Winder Treads on a Monumental Stair

[MKALLAY]

I looked to see if this issue has been discussed previously, but I do not see that it has been - apologies of this repeats a prior discussion!

I am looking at a project where a monumental stair is proposed (A3 occupancy). The project will be governed by 2021 IBC. The proposed stair is not a required means of egress in that it can be eliminated and all required egress from the upper level will still be served. The stairway has a directional change that uses winder treads.

I see that IBC 1011.5.3 indicates “winder treads are not permitted in means of egress stairways except within a dwelling unit.” An exception is given for curved stairways in accordance with Section 1011.9.

1011.9 requires that “the smallest radius shall be not less than twice the minimum width or required capacity of the stairway.” Since this stair has no required occupant load, I would assume that the 36” minimum width would apply (so 6’-0” Radius)

But what I am questioning is - if the stairway is not a required MOE, would winder treads that comply with the dimensional requirements of 1011.5.2 be permitted, without need to apply the minimum radius of a curved stairway? Or is it the intent of the Code that 1011.9 should apply to any stairway serving occupied areas?

I am leaning in this case toward the first case but wondering what others here have come up with.

 

[steveray]

1011.1​

Stairways serving occupied portions of a building shall comply with the requirements of Sections 1011.2 through 1011.13.

To start the debate.....

 

[MKALLAY]

1011.1​

Stairways serving occupied portions of a building shall comply with the requirements of Sections 1011.2 through 1011.13.

To start the debate.....

Yes, I often quote that passage to our staff! And I would say "end of debate", if 1011.5.3 did not insert the phrase "in means of egress stairway" - which seems to me intended to qualify that this specific requirement is conditional...

 

[steveray]

I mightbe able to get on board with that being specific vs. general...

[A]102.1​

Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall be applicable. Where, in any specific case, different sections of this code specify different materials, methods of construction or other requirements, the most restrictive shall govern.

 

[Yankee Chronicler]

Where would there be a monumental stairway that is not at the main entrance to a building, and where would the main entrance not also be a means of egress?

 

[MKALLAY]

Where would there be a monumental stairway that is not at the main entrance to a building, and where would the main entrance not also be a means of egress?

The project in question is a large state assembly building. the levels in question are at the 5th and 6th floor, with assembly rooms on the 5th floor and public galleries on the 6th. A central lobby space has a floor opening connecting these two levels. In consideration would be a stairway connecting the two levels in the lobby. There is no direct exit to grade here other than through the required enclosed exit stairways. (1/2 of the exit stairs discharge through the main level lobby as permitted by 1028.2)

 

[Yankee Chronicler]

We regard all stairs/stairways that might be used by an occupant as a means of egress as being within the purview of Chapter 10. The provision you quoted from section 1011.5.3 says "means of egress stairways," it does not say "stairways designated as required means of egress."

 

[MKALLAY]

Thanks all, for the feedback. My role in the process is advisory, with no authority as far as enforcement goes; but I have advised the designer that they should consider that the curved stairway limitations may apply. It's always best to take the conservative approach, IMO!