Stair 22 and the different width of the landing

[Anonymous]

I'm sure it's something quite simple, but how does one change the width of a Landing in an Archicad 22 U-shaped stair?
I have a U-shaped stair that needs to have Flights 900 mm wide and a Landing in the middle that should be 1200 mm. Is there any obvious way of doing it that I'm missing?

[Laszlo Nagy]

I tried this by placing a U-shaped Stair and I tried modifying the Landing width by selecting the Boundary and adjusting it.
The curious thing for me is that if the space between the two Flight is below a certain amount, it will not allow me to do it. For example, it did not work with 200, 300, or 400 mm between the Flights, but did work when it was 900 mm, as can be seen on the screenshot. Also, in case it did allow it, it did not let me closer than 50 mm to the node on the Baseline that separates the Flight from the Landing. At the moment I could not figure out what is imposing these limitations, maybe some Landing or Connection setting, but I don't know yet.

[Anonymous]

Thanks for your reply, Laszlo,

At the end I got around it by modelling the stair with a reference line on the "inner" side and then it had no problem with stretching out the outer edge of the landing.

But it's a little strange and a little unintuitive that it doesn't let us do it the other way. Usually one starts to model a stair (place the reference line) from the "outside" since that's where the boundary/bearing construction usually is.

It would be good to know if there is any setting that is limiting the geometry of the landing just like you said.

[Laszlo Nagy]

Some info from GSHQ:
It is generally advisable to always place the Stair Baseline on the outside boundary of the Stair, and not the inside. That will probably save you some of these errors.
Before you start drawing the Stair Baseline you already know where its geometry will be so it is relatively easy to decide where to start drawing that Baseline.

[Anonymous]

I was just frustrated with this same problem on a project which we are designing with AC21. Besides drawing the stair using the "inner boundary" method, I found a solution which seemed to work, but it had some quirks. I think this would work only on simple monolithic stairs (like mine), but haven't done extensive testing.

So I found out the same weird thing Laszlo did, namely that trying to extend the landing boundary wouldn't let the landing be stretched all the way to the edge. The distance it let me stretch didn't really make sense, could not figure out where it came from.

The trick I found out is that instead of extending the "back" boundary, I could extend the "side boundary". This boundary seems to be able to connect to the adjacent side so that the final stair seemed to look all right at least on plan view and quick 3d check. I mentioned this has some quirks and might not work on more complex stairs because the actual boundary line still includes a zero width "extra" boundary I could not get rid of. (Seen in picture 4) The extra boundary however does not show up in normal (unselected) plan view for me.

I'll attach some images to describe this better. The F-marked parts are drawn as flight boundaries, and L-marked parts are drawn as landing boundaries. I was aiming for a stair that has 1200mm width and 1350mm wide landing.