Hello, I did what Mike described.(I think...)



I set in preferences panel :
floor = 25 cm
height of new walls = 0,1 cm

then I made a stack of rooms.
export all of them in one unique OBJ format.
In a new project import the terrain as furniture. (and change the preferences to standard values)
Put the house at elevation corresponding to the height of terrain.

I would like to be able to make a bevel in order to avoid these stairs...but I don't know how...