Hi DesuDeus, is it possible for you to easily select all the roof plane pieces and then separate them out so you have a whole bunch of surfaces like you show in your example?

If so then you could do a batch convert of something like that by: Select naked edges (http://moi3d.com/forum/index.php?webtag=MOI&msg=4869.5), followed by Construct > Planar.

You may want to do something more like ctrl+c copy to copy the naked edges as curves, then delete the triangle surfaces, then paste the curves in, then run planar so that it will be easier to get rid of the triangles.

Let me know if that sequence does not work for you.

- Michael