Staircase - please help

[GG_rakurs]

I'm sorry for such a dramatic title but I have been unsuccessfully trying to create a staircase for the past 20-something working hours.

I need to create a staircase with the following conditions:

• Story height = 324 cm
• Riser height = 18 cm (18 total heights × 18 cm = 324 cm)
• Going depth = 28 cm
• Width = 91,5 cm
• Structure = 20 cm, concrete (probably 18 cm or even less would work, but that's for the associate engineer to calculate - I would need a functioning object that would not break apart if anything needs to be changed)
• Finish = 3 cm tread, 2 cm riser

I am out of ideas. I realize that a staircase in ArchiCAD cannot self-intersect on the floor plan. This one technically just barely doesn't.

I have tried separating it into two different staircases, manually connecting them and doing the symbols mostly manually. But I do need a functioning 3D for the sections.

Also, because of how formwork is done and because finish will show up in formwork plans if I don't SEO the stair with a finish-only copy of itself, the staircase MUST be functional in the sense that it won't break itself if I touch anything, and also I might need to make the structure thinner, from 20 cm to 18 or 16 cm slab thickness.

I've had quite a few attempts in drawing this staircase where it would just break and undo geometry if I do a slightest change, even changing the Element ID, and I'm not joking.

The problems probably arise from the fact that one turn has one rule for the winders, and the other turn has a different rule. It just won't play nicely no matter what I do.

Please help!

My ArchiCAD is striking a pose:

It does not offer solutions. As you can see, it has wrong ending with four winding stairs and I need only two. Most changes I make in the right direction don't allow me to continue changing, in the sense that the staircase becomes "locked-in" to certain settings and won't allow changes to those settings, which in turn makes me undo the change and try a different path and... hit some other issue which locks some other setting and...

Things I tried:

- Making the staircase from one piece. It seems that self-intersection rules do not allow it, but I'm not sure - technically the staircase does not self-intersect.

- Making a couple of continued staircases (as can be seen above) and the ending staircase doesn't want to play nicely. It just doesn't want to end like I need it to end.

- Making the upper part (staircase #2) a stair or even two stairs longer (and higher than necessary) so I would manually SEO it. Nope.

- Making variations of the above in a million ways.

I must be doing something wrong because this doesn't even seem to be too complex. Or am I wrong?

I've even tried to construct the staircase in Rhino but I don't know how to create the reinforced concrete part:

The OffsetSrf command breaks apart the polysurface that should be the upper surface from which the concrete part should measure the thickness. That's just my limited Rhino knowledge, unfortunately.

I'm at a loss, and the deadline is killing me. 😞

Operating system used: Windows W11H 24H2

[GG_rakurs]

It looks like I have succeeded.

1) I separated the staircase after the first full turn and before the second.

2) I made the second part one step longer / higher than it needs to be because the winding end wasn't working properly.

3) I used the slab(s) to cut off the parts going above needed elevation.

4) I duplicated all the stairs. The doubles were used as structure + finish, while the originals only have finish. They are put in separate layers, and then the stairs with structure and finish were used as SEO subtraction target, and the ones with only finish were used as operator. By doing that, I will have clean stair representation when using filter "core of load-bearing elements only" because the stairs are still not properly done in that regard within normal ArchiCAD workflow - finish stays on them. It's a well known bug that persists throughout many versions.

4) I disabled the walking line / description in the model view options and manually added them.

5) For description, I used autotexts where possible and manual entries where needed.

???

Profit.

(Loss of too many working hours but what is done is done.)

Basement:

This staircase (Basement to ground floor) is in one piece. It just works. However, disabling things in MVO means I had to manually draw the arrow and provide description.

Ground floor:

The selected part shows where the cut-off was made.

First floor:

Again, selected part shows where the cut-off is.

For floor plan display, I use only the stairs in the structure layer because the other ones with only finish show two lines for every riser.

[graava · Accepted solution]

I'm not sure if there's a way to model this staircase in just one piece but here's a possible solution with the staircase split in two.

Final result:

Hope it helps

[GG_rakurs]

Thank you, a great video. In the end, I got the result, but I will watch your video very carefully to see what I can do to improve. I already see that you've used a little bit different technique for the upper part, but the result looks correct too.

Thanks again for your time, much appreciated!