Well, I guess the lines somehow really weren´t completely together, but in section and floorplan they looked OK. Is there maybe a way to set 3D view a bit less rpecise (meaning that the lines that are very close would be ignored? So that a 3D line view would be a bit more simplified?
Where you see the line between the two Walls, the End Points of the two Walls are probably not exactly on top of each other, thus their vertical surfaces are not co-planar and you see the line.
Just zoom in very very close (as much as you can) to each common node of the two Walls and move either one as necessary to make sure they are completely on top of each other.
This of course brings up the matter of modeling accuracy. If you have to move of the Wall Nodes, then it may no longer be orthogonal. So you want to keep the Wall that is truly orthogonal, and move the Node of the Wall that is infinitesimally not orthogonal.
However, in Section, the situation is much simpler, the top of the lower Wall is exactly at the same height as the bottom of the upper Wall, so they touch in Section and so their Cut Fills merge and there is no line. These are two separate mechanisms.
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