Deleting inner walls in building


I am trying to delete all interior partitions in this breps and end up with a final “shell” made only of the external parts of the brep faces.
As you can see, multiple surfaces are extruded and, therefore, interior walls are created.

I can’t seem to find and answer to this problem. Help will be much appreciated.


Hello and welcome to the forum,

In order to get the best help possible, please attach your geometry.

As a guess, probably a Region Union of all the initial contours, then Boundary Surfaces and Extrude.

Thank you magicteddy,

I’m afraid the region union option applied to the initial boundaries can’t work since every boundary has a different extrusion value.
I am considering a solution in line with deleting all intersecting faces but I can’t seem to make it work.
I am attaching the Rh/gh files as a sample.

Base.3dm (1.2 MB) (6.0 KB)

You could probably create a loop and create a boolean union with the closest extrusion one after another. But I don’t know how to do that so my second attempt was to create point groups which would hopefully result in sets that union… Needed two loops and the resulting Brep has no naked edges. There are some manifold edges, which is no surprise when extruding ‘boxes’ with varying height and touching corners. Despite the manifold edges, the mesh could be printed. (141.3 KB)


Well, I’ve been trying to do that for the past two hours and I’m still left with three breps that don’t join in Grasshopper (but do in Rhino) and a bunch of naked edges (and surprisingly no non-manifold edges), so I quit ! (11.8 KB)


Hmmm… I baked your open brep and at least some of your naked edges look a lot like non manifold edges.

@Alex35 what is the reason you want to eliminate the inner walls?

Yes, and the odd thing is that is I bake the extrusions and just continuously use BooleanUnion, while also doing Explode/Join when the result becomes open, it works and the end result is a closed Brep :man_facepalming:

Note : same thing happens on the final open brep of my file, baked, exploded and joined : becomes closed !

Base.3dm (3.2 MB)

Thanks a lot for your dedication, I will take a look into your answers and see if I can figure it out.

Removing the inner walls is needed in order to perform an energetic simulation.
If inner walls are present, results can differ quite a bit from reality.
Anyway, thank you for your interest and work Martin, I will review your answers and try figure it out.