I’m been saying for quite a while the easiest, fastest shape to build with earthbags is a roundhouse. Build one roundhouse and then add on later if you want to avoid debt. Adding a connecting space – two straight joining walls as shown above — is a simple solution for joining roundhouses. This simplifies roof construction since standard trusses can be used. Other options include reciprocal roofs, pole frame, etc. Using the connecting space as a greenhouse is ideal so you have at least some organic home-based food production nearly year-round.
How to add on in the future — put a window where you will need a door someday. Plan ahead and you could create more complex house designs with multiple roundhouses and possibly other shapes for unlimited design possibilities. Here’s my advice for adding on: Put a window where you’ll need a door someday. As you’re building the roundhouse, frame out the opening just like a door. Add some bags inside the frame to windowsill height and then build the window frame and window. At a later date it’s easy to remove the window, cut the plaster with an abrasive blade in a power saw, knock out the filler bags and install a door. Voila! In about one hour or so you’ll have a doorway to your new addition.