topic Re: Stair Tool fails to generate U-shaped winder stair with a narrow (10cm) inner gap (Archicad 29) in Modeling

Stair Tool fails to generate U-shaped winder stair with a narrow (10cm) inner gap (Archicad 29)

MimarEmirSimsek — Tue, 05 May 2026 15:20:57 GMT

Hello everyone,

I am transitioning from AutoCAD to Archicad and I'm currently using Archicad 29. I am trying to model a specific U-shaped stair with winders based on an existing 2D AutoCAD drawing, but the Stair Tool keeps failing. When I try to draw it, the stair either completely disappears (aborts generation) or creates a severely distorted geometry.

Here are my exact stair parameters:

Total height: 288 cm
Risers: 18 (16 cm height)
Going: 27 cm
Flight width: 100 cm
The central gap (stairwell) is only 10 cm wide

I disabled ALL the restrictions in the "Rules & Standards" tab (Min/Max Riser, Going, 2R+G, Minimum Winder Tread Width, etc.).

I tried using the Magic Wand (Spacebar) on a pre-drawn 2D outer boundary, and also tried it on a center baseline.

I experimented with turning types, especially switching to "Winder with Equal Angles".

Since I am still learning, any step-by-step guidance would be fantastic

Operating system used: Windows

Re: Stair Tool fails to generate U-shaped winder stair with a narrow (10cm) inner gap (Archicad 29)

Patrick M — Tue, 05 May 2026 14:25:09 GMT

In my experience, winder stairs have very strict code requirements that the stair tool fails to effectively meet. Because these code requirements vary from jurisdiction to jurisciction, and because the stair tool itself is guided by the limitations of its coding; I find it most effective to use it as a basic "close enough" level of modeling for most designs.
It works great as a schematic level design tool, or for projects which have a person who can dedicate the time to figure it out. But for a simple stair layout like you have here, I wouldn't even try. I could model it 10x over before I could get the stair tool to get even 50% accurate.
Use slabs for treads, overlapping to represent nosing. Model the stringers/body with either a series of roofs or a morph, subtract with upward extrusion. The morph has the advantage of being able to sculpt the bottom face to flow with the stair slope.

Re: Stair Tool fails to generate U-shaped winder stair with a narrow (10cm) inner gap (Archicad 29)

Patrick M — Tue, 05 May 2026 21:50:05 GMT

here's a 20 min video on stair tool vs slabs/morphs... Its a bit of a tedious watch; sorry about that... was totally on the fly, but hopefully it helps you get what you need.
...

wont let me embed in the post, but try this: https://youtu.be/s9ltqVGozDQ