Stair surface to closed Brep

Hi everyone,

I’m having trouble turning my stair surface loft into a closed brep for further modelling.

I’m using curves distributed along a line to create lofts which I then join into an open Brep for the stairs.
However when I try to extrude and cap this to create a solid Brep, I end up with an invalid Brep and a lot of naked Brep Edges.

I’m not sure how to proceed at this moment. It’s important that the geometry remains a Brep and not a mesh, so I feel a bit limited in my toolbox to “weld” this problem.

For the final step I would like to use the support arch to trim the stairs and create a solid between the two. I was planning to use a solid intersection of the extrusions, but I can’t seem to be able to make my surface into a solid.

Help in this matter would be very much appreciated! (34.6 KB)


The naked edges appear to come from the extrusion of the vertical faces of the stairs.
I extruded all horizontal surfaces then Solid Union everything. (24.8 KB)

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Wow, that makes total sense, thank you so much Teddy!

Dear @magicteddy,

just one follow up,

for some reason the solid intersection gives me an empty result.
I gave some distance to the sharp end of the platform, which was my intention already, but still no results.

Do you have any ideas that explain the same script working on your pc, but not on mine?
This seems quite strange to me.

Thank you for your help! (26.8 KB) (24.8 KB)

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Rhino file tolerances, maybe ? Hit F5 in Grasshopper after changing those.
Both files return a closed brep on my PC.


If it still fails, the trick would be to extend your cutting surface, by building a larger sweep2. Tangent faces are always problematic with boolean operations.

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That last step is a doozy! Long drop.

upping the tolerance to 0.01 did the trick!

Don’t know if I’d ever be able to figure that one out on my own.
You’re like a Deus ex Machina Teddy, thank you so much.

I hear what your saying on tangent faces, will remember for future reference!

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