I built a 10'X12' 1-1/2 story shed frame w/9X9 beams and posts recycled from a mine.

The roofing is now almost completed. It is made up of 1"x6"x6' cedar fence boards. There is no roof sheathing. The pattern of layment of boards followed that described for boarded roofs by Hermann Phleps, in his book offered by Lee Valley Tools. For those not familiar, the boards are doubly layed and staggered, and courses are overlapped just like shingles, giving anywhere from 2 to 4 boards thickness. Short story- its a heavy roof (compared to metal) and I can set up, by shouldering into a principal rafter, very small amplitude (but detectable) low frequency damped oscillations in the entire frame, which is not yet planked. I don't know if this is usually the case with a heavy roof on an unplanked frame. My joinery is not perfect but its not too bad either.

Question: will the planking help stiffen the frame against this vibration? Is this simply because right now the structure is top heavy? Sobon mentions old barn planks that were as thick as 3" and that these could often take the place of knee braces: should I go with 2" dimensional fir planks or will 1" cedar board and batten stiffen the frame sufficiently?

Thanks in advance for any insight you can provide this long-winded, rank novice.
Sincerely,
David Lowry

Your structure will probably get considerably stiffer when you sheath the walls. Unless frames are "braced frames" similar to steel consturction they get most of their lateral stiffness from the sheathing. (most traditional style american frames are not the braced type.)

Sounds like a beautiful roof.