Hi Paul, just found this forum & richsoil - yeah!!!  (looooong -time DIY/self-sufficiency afficionado 

  I'm in hog heaven purusing all this stuff!  (took years of leave for political activism - Bucky was right - it is a dead end - back to my heart's desire 
 
    Just a quick insert re: wofati (yes, I too ran across Oehler years ago 

 at richsoil -  //...'if polyethelene could be replaced with....racking my brain...'//.  See pg 14 of 
Planting Green Roofs and Living Walls, N Dunnet et al - "Diagram of traditional Scandanavian turf roof with sections of 
birch bark forming a waterproof layer." 
 (Now to go wallow in more of the Rich Soil here.... 
