Ok, I'm working on a winding tread layout (for R-3 occupancy), and am finding it quite a headache/challenge to design within the ICB parameters (1009.3), at least as I understand them. This is how I am interpreting them:
1) Minimum tread depth at the narrowest portion of the tread is 6", measured perpendicular to the tread's edge.
2) The "Walk line" is 12" in from this 6" minimum depth.
3) This 12" distance is measured along the outside edge of the tread.
4) Minimum tread depth at the walk line (measured along the tread's edge) is 10", measured perpendicular to the tread's edge.
5) Per 1009.3.2 (Dimensional uniformity), none of the winder treads can differ from each other at the walk line tread depth more than .375", again measured perpendicular to each tread's edge.
The stair design is a "U", where there are rectangular treads and then a full U-turn.
Is there some calculation I can use to figure out this layout, or do I just have to keep moving lines around by fractions of an inch until it comes out right??
yeah you just kind of have to work it out .. it's pretty fast these days with all the auto-caddin' software out there.
since all your winder treads will be the same then you just need to divide up that area into 3 winder treads, 4, etc. and check where you are at the 12" walk line. you won't be '... moving lines around by fracitons of an inch' since your winder treads will be equal.
basically as the straight-run (parallel) stairs get further apart you can fit more winder treads since they need that 6" minimum tread depth .. that's the trade off with putting in more winder treads.
the 1009.3.2 section is to allow for a little contractor imperfection during construction.
I wasn't sure whether or not my suggestion had any merit. So, this morning while I had some free time and put it to the test:
It works! So segmented arcs may provide some ease. The only big trouble I had were the first and last steps which don't seem to usually match up with the linear approaches.
Alternately: 2007 CA building code and 2007 IRC have more clear guidelines for drawing spiral stairs for R-3:
Min. tread width: 26"
Max Riser: 9.5"
Min tread depth at 1'-0" radius from it's inner edge: 7.5"
given these parameters, I lay out my outer boundary of the winder staircase (square or circle) and make concentric circles originating from the center out and lay 7.5" line segments tangent to the 1'0" radius guide.
Jun 10, 10 1:28 am ·
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Winding stair tread design
Ok, I'm working on a winding tread layout (for R-3 occupancy), and am finding it quite a headache/challenge to design within the ICB parameters (1009.3), at least as I understand them. This is how I am interpreting them:
1) Minimum tread depth at the narrowest portion of the tread is 6", measured perpendicular to the tread's edge.
2) The "Walk line" is 12" in from this 6" minimum depth.
3) This 12" distance is measured along the outside edge of the tread.
4) Minimum tread depth at the walk line (measured along the tread's edge) is 10", measured perpendicular to the tread's edge.
5) Per 1009.3.2 (Dimensional uniformity), none of the winder treads can differ from each other at the walk line tread depth more than .375", again measured perpendicular to each tread's edge.
The stair design is a "U", where there are rectangular treads and then a full U-turn.
Is there some calculation I can use to figure out this layout, or do I just have to keep moving lines around by fractions of an inch until it comes out right??
yeah you just kind of have to work it out .. it's pretty fast these days with all the auto-caddin' software out there.
since all your winder treads will be the same then you just need to divide up that area into 3 winder treads, 4, etc. and check where you are at the 12" walk line. you won't be '... moving lines around by fracitons of an inch' since your winder treads will be equal.
basically as the straight-run (parallel) stairs get further apart you can fit more winder treads since they need that 6" minimum tread depth .. that's the trade off with putting in more winder treads.
the 1009.3.2 section is to allow for a little contractor imperfection during construction.
Hmm-- well, to find the absolute minimum (or smallest) according to code...
[6" * 12 (number or treads I'm assuming) * 2 (the first two figures are for a half circle) ] / pi
= diameter of 3' 9 13/6"
If i use a segmented arc, every segment will give me my minimum 6 inch tread width with 10" at 12" walk line.
previous winding stair discussion on archinect
some really, really good stairs (not suitable for residential):
.jpg)
Niemeyer (concrete with carpet designating tread space)
Jacobsen (steel, floating)
Eliel Saarinen
Hey I just found this great site - its proper spelling is being blocked: http://www.stairp*rn.org/
Great, thanks to all for the help. And jobbyjob, very cool website.
I wasn't sure whether or not my suggestion had any merit. So, this morning while I had some free time and put it to the test:
It works! So segmented arcs may provide some ease. The only big trouble I had were the first and last steps which don't seem to usually match up with the linear approaches.
Alternately: 2007 CA building code and 2007 IRC have more clear guidelines for drawing spiral stairs for R-3:
Min. tread width: 26"
Max Riser: 9.5"
Min tread depth at 1'-0" radius from it's inner edge: 7.5"
given these parameters, I lay out my outer boundary of the winder staircase (square or circle) and make concentric circles originating from the center out and lay 7.5" line segments tangent to the 1'0" radius guide.
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