So I have been quit busy doing the challenge. But it is a lot of work, there are a few small things that I want do complete before continuing to the next course seminar like:
Placing the roof and moving the wire gutters down a bit.
And I had trouble as a lot pieces where just off buy 0.00023445. And redoing half the building was braking my hart so…
I made a python script to round the position of the selected object to a tenth of a unit and thus making the whole construction flush once more …
I am posting it here in the hope someone else might find it help-full 
import bpy
import mathutils
print("Start run ...")
vec = mathutils.Vector((0.0, 0.0, 0.0))
for obj in bpy.context.selected_objects:
# for coord in obj.matrix_world.to_translation():
# print(coord.x)
#print(round(obj.matrix_world.to_translation().x,1))
print(obj.location.x)
vec.x = round(obj.location.x,1)
vec.y = round(obj.location.y,1)
vec.z = round(obj.location.z,1)
print(vec)
obj.location = vec
print("After Operation:")
print(obj.location.x)
