It's more easy with this crazzy free TopMod
Else you can in sketchup with Artisan
make a rectangular tubular forms then subdivide them
[flash=420,315:25wkk97y]http://www.youtube.com/v/bvqDlLYkPXU[/flash:25wkk97y]
See the videos under cuviloft for ideas. You can make the roof easily.
See the first overall video second example. Stitches single lines together thereby defining the plane.