Nebraska style (load bearing ) strawbale walls require stacking and pinning.
Bale stacking begins with one fundamental rule: begin with full sized bales at wall corners and door and window openings, and stack toward the center of the wall.Bales are usually stacked in a running bond, meaning that the second layer, or course, of bales is staggered atop the first so that the middle of each bale in the next higher layer is located over the seam between two bales on the lower layer. Stacking using a running bond produces a wall that is stronger and more stable.
The overlapping of bales means that at corners, windows, and door openings, some bales will have to be re-tied into shorter lengths. Bales may be shortened using either of two basic methods. In the first method, bales are shortened by by piercing the bale through with a bale needle (or similar), to which is threaded new twine, at the desired new bale length. The bale is re-tied, the original ties are cut, and the new, shorter bale is separated from the original length of bale. This method retains the tension on the straw. The other method of re-sizing bales is the cut the ties, separate the bale, insert the bale into a makeshift bale press, apply pressure to the down-sized bales, and re-tie the strings or wire. Both methods have their enthusiasts.
All bales are pinned together to increase the walls' resistance to wind and seismic induced loads. The first layer of bales is impaled upon short lengths of re-rod which have been embedded in the wall foundation or slab. Thus the first layer of bales is thus held in place and prevented from moving from side to side on the foundation or slab. Subsequent courses of bales are pinned to the courses below by driving bamboo, wood, or steel re-rod pins from above. These vertically oriented pins are located so as not to harm the bale tie wire or twine, and are also set back from the ends of the bales so that the pins enter each bale in the lower courses away from the ends of the bales, and so that the pins firmly tie together all bales vertically. Particular attention must be paid to all wall corners to ensure that the bales of the intersecting walls are well pinned to each other. The need to pin bales means that pinning techniques must be chosen, and pinning materials must be procured (and cut and/or sharpened) before a wall raising can occur.
Steel pins, cut from long lengths of re-rod, are easy to use and are a common choice. Alternatively, lengths of bamboo or wood dowel can be used, though pins made of these materials usually must be sharpened so the pin can pierce the bale. The choice of pinning method and material will certainly need to be specified to local building officials.
Wall stability mandates that openings in strawbale walls be located not less than four feet from a wall, and that the bales in two intersecting walls overlap up the corner. Maximum wall height should not exceed 5.5 times the width of the bales used, and maximum unsupported (unsteadied) wall length should not exceed 15.5 times the width of the bales.