Curved stair form

Hi! I am trying to create a monolithic curved stair from around a irregular plan shape and need help on how to achieve it.
We want it to resemble an elegant smooth sculptural form (probably plaster) similar to that of Harry Seidlers.
The problem is that it is not a properly round shape, and it is created from a series of ellipses, as you can see from the plan:

I have been trying to use curviloft plugin and have not had much luck.
Ideally i would love if there was a plugin or something similar that can create a smooth spline in 3d, so i can follow the form of the stair down (cant use a helix as it does not follow a circle) and use that as a path to extrude via ‘follow me’. Does anyone know of one?
Or any other suggestions?
Is there anyone who can help?? We have a deadline for tomorrow and am running out of time :frowning:

RCM curved Stair.skp (336.9 KB)


Maybe it’s the language barrier but I, for one, can’t actually understand what do you want to do.
Do you want the railings ? Do you want to create a wall under the stairs ?
A simple example would help.

Sorry, Let me explain better- I want to create a ribbon like railing/wall to both sides of the stair. Similar to this:

But smoother so it dosent jump and stagger at the landings. It’s really hard!

I would manually move the top edges to create a smooth curve along.
But the height of the sides will not be even, some places will be higher some places lower. You can just smooth the transition between the sloped and the straight portions.
Here’s how I thought it will work. Just a few edges moved and the slopes scaled up or down as needed.

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You could use a Bezier curve as your path.
A quick version here, I haven’t bothered to make it fit perfectly, but you can add control points as necessary to shape the curve.

Thanks! That is what i want to do, but i struggle!
How did you create the thickness to the walls? I have been making 1 surface, then use Joint push pull to thicken it- but it isn’t very smooth as any irregularities become super obvious

Thanks- I did end up trying this spline, but i cant make it follow the stair shape exactly so have to tweak the plan of the stair treads to accommodate the spline which isn’t ideal!

Another option then would be to trace the shape on the flat using arcs, then use CurviShear, from Fredo tools to lift it.

You can see how I changed the older normal profiles by looking at the pictures I uploaded.
I used Joint Push Pull, but because I have already made a smooth transition between the straight and the sloped portions it came out pretty nice.
You can still see a bit of a problem in the inner portion, but manageable. You can individually move those endpoints to have a better look.