[Cob] trench rocks with or without sand

[Jaanus Viese]

   Hello Cobbers!
   I build small cob-strawbale cottage about 12x12 foot. The ground
   beneath cottage is very sandy - 10 inch soil and then only fine sand.
   The winter is very cold in our climate (0 until -25 by celsius, like
   middle Canada or
   so). I built roof structure and digged trench. Next I will fill trench
   with 1-5 inch diameter small stones (like "big" rubble). The cottage
   floor will be made from
   sand-clay. Foundation will be stones with lime-cement
   mortar.
   1. My question is about trench filling. Do I have to fill
   gaps between trench stones (between rubble rocks) with sand/gravel?
   When I do not fill gaps, then the sand/gravel from floor base might
   flow into the gaps beneath
   foundation. As a result the floor will be damaged.
   The second option is to cover the rubble trench (stones)
   vertically with some kind of landscape plastic and protect that way
   the gaps between stones.
   2. I have heard that some builders fill the trench with big stones
   (5-12 inch stone) and then fill the gaps
   with sand or gravel. Does anybody has experience with such kind of
   sand and stone filled trench? What are probable dangers with or
   without sand filling (water stands and frost etc)?
   Best
   regards,
   Jaanus from Estonia
   Jaanus
   Viese
   www.juured.ee
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References

   1. http://www.elu24.ee/?id=3717
   2. http://www.elu24.ee/