Confusion with Code interpretation for "Curved" winders vs Spiral

[John_B]

I'm trying to help a GC understand this drawing (not mine) because I believe that it is not code compliant...when I try to draw this in Chief it won't allow such a tight radius and when I look at the code, it appears that at the "walking line" which is defined as 12" from inner radius, the tread should be 10" minimum....am I missing something here?

[ACADuser]

Your walk line is at 2'-5". If you measure the tread at 12" out front the inner radius the tread will be less than 10".

That's my best guess.

I'm nut sure Chief is preventing this due to code.

 

[John_B]

1 hour ago, ACADuser said:

Your walk line is at 2'-5".....

 

On this drawing it is, however, my interpretation of the code is 12" from the inner radius is where the walk-line should be measured,  not what is shown here at 2''-5"...

[Joe_Carrick]

That stair wold only be compliant if the inside radius was increased to about 4-1/2 feet.  The line shown by chief with the arrow isn't the "Walk Line" as required be code.

 

The other option would be to decrease the number of treads so that the minimum tread width at the walk line (12" from inside) would be 10" minimum.

[ACADuser]

Like this:

[Hammer7]

Make sure your in the right code section for spiral stairs if indeed that is what they are going for.  Spiral stairs have a separate section.

[para-CAD]

At the 12" walkline the tread should be 10" or greater.  It's only 8 ¼".

You're right to suspect these stairs.