Cutting and splitting problems

I am having a lot of trouble performing basic exercises in Rhino. For instance, look at image below and file.
I am quite unable to cut hole in wall. I draw rectangular curve on surface. I use wirecut tool. This does not work. I draw a box which is classified as closed extrusion and try boolean difference. This does not work.
I draw rectangular curve on surface at top right. When I use wirecut tool I get a sort of extrusion. Why is that?

I had hoped blue staircase might be used for a boolean split on red wall but does not work.
Under Units I have set absolute tolerance to 0.000001

Staircase is formed of a polysurface and extrusion joined together. Is that the source of the problem.

Can anyone tell me what is going on?

Building 14 03 21.3dm (1.3 MB)

you did not work precise enough. cleaning up such stuff should do the trick. i did not iterate through all of it but i guess taking a bit more care might be a good start.

Bildschirmfoto 2021-03-14 um 18.59.05

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Far too small - try to keep it no smaller than 0.0001

Your model is kind of a mess… The vertical wall is an open structure, I don’t know how you made it, but that is one cause of your problems. That is why trying to cut a hole in it didn’t work.

The blue stairs is a group of two objects, you can’t union them into one piece because there is a 1mm gap between them.

I suggest you start over with .001 tolerances - you do not need to model building walls with sub-micron tolerances - and you model your curves carefully and accurately and check before extruding them into surfaces/solids.

:joy:

that said in such cases cheating a bit in the other direction can help sometimes.

Well the original wall was an open polysurface which didn’t work very well
I recreated it as a closed extrusion
I ususally create walls for buildings by creating plan as closed curve and then extrude closed planar curve which I assume is same as extrudecrv
Do these two approaches constitute the best approach to making walls?
If I wanted to use staircase to boolean split would I have no option to recreate it from scratch. Or can I explode it

They’re fine if the input curves are good.

BooleanSplit splits one set of (closed) polysurfaces with a second set. The first set is split, the second set remains. But why do you want to use BooleanSplit in the first place? What is the end goal?

Maybe I want wall to stop on underside of staircase