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run vs tread

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sunyaer

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Toronto
The following is from Ontario Building Code, Division B, Part 3:
--------------------------------------------------------------------------------------------------------------
3.3.2.4. Aisles
...
(23) Steps in an aisle shall,
(a) have a run not less than 230 mm exclusive of nosings,
(b) have a tread depth not less than 250 mm,
(c) extend to the adjacent rows of seats in a manner that will not create a hazard from tripping, and
(d) have a finish on the treads conforming to Sentence 3.4.6.1.(1)
...
-------------------------------------------------------------------------------------------------------------
Is "run" the same thing as "tread" in clause (b) above? If yes, why are they specified in separate clause?
 
I'm guessing not same thing, but are they defined. They are both way less than IBC requires, and hazardous in my opinion.

Seems one - 230 - is the nosing to nosing and the other - 250 - is riser to nosing.
 
This is from Ontario Building Code, Division B, Part 3 too:
-------------------------------------------------------------------------------
3.3.2.10. Bleachers
(1) Steps provided in aisles of bleachers of the telescopic type shall,
(a) have risers not more than 250 mm high, and
(b) have treads with a run not less than 280 mm.
-------------------------------------------------------------------------------
Here the code says "treads with a run", does a tread equal the run plus nosing?
 
In that last drawing, what is labeled "tread depth" should be labeled "run". The tread depth should be the full depth of a tread, from the front edge of the nosing back to the face of the riser above. The drawing shows that tread depth is greater than the run by the nosing overhang. If the risers aren't plumb, that will also contribute to a difference between run and tread depth.

Cheers, Wayne
 
wwhitney said:
In that last drawing, what is labeled "tread depth" should be labeled "run". The tread depth should be the full depth of a tread, from the front edge of the nosing back to the face of the riser above. The drawing shows that tread depth is greater than the run by the nosing overhang. If the risers aren't plumb, that will also contribute to a difference between run and tread depth.

Cheers, Wayne
Click to expand...
You're probably right, because we concern ourselves with rise and run most, but it's not defined that way in the IBC now and would only create chaos to try and change it. It does seem like the OBC defines them as you suggest.
 
bill1952 said:
it's not defined that way in the IBC now and would only create chaos to try and change it.
Click to expand...
Interesting, my comments were just based on the OP, the difference in terminology used in the quoted code section, and common sense. I hadn't realized from that point of view that the IRC/IBC is misusing the term "tread depth" when it should be using the term "run." On the other hand, if the true "tread depth" is never regulated by the IRC/IBC, and only the "run" is regulated, there's no internal conflict caused by the IRC/IBC choice of definition.

So when I said in what is labeled "tread depth" in the diagram should be labeled "run," I meant for purposes of the code quoted in the OP. Apparently the diagram is correctly labeled for the IRC/IBC.

Cheers, Wayne
 
This is 2021 IBC - italics mine:

1011.5.2 Riser height and tread depth.​

Stair riser heights shall be 7 inches (178 mm) maximum and 4 inches (102 mm) minimum. The riser height shall be measured vertically between the nosings of adjacent treads or between the stairway landing and the adjacent tread. Rectangular tread depths shall be 11 inches (279 mm) minimum measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread’s nosing. Winder treads shall have a minimum tread depth of 11 inches (279 mm) between the vertical planes of the foremost projection of adjacent treads at the intersections with the walkline and a minimum tread depth of 10 inches (254 mm) within the clear width of the stair.

I don't disagree that the IBCs tread depth is the run. Pretty sure this is an amalgamation of the legacy building codes developed for the 1985 BCMC MOE report, the basis for chapter 10 of the first edition of the IBC.
 
treads and risers are different than Rise and Run no matter how the code splits the hairs. I use the following diagramed figure when explaining the theory to inspectors, designers and fabricators.

The bottom line is the enforced area is rise and run, call it what ever you want.

Treads and Risers.JPG
 
tbz said:
no matter how the code splits the hairs
Click to expand...
Need to be a little more specific when the OP is asking about the OBC, not the IBC. But I'd agree as far as IBC is concerned.

That right-hand part with sloped treads is one where the first and/or last rise are often not uniform with the other risers. And now I've gone further off the topic of the OBC.
 
sunyaer said:
The following is from Ontario Building Code, Division B, Part 3:
--------------------------------------------------------------------------------------------------------------
3.3.2.4. Aisles
...
(23) Steps in an aisle shall,
(a) have a run not less than 230 mm exclusive of nosings,
(b) have a tread depth not less than 250 mm,
(c) extend to the adjacent rows of seats in a manner that will not create a hazard from tripping, and
(d) have a finish on the treads conforming to Sentence 3.4.6.1.(1)
...
-------------------------------------------------------------------------------------------------------------
Is "run" the same thing as "tread" in clause (b) above? If yes, why are they specified in separate clause?
Click to expand...
Run means the horizontal distance between two adjacent tread nosings on a stair (nosing to nosing).

Tread depth is the measurement from nosing to the riser of the next step (nosing to riser).
 
Joe.B,

The cut patter for the stringer rise and run if you trace the cut except for the bottom tread will lay over the top rise and run.

In either case nosing to nosing.

I once had an hour-long discussion with an architect in Europe on how "Tread Depth" = "Riser Height", and as his vodka kept being poured, he explained that depth was a vertical measurement and not a horizontal one.

The way I see it, depth is a distance in any direction............but then again I didn't have any vodka to back it up with.
 
Remember, in NBC Run is a defined term.

Run means the horizontal distance between two adjacent tread nosings on a stair. (See
Figure A-9.8.4.-B in Note A-9.8.4. of Division B.)
 
Inspector Gadget said:
Remember, in NBC Run is a defined term.

Run means the horizontal distance between two adjacent tread nosings on a stair. (See
Figure A-9.8.4.-B in Note A-9.8.4. of Division B.)
Click to expand...
Which is probably the reason the International codes use
R311.7.5.1 Risers​
R311.7.5.2 Treads​
and not Rise and Run

[RB] RISER (STAIR). The vertical component of a step or stair.
[RB] FLIGHT. A continuous run of rectangular treads or winders or combination thereof from one landing to another.
 
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