[Cob] Plastering over plywood?

[rodger at inbox.com]

Hi folks,

I am moving into an old homestead log cabin with a loft bed.  The logs are obviously beautiful, but the gabled ends and the ceiling are covered in just old plywood that looks awful.  I'd like to cover it with something other than just paint.

I've plastered with clay plasters a lot, but I've never done a ceiling on a 45 degree angle, and over plywood.  

Some data... The roof is 2x6 rafters that are 11 feet long from wall to ridge.  Plywood is 1/4 inch, screwed on well.  There's a wood stove for heating in winter(an eastern Canadian winter...2 foot snow load in minus 25 celsius at worst), so there'd be some expansion and contraction.

I'd LIKE to put an earthen/clay plaster over the plywood.

What do you think?  
Am I crazy?  
Would it hold?  
Would it just crack to all hell in a year or two?
Fall to the ground?

Do I have to bridge the seams with something special?  I was thinking... lots of fiber, and maybe burlap over seams.
What kind of adhesion coat should I use to get the plaster to really hold?  I was thinking a mix of sand, clay and wood glue.

Your vast wealth of knowledge and experience is being invoked!  I appreciate any suggestions!

Rodger in Wakefield, Quebec, Canada

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