Hello everyone, this is my first post here, love to use SH3D.

There's one thing I'd like to do, please forgive me if it's already been asked I didn't find what I'm looking for.

My house is an old farmhouse on two levels.

To draw each level I imported the technical drawings to use as a guide. But they don't match exactly, so now I have some discordance on walls between the two levels.

The building is so old that walls aren't straight, the second floor has been added in a second time by the old owners and the rooms are not specular to the ones on the ground level.
What I wanted to do is to draw the second level using the ground (first level) as a guide but I don't know how. Something like seeing walls of the first level but drawing on the second.

Is this possible?
Many thanks in advance!