2018 IBC - Section 1029.17.4 Guards at the end of aisles ( North Texas above Dallas)

[tbz]

So here is the question I will try to explain as the drawings are still on the way which have a clearer layout hopefully than those attached.

• New Church Choir Loft
  • side aisle at ends
  • So this loft is 1 level up and what is going on is this, the main area in purple on the first PDF is a 42 in high glass guard, need only be 26 for sightline but they installed 42 as it is glass, the yellow area is up one riser and is at 36 inches with a top bar added to extend to 42.
  • The owner is claiming that the front of the end aisles marked in yellow, what I will call landings because you turn to step down again to the lower level, only needs to be 36" high not 42, per 1029.17.4 of the 2018 IBC.
  • Part of it might be able to claim 1029.17.3 sightline as I drew red lines were I would think you would call sightline, but the front of aisles are not the end per how we interpret this section..
  • I drew an outline in blue for what I believe is the seating area in the choir loft and possible sightline in red.
  • I also included a second pdf to show a cut view of the guard at the bottom of the aisles, in yellow.
• So the position the fabricator is taking, erroring on the safe side is that per 1029.17.4 this exception only applies to the side of the aisle, not the front at the turn, at the landing for the following reasons
  • The second sentence of 1029.17.4 Guards at end of aisles "The fascia or railing shall be not less than 36 inches (914 mm) high and shall provide not less than 42 inches (1067 mm) measured diagonally between the top of the rail and the nosing of the nearest tread."
    • So this section has always confused me, as the vertical rise will always be longer than the parallel line of the nosing run, which is pitched. Thus if the 42" is diagonal from the tread's nosing line to 42, the vertical rise is going to be more than 42.
    • The reason they want to leave the ends 36" is because this lines up with the 42 inches of the purple area as you go across.
• So how would you interpret the guard height requirement for this situation.
  • We believe it needs to be 42" because it is not within the sightline, nor on the sides of a descending end aisle, the owner is saying 36" it only needs to be 36 and wants the metal bar removed from the top.
  • The other issue is the metal bar design does not comply, as the 2018 IBC only allows 4.375 in opening from 36-42, that is another bridge to cross once this is settled.

Look forward to hearing from you all.

Regards - Tom

 

[bill1952]

Having dealt with this detail in a hundred or so buildings and in code committee meetings and hearings for over 30 years, I could draw it faster than explain it in words.

The guard at the fascia where you show yellow as well as the section at end of first row and for the width of the aisle along the front all is required to be min 36" aff or higher per aisle stair nosings. I'm not understanding the floor elevations, but despite what looks like treads I am guessing one 6" rise per row. The 42" is measured in section and I usually draw 42" radius arcs to see if the guard at foot of aisle needs to be more than 36.

If it's 36 above 2nd row and 42 above first all the way across, I believe it's fine for code (but will suck for some one in first row and probably second.)



I and many other theatre consultants would say your sight lines in plan are too limited. It's about everyone in the seating seeing everyone in the choir loft and on the platform. But I don't think that will matter or change anything.

If it would help, contact me at bcaworld.com, just bill at. Or I can try to sketch and post here tomorrow.

 

[steveray]

I think I would agree with the 36" height in the yellow area....

 

[bill1952]

While the section title says "end of aisles" the requirement says "foot of the aisle" which I think accurately describes the yellow section parallel with the rows of seats as well as the purple section not in front of seating.

The "sightline-constrained" section is only in front of seating, and does not apply to the foot of aisles.

I can't be sure where the first step is before hitting the foot of aisle guard, but suspect 3' or more from it in all 4 locations. If the rows were 18" elevation change and there were 2 intermediate steps, a 3' row would have 3 risers of 6" just a foot apart and a foot from the guard. When you measure 42" from that last nosing the guard is likely required to be more than 42" above the row level.

In attached sketch suspect the top view is like yours but the bottom is a more typical balcony aisle condition. Top shows 36" is OK while bottom shows guard over 3' 10" measured vertically.

Trouble posting sketch from phone. Working on it.

 

[bill1952]

Sorry - I can't figure out how to attach a pdf here and not finding help.

 

[bill1952]

https://imgur.com/L0I5eSx

I think that will get you sketch. Don't understand this site nor imgur - first and only post there. Sorry for my ineptitude at this.

 

[tbz]

Bill,

Thanks for the sketches, posting pic's is tough if you are not a paid member of the forum. I used to put them in my media folder on my website and direct the forum to the linked location, until I joined the paid percentage.

Anyway, back on target, It would be much simpler if the title was foot, not end.

My takeoff has the face of nosing at 24 inches and the riser 6", which calc's out to just under 40.5"

Thanks again for the clarification.

 

[bill1952]

So 36 at foot of further out side aisle is not enough. If really fixated on the level top all the way - something anyone not privy to this discussion would ever notice imho - you might tilt or cantilever the top rail out.

Unrelated, without knowing more about plan, what appears to be narrowing side aisle to 24" could be of concern. Don't know what OL is and type of seating.

Assembly occupancy and guards and rails and m.o.e. are not simple. Just consider that of 7 guard exceptions, 5 apply only to assembly. Aisle stair rules are much different than ordinary stairs.

 

[tbz]

So I have received a picture on the project, which will provide a better understanding of what is there on site.

The area in question is the doorway level area where the double stack 2x4' go from the drywall corner column to the wall.

Thus based on this information is that area considered an end of isle and subject to the lower 36" height, or since seating area is directly behind it, though one level up, treated differently?

 

[bill1952]

It could go either way - a full 42" guard or 36" foot of aisle. If I were the theatre consultant on this project, I think I would urge the 42". I'm concerned by the choir standing - likely close to rail - and less concerned by the sightlines of choir members seated behind it. They will be poor - or non existant, and those people can use the video screens. In many projects I would expect to see a monitor mounted on the rail or high over it these days.

But I think at least the Life Safety Code would permit 36", and likely IBC, and believe I have justified it in similar situations. If you want to make it 36 to align with 42" in first row but want a little more protection, put a horizontal projection on face of vertical - a rail like a towel bar 8 to 12" out. The combined height and width is nearly as effective as the same dimension all heigth. I became aware of that research before computers and internet, so hard to put my fingers on.

Generally turns in assembly seating aisles are very hard to solve and usually avoided. I'd prefer that people entered, immediately turned right along wall to the head of an aisle that goes all the way to first row, but not possible now. Less fall hazard and better sightlines. In general cross aisles at a balcony fascia should be avoided like the plague for multiple reasons.

 

[tbz]

Here is a plan view I just got...to add

 

[bill1952]

I predict a lot of stumbles at that 1' 1/4" wide step down. I'd expect the choir will put tape or glow tape or other markings on it in first week. BTW the IBC and LSC both require a contrasting marking at all nosings in assembly aisle stairs. I'd fill it in and be sure there was a graspable hand rail at that riser from row 1 to 2. or pull what looks like a low horizontal rail on seating side of foot of aisle and have it project far enough so no one and stumble on that short right angle riser.

 

[bill1952]

Sorry, haven't found edit for posts. I meant to add having that horizontal projection would kill 2 birds - block the short nosing and make the 36" high rail safer.