The most common size bag for earthbag (sand bag) building measures about 18”x30” measured when empty. This is often called a 50 pound bag, since these bags are used to store 50 lb. of grain and feed. When filled, this size creates walls about 15”-16” wide. This is a good size for earthbag building because they create stable walls with sufficient mass, and yet they’re not too heavy to handle. Even though earthbags are typically filled on the wall to reduce labor, there’s still a fair amount of sliding and aligning involved. Using bags larger than 18”x30” will require a lot more effort to construct your home. Even a small difference in size adds up. For example, I decided not to use some bags that measured about 19”x30” because I realized these bags would be more difficult to work with but not provide any appreciable added value.
There’s a larger size called 100 lb. bags that measure about 22”x36” measured when empty. Using larger bags will greatly slow construction, although they are very useful for specialized applications such as basement walls, rootcellars and earth sheltering. Larger bags are also more expensive and take extra fill material – more material than necessary for typical above-grade walls. Each additional cubic foot of fill material has to be shoveled, moved, put in bags and tamped. The larger size will work, but they’re much more difficult to build with since they’re much heavier. Plus, they take up additional space.