The most recent issue of The Last Straw journal (#60) has my article about earthbag/stone foundations. The following information is just a short excerpt. You can buy the full length article from The Last Straw. The design outlined here can be used with load-bearing and non load-bearing straw bale walls, earthbag walls, cob, adobe, cordwood and other wide wall building systems. The drawing shown above has been modified to show earthbag walls instead of straw bale walls.
Polypropylene bags come in various sizes. Two common sizes are 18” and 24” wide bags. When 18” bags are stacked on top of 24” bags, there’s a ledge created that can be used to support stonework. (See drawing.)
When filled with gravel, 18” bags are about 15” wide. Filled 24” bags are about 20” wide. That leaves about 4”-5” for stonework. Consider double bagging the foundation (one bag inside another) for extra strength and durability. And, as always, protect the bags from sunlight.
Besides being extremely durable, using stone in a foundation just ‘looks right.’ A combination of stone, earthbags, and scoria as a fill material makes for a high-quality, durable, insulated foundation with many advantages.
You can purchase single issues, subscriptions and back issues from The Last Straw.