Nosing projection & Open Risers

[tbz]

So nosing projections are limited to 1 1/4" and or the degree angle.

however 1011.5.5.3 (VA 2015 IBC) Solid risers are required for all M.O.E. stairs, however when not a M.O.E. stair, then open risers are allowed per exception 1.

But the exception does not note the limit of the 1 1/4" nosing max.

Thus the question, does the stair tread that slides under the tread above required to terminate no more than 1 1/4" under the tread, or are you allowed to have the tread under the one above extend further.

In a solid riser flight, the solid riser would limit the distance under the tread above, when that riser is not required to be there, how does that effect the tread below?

Your thoughts?

 

[e hilton]

If the stair falls under exception 1, then the nosing projection is a moot point. There is nothing from which to measure the “projection”.

 

[mark handler]

WITH OR WITHOUT A RISER, MEASURE TO BACK OF LOWER TREAD

 

[tbz]

WITH OR WITHOUT A RISER, MEASURE TO BACK OF LOWER TREAD

View attachment 6990

Mark,

Were did you pull this diagram from?

So your understanding and or position is that the tread that goes under the tread above is measured to the rear of the tread even with no solid riser, correct.

My question is, do you know the reasoning to hold that position when there is no riser? Is it not safer to make sure a foot does not extend through and thus, is it not better to have more tread/landing behind?

And what do you do when you get to floor level under the bottom tread? How do you have an open risers and at the same time not extend the floor beyond the 1-1/4?

Thanks for posting the pic Mark.

So 1 vote exempt and 1 vote to the back of the tread.

more input would be great.

Regards - Tom

 

[Builder Bob]

Open risers still have to prohibit the passage of a four inch sphere so in a 7 inch riser, you would have a barrier to measure the nosing distance from...

 

[tbz]

Open risers still have to prohibit the passage of a four inch sphere so in a 7 inch riser, you would have a barrier to measure the nosing distance from... View attachment 6996

Bob,

The project is only 6" risers with a 2-1/2" thick tread, thus only a 3-1/2" open riser, which meets the 4" sphere requirement.

My question is simply on open risers does the maximum nosing depth apply or not? and if it does, how does one treat mid landings and bottom landings under the last tread.

The other option is that the maximum nosing depth does not apply were solid risers are not required per the IBC and or IRC.

Thank you for chiming in

 

[mark handler]

Mark,
Were did you pull this diagram from?
So your understanding and or position is that the tread that goes under the tread above is measured to the rear of the tread even with no solid riser, correct.
My question is, do you know the reasoning to hold that position when there is no riser? Is it not safer to make sure a foot does not extend through and thus, is it not better to have more tread/landing behind?
And what do you do when you get to floor level under the bottom tread? How do you have an open risers and at the same time not extend the floor beyond the 1-1/4?
Thanks for posting the pic Mark.
So 1 vote exempt and 1 vote to the back of the tread.
more input would be great.
Regards - Tom

it is a modified, off the internet, picture.
I added the text. There is nothing in the code, that i know of, that exempts a tread in a nonsolid riser stair, from the noising requirement.

 

[e hilton]

Builder ... exception 1 notes the 4” sphere but exception 3 does not, so it reads that the 4” sphere does not apply to spirals.

 

[Paul Sweet]

2015 IBC 1011.5.2 says tread depth is measured from nosing to nosing.

I don't see why a tread in an open riser stair can't extend farther than 1 1/4" back from the nosing. In fact, 1011.15.2 allows a 3 1/2" projection in a ship's ladder. I'm not sure what the 1 1/4" limit of 1011.5.5.1 is for, other than a greater projection might cause a disabled person's foot to get caught. ADASAD 504.5 allows a 1/2" projection.

 

[ADAguy]

"Big" tRip hAZARD: Consider that those with "big" feet may catch their toes if there is no limit to the overhang.

 

[tbz]

ADAGuy,

I get the whole trip thing and the big foot under the tread as a reason for requiring a nosing within a MOE, but once you remove the solid riser requirement and enlarge the opening to the 4 inch sphere, there should be an exception for the nosing requirement IMO, but gather the not there there.

Thanks for the response...

 

[Paul Sweet]

" "Big" tRip hAZARD: Consider that those with "big" feet may catch their toes if there is no limit to the overhang. "

Even if the tread ends 1 1/4" beyond the nosing above, somebody can still stick their big feet far enough beyond the end of the tread to trip if there's no riser to stop them.