Wow, thanks for the very quick reply. Will try the instancing trick and see how render times compare.
I'm still trying to learn this tool, but have a hard time wrapping my head around it. The constraints of axis x,y,z does not work well with my intuative mindset after using the floor generator plugin from cg-source
My model faces are not perfectly aligned to the world axis, so just getting the first sloping roof to work has taken me more than an hour of trial and error. I tried setting it up as in your roof "eyebrow" file here: http://forum.itoosoft.com/index.php?topic=3271.msg12735#msg12735
It didn't really like my spline it seems. So now I've "brute forced" it with the tiles transform settings and adding a slope to my 2S spline drawn in top view.
Shouldn't I just be able to select the sides of the roof polygon, convert selection to splines, make this as my included clipping area, and use the sloping roof as surface object? Here I find it really hard to grasp how to get the object to align correctly to the surface (facade 3.jpg). Could you point me to a tutorial that explains this scenario better?
On a second note, the end clipping. Is this just fixed with a bottom/side object the same size as the main object? (facade 2.jpg) - so it won't mess the tiling pattern.
I will read Bertrands tutorial. Thank you very much for that. Might be the way to go for now.
Thanks again for great service.