Rooftop stair wall/door rating

[chris macko]

IBC 2021- Type 1B building, 2 stories with a non-occupied roof. The roof has a lot of equipment on it, so we have a few stairs going up there with doghouses along the perimeter. The stairs have 3 exterior walls below, and the 1 interior wall is inline with the building perimeter. The roof is rated 1 hour, the interior stair wall is 2 hours, and the stair sidewalls are 1 hour per 1023.7. The question I have right now is does the roof facing wall and door need to be rated at the roof level, or is it just considered an exterior wall so no rating is needed? The roof itself is 1 hour (concrete slab, concrete topping), so I think it complies with the intent of 1023.7, but that section specifically says walls, not horizontal surfaces. Since the roof is unoccupied, it's not technically an exit, it's just an access stair, but the stair is an exit from the second floor below.

 

[walker.t]

Having trouble understanding what you are trying to describe, do you have a plan view of the roof showing the stairs?

the 1 interior wall is inline with the building perimeter

Huh? An “interior wall” in line with the building perimeter - wouldn’t that make it an exterior wall?

or is it just considered an exterior wall so no rating is needed?

So you’re thinking it doesn’t have to be rated because it’s a nonbearing wall per Table 601?

Since the roof is unoccupied

If this is an interior exit stairway I don’t think you can use this for access to the roof per 1023.4:

2021 IBC 1023.4 Openings (emphasis added)
Openings in interior exit stairways and ramps other than unprotected exterior openings shall be limited to those required for exit access to the enclosure from normally occupied spaces and for egress from the enclosure.

 

[chris macko]

It's an enclosed stair tower directly adjacent to the building, so there is one shared wall between them that is in plane with the building exterior. It's a 3 story mass stuck to a 2 story mass. It's an exterior non-bearing wall, so 601 points to 705.5, but in this case since it's a stair enclosure, I'm thinking it falls under 1023.7 since it's an exterior wall of an interior stair. It's still an enclosed stair, so I'm considering it interior, not exterior. The stair roof, building roof, and steel framing are still rated to 1 hour because of 601.

1023.4 is interesting because it seems to specifically exclude "unprotected" openings to the exterior. Having an interior egress stair go to the roof or using it as a location for a roof hatch is extremely common in multi-story buildings, so I would be shocked to find that wasn't allowed by code.

 

[steveray]

IBC 2021- Type 1B building, 2 stories with a non-occupied roof. The roof has a lot of equipment on it, so we have a few stairs going up there with doghouses along the perimeter. The stairs have 3 exterior walls below, and the 1 interior wall is inline with the building perimeter. The roof is rated 1 hour, the interior stair wall is 2 hours, and the stair sidewalls are 1 hour per 1023.7. The question I have right now is does the roof facing wall and door need to be rated at the roof level, or is it just considered an exterior wall so no rating is needed? The roof itself is 1 hour (concrete slab, concrete topping), so I think it complies with the intent of 1023.7, but that section specifically says walls, not horizontal surfaces. Since the roof is unoccupied, it's not technically an exit, it's just an access stair, but the stair is an exit from the second floor below.

So the roof/ building is potentially a threat to the exit enclosure (90 degrees or <180 anyway) but not any other part of the building? Is that your question?

 

[chris macko]

Yes, 1023.7 allows for adjacent exterior walls to be rated 1hr within 10ft of the stair, but does not mention roofs or horizonal surfaces. My question is if the 1 hour roof meets this separation requirement, or if the 2 hour shaft rating needs to continue up past the building roof even though it's an exterior wall.

 

[walker.t]

It's an enclosed stair tower directly adjacent to the building

Thank you, that’s a helpful clarification, so you’re doing something basically like this (but bigger and with more stairs):


The yellow wall is the “roof facing wall and door” you mentioned in your first post.

 

[chris macko]

Yes, it's exactly like that

 

[steveray]

Not super well addressed in code but I think I would accept the 1 hour roof sort of like a stepped building...

Hey it is in 2024 IBC:

1023.7.2Roof assemblies.​

Where the interior exit stairway or ramp extends above an adjacent roof of the same building, the adjacent roof assembly shall have a fire-resistance rating of not less than 1 hour and openings shall be protected by opening protectives having a fire protection rating of not less than 3/4 hour. The fire-resistance rating and opening protection shall extend horizontally not less than 10 feet (3048 mm) from the exterior wall of the stairway or ramp, or to the perimeter of the adjacent roof, whichever is less.

Exceptions:

1. 1.
   The roof assembly need not be rated and openings in the roof need not be protected where they are adjacent to the penthouse of the stairway or ramp, unless otherwise required by this code.
2. 2.
   The adjacent roof assembly need not be rated and adjacent openings in the roof need not be protected where the exterior wall of the stairway or ramp has a fire-resistance rating of 1 hour and openings are protected by opening protectives having a fire protection rating of not less than 3/4 hour, extending not less than 10 feet (3048 mm) above the roof.

 

[steveray]

But really if it qualifies as a penthouse you can do nothing....

 

[chris macko]

Just to close the loop on this, I finally got a chance to look at the commentary and it does address this condition. It points to table 705.8.6 for exterior vertical exposure. That section has an exception where if the roof is rated within 10ft of the wall, the wall is not required to be rated.

 

[steveray]

Just to close the loop on this, I finally got a chance to look at the commentary and it does address this condition. It points to table 705.8.6 for exterior vertical exposure. That section has an exception where if the roof is rated within 10ft of the wall, the wall is not required to be rated.View attachment 16300View attachment 16301

Nope...look at ex #2....