Auditorium allowable differences in Riser height

[m.r.scott2u]

trying to get some clarification.
on riser heights in an auditorium with ramped aisles. In the ramp run where there is 3 sets of steps that have 2 risers and 1 tread. About 10 feet apart. The ramp is at allowable grade. So in the stepped aisles section 1030.14. 14.2.2 exception 1 states that where nonuniformities exceed 3/16" between adjacent risers a distinctive marking stripe needs to be used. So to me risers that differ in height, more that 3/16" are allowable if they are marked. My question is, up to what difference? Can you have one riser at 4" and the next one at 5-1/2"? as long as the distinctive marking stripe is in place, or bigger? clearly over 3/16" difference in riser height is allowed but up to what ?

 

[Gregg Harris]

trying to get some clarification.
on riser heights in an auditorium with ramped aisles. In the ramp run where there is 3 sets of steps that have 2 risers and 1 tread. About 10 feet apart. The ramp is at allowable grade. So in the stepped aisles section 1030.14. 14.2.2 exception 1 states that where nonuniformities exceed 3/16" between adjacent risers a distinctive marking stripe needs to be used. So to me risers that differ in height, more that 3/16" are allowable if they are marked. My question is, up to what difference? Can you have one riser at 4" and the next one at 5-1/2"? as long as the distinctive marking stripe is in place, or bigger? clearly over 3/16" difference in riser height is allowed but up to what ?

Exception: The tolerance between adjacent treads shall not exceed 3/16 inch (4.8 mm)

Shall not exceed

 

[Yankee Chronicler]

trying to get some clarification.
on riser heights in an auditorium with ramped aisles. In the ramp run where there is 3 sets of steps that have 2 risers and 1 tread. About 10 feet apart. The ramp is at allowable grade. So in the stepped aisles section 1030.14. 14.2.2 exception 1 states that where nonuniformities exceed 3/16" between adjacent risers a distinctive marking stripe needs to be used. So to me risers that differ in height, more that 3/16" are allowable if they are marked. My question is, up to what difference? Can you have one riser at 4" and the next one at 5-1/2"? as long as the distinctive marking stripe is in place, or bigger? clearly over 3/16" difference in riser height is allowed but up to what ?

Each set of 2 risers and one tread is a "flight." The exception states:



Technically, the language of the code seems to allow what you are describing. From a practical standpoint, I can't imaging designing multiple flights of steps, each of which has one 4" riser and one 5-1/2" riser. The exception says that nonuniform risers shall be permitted "to the extent necessitated by changes in the gradient of the adjoining seating area." Is the slope of the seating area really so screwed up that it necessitates this much difference between the heights of two adjacent risers in a set if steps?

 

[e hilton]

I think he said the steps are 10 ft apart.

 

[Yankee Chronicler]

I think he said the steps are 10 ft apart.

That's not how I read it.

there is 3 sets of steps that have 2 risers and 1 tread. About 10 feet apart.

I interpret that to mean a set of 2 risers and one tread, then a gap of ten feet, then another set of 2 risers and one tread.

 

[bill1952]

The code allows "Riser height nonuniformity shall be limited to the extent necessitated by changes in the gradient of the adjoining seating area to maintain adequate sightlines."

If you said each successive riser increased by say a 1/4" for sight lines, I'd say it was allowable. If I were a building official, I'd ask you for a sightline drawing to prove it was necessary. As a theatre designer, having done thousands of sightlines drawings, I know that you don't understand sightlines.

I can't imagine how you could possibly justify what you describe. I can assure you it would cause more fall injuries than if uniform risers. I could imagine steps every 10' or so serving tiers of seats - like dinner theatre or stadium restaurants - but the ramp between them is bewildering. And I think I can safely say a 1 1/2" difference in adjacent riser heights is never necessary for sightlines.

And by the way, the landings at top and bottom of each set of stairs, has to be level, not ramped, for depth equal to width of stairs. Combining ramped and stepped aisles while meeting code and achieving sightlines is about the most difficult assembly seating design I have done and gotten constructed correctly.

And those stairs or stepoed aisles - are they serving seating or are they connecting ramped aisles?

Happy to review at no cost if you message me and want to share a drawing.

 

[Yankee Chronicler]

I can't imagine how you could possibly justify what you describe. I can assure you it would cause more fall injuries than if uniform risers. I could imagine steps every 10' or so serving tiers of seats - like dinner theatre or stadium restaurants - but the ramp between them is bewildering. And I think I can safely say a 1 1/2" difference in adjacent riser heights is never necessary for sightlines.

The fall injuries issue was one of my first thoughts when I read the question. There are a lot of things that building codes may technically allow but which absolutely should not be done, because they're likely to result in fall injuries. And when those injuries occur, the designers are among the cast of thousands who will be sued.

 

[bill1952]

The fall injuries issue was one of my first thoughts when I read the question. There are a lot of things that building codes may technically allow but which absolutely should not be done, because they're likely to result in fall injuries. And when those injuries occur, the designers are among the cast of thousands who will be sued.

I'm very particular to the point of sometime driving my architect clients a little crazy. Yes and inch matters. Yes I know you can claim a handrail exception but why when you don't need to? And don't get me started on equivalent sightlines for wheelchair spaces, acknowledging it's subtle and costs money. All part of what I call floorplate management.

 

[Yankee Chronicler]

I'm very particular to the point of sometime driving my architect clients a little crazy. Yes and inch matters. Yes I know you can claim a handrail exception but why when you don't need to? And don't get me started on equivalent sightlines for wheelchair spaces, acknowledging it's subtle and costs money. All part of what I call floorplate management.

Yeah. Ask Cinemark about sightlines ...

Or Ellerbe Beckett ...

 

[e hilton]

Can you give a quickie explanation for designing sight lines?

 

[bill1952]

Sure. In morning. Some good diagrams in A117.1 but will be better in next edition.

Careful what you ask for - I could do a semester long course on it

 

[m.r.scott2u]

That's not how I read it.



I interpret that to mean a set of 2 risers and one tread, then a gap of ten feet, then another set of 2 risers and one tread.

You are correct

 

[m.r.scott2u]

Each set of 2 risers and one tread is a "flight." The exception states:

View attachment 16277

Technically, the language of the code seems to allow what you are describing. From a practical standpoint, I can't imaging designing multiple flights of steps, each of which has one 4" riser and one 5-1/2" riser. The exception says that nonuniform risers shall be permitted "to the extent necessitated by changes in the gradient of the adjoining seating area." Is the slope of the seating area really so screwed up that it necessitates this much difference between the heights of two adjacent risers in a set if steps?

It's not an 1-1/2" difference in riser height, I was saying that as an example, over 3/16" is allowable if you add a distinctive stripe, is how I read it, my question was to how much over that. given that even with sight lines and the low grade ramp, the 1 step should be made 1/2 the distance of those 2 risers, but it wasn't.

 

[e hilton]

That's not how I read it.



I interpret that to mean a set of 2 risers and one tread, then a gap of ten feet, then another set of 2 risers and one tread.

That’s what i said.

 

[Yankee Chronicler]

It's not an 1-1/2" difference in riser height, I was saying that as an example, over 3/16" is allowable if you add a distinctive stripe, is how I read it, my question was to how much over that. given that even with sight lines and the low grade ramp, the 1 step should be made 1/2 the distance of those 2 risers, but it wasn't.

I'm sorry, but I have no idea what this means.

You started this discussion by asking if a variation of 1-1/2 inches in riser height in a run is allowable with the warning stripe. Now you're saying that the difference isn't really an inch and a half -- but you haven't said what it is. You also haven't told us if this is a new design you're working on, or if you are trying to analyze an existing condition to assess code compliance. It's very difficult to respond with any useful information when the question is so nebulous.

How about explaining exactly what the problem is? Then perhaps we can offer some applicable opinions.

 

[bill1952]

or a photo?

 

[jc_ks]

I'm sorry, but I have no idea what this means.

You started this discussion by asking if a variation of 1-1/2 inches in riser height in a run is allowable with the warning stripe. Now you're saying that the difference isn't really an inch and a half -- but you haven't said what it is. You also haven't told us if this is a new design you're working on, or if you are trying to analyze an existing condition to assess code compliance. It's very difficult to respond with any useful information when the question is so nebulous.

How about explaining exactly what the problem is? Then perhaps we can offer some applicable opinions.

To me this reads like a hypothetical situation. The answer to his question I think was given: 'The only difference allowed in risers is that needed for sightlines, and sightlines would not require a 1.5" difference in risers.'