[Cob] National Park Service earthbag construction

[Patrick Newberry]

Yes you are right, a single bag looping over a form would not work even if left till the end,  without stabilizing (i.e cement)  the mix. Other wise the multiple bags would be used to create keystone. The long bag over that is optional. 

Pat Newberry
www.gypsyfarm.com






  With nothing in the bags 
except sand and clay (at best) I don't believe a long bag looping up over 
an opening can work, even if the form is left in till the end. When there's 
no cement the arches have to made of many bags rammed into wedge shapes 
with the top one acting as a keystone, THEN a long bag may be laid over the 
top to help lock them together (or openings can be corbelled in SOME 
situations). Cement could be used only in the arched bags but, because some 
of them continue on to become part of the general, wall I think all the 
earth used in those structures is stabilized with cement.

 >
>(this picture:  http://www.calearth.org/cvillage/DlxArch.htm )