Schultz]

Thanks @walker.t
As a thought exercise, what if that corridor didn't go through intervening spaces? That is the top sketch.

 

[walker.t]

what if that corridor didn't go through intervening spaces?

If the blue area in the top sketch is separated from the adjacent spaces with full-height walls (not partial height partitions) that enclose the area, it would be a corridor.

Back to your first post…

The corridor loads on the 1st floor are greater than 30 occupants so it looks like they need to be rated…I question my assessment…

Your assessment is correct that the corridor, because it has an occupant load greater than 30 in a non-sprinklered building, would need to have the 1-hour rating.

however, since it's seems strange that such a small building would need rated corridors.

It’s helpful to not think in terms of building size (area) but in number of occupants, and someone somehow determined that 30 occupants was as big as they thought it should be without a rated corridor or sprinklers.

the ones on the mezznaine

I’m not seeing anything on the second floor plan that looks like a mezzanine. Doesn’t really matter, you don’t have anything called out as a mezzanine so there shouldn’t be any confusion during plan review.

 

[Yankee Chronicler]

Most of what you have marked as corridor is corridor. I've circled in purple what I think is actually "corridor" as defined in the code:



I am concerned with the open stair as the only means of egress from the second story. The two remote corners are marked as 65 feet and 75 feet
common path of travel," but how is that measured and where does it terminate? An open stair is an exit access stair, so the exit access distance isn't measured to the bottom of the stair, it's measured to the exit door on the lower level. And at the stairs, the travel distance is measured along the line of the stair nosings, so you have to multiply the plan dimension by a factor of roughly 1.4 (depending on the rise:run ratio of the stair) to get the actual travel distance. I suspect you may not actually qualify for the second story to have only a single, open stair for egress.

 

[Ryan Schultz]

I believe the common path of travel is 100ft, for an unsprinklered S or B under 30 occupants.

https://up.codes/viewer/wisconsin/ibc-2015/chapter/10/means-of-egress#table_1006.2.1

I've measured the 'common path of travel' to the base of the stair, since from there, 2 exit paths are available to the occupant.

The exit access distance, i believe is 200ft, for an unsprinklered S or B.

https://up.codes/viewer/wisconsin/ibc-2015/chapter/10/means-of-egress#1017.2

 

[walker.t]

I believe the common path of travel is 100ft, for an unsprinklered S or B under 30 occupants.

Your link is to Table 1006.2.1 Spaces with One Exit or Exit Access Doorway. Does IBC 2015 have 1006.3 Egress From Stories or Occupied Roofs > Table 1006.3.4(2) Stories with One Exit or Access to One Exit for Other Occupancies? In the 2021 IBC, Table 1006.3.4(2) uses occupancy, maximum occupant load per story, and maximum exit access travel distance - not common path of egress travel like Table 1006.2.1. For B it is 49 occupants and 75’ exit access travel distance, S is 29 occupants and 75’ exit access travel distance.

I am concerned with the open stair as the only means of egress from the second story.

Nice catch.

 

[walker.t]

The exit access distance, i believe is 200ft, for an unsprinklered S or B.

Just noticed this link, it’s not opening a table for me, this might answer my question above about Table 1006.3.4(2) Stories with One Exit or Access to One Exit for Other Occupancies, I can’t view the page to confirm that myself.

 

[Yankee Chronicler]

I believe the common path of travel is 100ft, for an unsprinklered S or B under 30 occupants.

https://up.codes/viewer/wisconsin/ibc-2015/chapter/10/means-of-egress#table_1006.2.1

I've measured the 'common path of travel' to the base of the stair, since from there, 2 exit paths are available to the occupant.

The exit access distance, i believe is 200ft, for an unsprinklered S or B.

https://up.codes/viewer/wisconsin/ibc-2015/chapter/10/means-of-egress#1017.2

Second stories with a single means of egress are a special case. The common path of travel is overridden by the provisions governing stories with a single means of egress. The total exit access travel distance is limited to 75 feet.

 

[Ryan Schultz]

@Yankee Chronicler, @walker.t thank you for your perspectives.

I guess i was considering this a mezzanine, but i can see how maybe it would not qualify.

If it is considered a story, the 2015 table_1006.3.2-2 says Common Path of Travel.

https://up.codes/viewer/wisconsin/ibc-2015/chapter/10/means-of-egress#table_1006.3.2-2

 

[Yankee Chronicler]

But Wisconsin isn't on the 2015 IBC. According to UpCodes (which is where I copied the table I posted above), Wisconsin is on the 2021 IBC, and Table 1006.3.4(2) does NOT say Common Path of Travel.

From the 2021 IBC Commentary following Table 1006.3.4(2):



This seems pretty clear to me.

 

[Ryan Schultz]

Ugg, looks like it 'just' changed.

Thank you.

 

[Sifu]

It was apparently an editorial change that nobody wanted to talk about. I have not been able to find any official notice of the change

 

[LR419]

But Wisconsin isn't on the 2015 IBC. According to UpCodes (which is where I copied the table I posted above), Wisconsin is on the 2021 IBC...

But when I go to codes.iccsafe.org and choose Wisconsin as the location, it brings up the Oct. 2021 version of 2015 IBC. It looks like the enforcement date for the 2021 IBC has been deferred until November 1, 2025 (and reportedly now until April 1, 2026).
https://dsps.wi.gov/pages/Home.aspx
https://dailyreporter.com/2025/10/10/assembly-passes-bill-to-delay-commercial-building-code/

It's also rather confusing that there are separate tables for *spaces* and *stories* with a single means of egress. If a story contains only a single space, which table applies?

 

[Yankee Chronicler]

It's also rather confusing that there are separate tables for *spaces* and *stories* with a single means of egress. If a story contains only a single space, which table applies?

Both. The more restrictive requirement(s) govern(s).