It’s very easy to install electrical boxes in earthbag walls. The process involves two basic steps:
1. Anchors: Add anchors in the wall where electrical boxes will go. Do this as the wall is being built. You could use 2x4s placed between earthbags as anchors. Another way is by placing 3” diameter poles about 7” long between earthbags. You could also sharpen the poles and pound them in before the wall gets too hard. We use eucalyptus poles to deter termites. (Scraps left over from our roof poles and braces.) Be careful not to put them in too far. You want the front of the box to protrude about 1-1/4” beyond the earthbags to match the plaster.
2. Electrical boxes: After your earthbag walls are built, attach each electrical box to the anchor with two screws. This prevents boxes from rotating or jiggling loose over time.
Once the boxes are mounted, you can run electrical wire from box to box in the recess between earthbags. “UF” direct burial wire is one code-approved option (in some areas). You could use regular Romex wire if money is tight and there are no codes. The wires will get covered with about 3” of plaster. Some codes may require conduit, which is better if you can afford it. Conduit provides greater protection and enables you to add more lines in future.