I did a good bit of television work last year at the Norwegian folk
museum in Oslo and at the Maihaugen open-air museum in Lillehammer, both
of which can help you in the sod roof department. Basically, you need
heavy framing, birch bark, and sod on top. A fine book to help you, is
"the Craft of Log Building" by Herman Phelps, published by Lee Valley
tools of Canada. Excellent on how to frame for sod roofs. Will dig up
numbers for Norway somehow.
Good luck.
Roy