This is another major announcement courtesy of Structure1.com. Instead of building buttresses, which tend to be time consuming and difficult to design correctly for earthquake zones, they recommend using the same specifications we reported earlier for reinforced earthbag walls in seismic regions. The comments below are from the latest email exchange with Structure1.com.
Refer to: ASTM E2392, Standard Guide for Design of Earthen Wall Building system. Please note that this empirical standard is applicable only when engineering design is not available.
Portions of the International Building Code, IBC, and ACI 530. Please note that chapter 5 of ACI allows unreinforced adobe only in Seismic Design Category A. So, it [unreinforced earthen construction] is not allowed in Seismic Design Category B, C, D, E and F. That is to say it is practically not allowed in more than 95% of the world.
If this is the case, reinforcing bars are always required. So, while buttresses add strength to earthbag construction, they are not required as long as we use reinforced steel bars. Buttresses can be eliminated to save money. The project will be more economical and comply with the building code with reinforcing steel bars only.
Once again, we owe a great deal of thanks to Structure1.com for their efforts to move earthbag building to the next level. Note: No one has received any money for any of this work! This is all pro bono work intended to help those most in need.