The importance of laying the bales in running bond, the pattern seen in brick walls, cannot be overstated. Indeed the very strength of the wall system is dependent, to some extent, on the inclusion of a running bond pattern. Consider how strong the walls of your Lego® castle would be if the running bond pattern was not used. “Not very strong at all” is likely the thought running through your mind as you consider this visual.

There are, however, situations where running bond is not a viable option and the wall must be stacked one bale directly on top of the other. A perfect example of this situation is when two or more windows are placed close enough to each other that there is only enough room for a column of bales in between them. Stacking seven or eight bales on top of each other is not very strong, especially if they are not full length bales. In a situation such as this, you must anchor the bales to the frame to increase their stability. Additional blocking which I call ‘squash blocking’, is typically required within the frame to make this possible. Install the blocking every three bales courses or so and nail them tightly to the frame with toe nails so that the block is squashed down onto the top of the bale.

Octagonal CornersAnother place where a continued running bond can be interrupted is when you need to switch from baling on the flat (strings on top and bottom), to baling on edge (strings facing the inside and outside).  Although this is a rare situation, it is sometimes required if a section of wall needs to be thinner than the section next to it. Rather than running the bales through a band saw or ripping them with a chainsaw, they can be laid on edge. The problem with this, of course, is that the bales on edge (18″ tall) are no longer the same size as the bales on the flat (14″ tall) so the running bond cannot continue. Again, the bales at the transition of these two techniques need to be anchored to the frame with additional detailing. I typically build a bale stop of 2×4 studs and plywood against which the transition is made. This is also a suitable transition for octagonal buildings and it ensures that the corners are strong and the baled sections are tight. During the meshing stage, the corners created by the two bale stops as shown in the photo are stuffed tightly with loose straw to complete the detail.

Running bond construction is not possible if the bales are interrupted by things such as windows that extend from floor to ceiling, doors, bookcases, etc. In these areas, it may be possible to rely on the strength of the mesh to anchor the bales to the frame; however, if the wall feels weak, it probably is and additional anchoring will be necessary. The bales can be anchored to the frame in a number of ways including with twine, strapping, mesh, or additional framing. I have found the simplest method is to use strapping provided through a company called Cordstrap®. As shown in the picture, it is a series of woven polyester threads incased in polymer webbing that is attached to the frame and then tightened with a special ratcheting tool that pulls the bales tightly to the frame with little physical effort.

Tight bales are essential for a quality plastering job so take the time to make sure you have the best substrate possible whether it be through the inclusion of running bond stacking or specific details designed to strengthen the walls in its absence.

Tomorrow we will investigate special considerations for High Rain Environments.

Happy Baling!

Andrew Morrison