I received an email today about a bale landscape wall. The wall will be about 4′ tall and 125′ long. The questions ranged from what type of foundation is best and what kind of waterproofing is needed to where to find bale needles. I have included my response below.
Sounds like a fun project! If you keep the wall at 3 bales high, you will end up with a four and a half foot wall, roughly. You will need to raise the bales off of the ground by at least 6″. The foundation you use depends on the soils you have. In most cases, you should be able to dig a trench deep enough to drop below the frost line and then fill it with compacted gravel. For the top 6″ before the top of the trench, and for 6″ above grade (12″ total) form a concrete bond beam. You will need to hold the bales off of the concrete with pressure treated sills which should be attached to the concrete with anchor bolts about 4′ on center. I suggest using 4×4’s and then nail 20 penny nails into those sills at 6″ on center on both sills (there will be one on each side of the foundation to support the bales as in the house details.) To protect the bales from rain, which is important as you suggest, use either a metal fabricated cap (specially made) over the top of the wall or a pond liner draped over the top and down the sides about one bale course under the plaster. The barley straw will be fine as long as it is dry and the bales are tight. You will want to wrap the wall in mesh so to strengthen it. Finally, we have bale needles for sale and twine can be purchased at your local farming supply store. You will want two needles so that one on each side of the wall can be used to sew the mesh together quickly. Good luck with the project.