Not sure how to describe this but…
model a box - add two side boxes to it and start to p/p up to a house where the two side boxes has different hights and roofshapes eventually… first p/p one height and then using ctrl+p/p to add next height level. The two side boxes leaves line traces on the main box -when deleting these the whole side disappears. How can I do this differently - is it a must to have the two side boxes in separate groups?!
Hi Susanne,
The vertical lines you highlight would be expected because the edges surround the face are broken by the vertical edges in the corners below. If when erasing those highlighted edges the faces disappear, that would imply the faces aren’t in the same plane. If the should be in the same plane you need to go back to your original geometry and check for alignment.
Did you draw this geometry in SketchUp or is it imported CAD linework?
Why do you have reversed faces in the lower section? How did you create that.
If you want to send me your .skp file I’ll take a look.
So many good questions Dave 
All drawn in SU ( I have imported .dwg but these are used as references)
Well really do not know why so many surfaces as become reversed? Honestly I thought it had to do with the style in use…
While waiting for input on this I have gone ahead and created a new rectangle on top and started to p/p that one....
But I still would want to know for future work - because it is the "house" and I would want all that in the same group. Now I am about to have two groups for the "Huset" and that is not what I really want...
I really need to get more efficient in this.... :-) :-)
I can sure send you the file... through email?
Email is fine if you’d like.
The exposed back faces can occur for a few different reasons. Depends on how you drew and extruded things.
I am facing same problem when creating the roof with the surface going outside the wall on the roof - no idea what this is called in English.
I do this with offset and deleting the inner frame - resulting in that the wall below gets screwed (see the garage) as I am using ctrl+p/p only a few cm this gap is hardly visible so I have just ignored it - but now I realize I need a better way of handling this…
This is aclue there’s something wrong with the geometry you started with.
For anyone else who comes along, the first issue has to do with the faces on either side of the vertical edge not being in the same plane. Drawing off axis makes it easy for that to happen. Rotating the model axes to align with the geometry can help.
In the case of faces disappearing after offsetting the top and deleting the inner edges, those edges are still required by the faces below. The fix is to extrude the offset face upward for the fascia border and then erase the top.
Even faster, nothing to erase.
Click in sequence on the scenes tabs of this SU file for ideas.
What Jean shows you is the other way I described to you when we were talking. It works well if you know the outer dimensions to start with.
Thank you Jean! Clever way However I build my houses from buttom up - so hard to get the bottom face and pull it down - but I guess I could do it with some moves maybe… Anyhow - thank you.
If you orbit your model, you can see it and model it from any orientation, including from the bottom.
Click in sequence on the scenes tabs of this SU file for ideas.
Roof with soffits.skp (33.3 KB)
This is a file I made a while ago for someone who had the same problems as you seem to have. Observe the use of Scenes that allows me to memorize the orbit, zoom and pan of my model. You can do the same using, for example a scene for a bottom view and another scene for a top view. Then, instead of orbiting, zooming and panning to get the required view, you simply click on the adequate scene tab. Remember that you can rename the scenes with names like “Top” or “Bottom” that are more explicit than “Scene 1” or “Scene 2”.