Hanging doors and windows in a load-bearing, Nebraska-style straw bale building can be a challenge. There’s just no way I that know to keep a two-foot wide straw bale wall from settling and no two bales are going to settle the same amount. To avoid jammed doors or cracked windows caused by shifting bucks, we built bucks with frames that extended from stem wall to bond beam.
Our bucks were built to do double duty. They were constructed to provide a secure and square opening for windows and doors as well as ensuring a strong mechanical connection between the stem wall and the bond beam, serving to tie our wall together. In this way, not only were our windows well secured, but our entire structure was strengthened.
We adapted this building strategy after looking at the work of a few straw bale builders here in Arizona and New Mexico and reading about the work of others.
Connecting to the Stem Wall
During construction of our stem walls, we identified and marked the location of our three and four foot windows on the stem wall. We inserted J-bolts in the core of the blocks when we filled them with concrete. These J-bolts provide the secure stem wall end of the mechanical connection to the roof via the bond beam. For the two by two bathroom windows, we didn’t feel we needed the full support of a stem wall to bond beam buck. So we used a floating buck for the small windows.
J-bolts were also installed adjacent to the door openings to secure the door bucks. On both door and window, we installed a 2 x 6 plate on the J-bolts and fastened the bucks to the plates with Simpson steel hurricane straps. We had not done this in building the small straw bale Annex and found that we needed the “wiggle room” for slight warp in lumber, unnoticed shifting of the J-bolts when coring, and just plain measuring a bit off. Fastening to a larger surface, such as the 2 x6, is much more forgiving.
Building the Bucks
The bucks are actually pretty straightforward. A box made of 3/4” inch plywood with 2 x 4 dimension lumber reinforcing across top and bottom with wall height 2 x 4s on both sides. Size your boxes by the actual size of the insert, whether door or window. Leave 1/4" per side wiggle room on the windows and more for the doors. I usually leave at least 1/2” per side.
Shimming a door for plumb is easier if you leave some room. You do NOT want the door opening too small and, unless you are very careful, door bucks tend to become a bit trapezoidal when packing bales on both sides. You may need to compensate for this, especially if it’s your first stab at straw bale building.
We determined the desired height of the window openings and mounted the sidepieces accordingly. For ease of construction, we positioned the box approximately 32” above the stem wall. Our bales are 15” high and two courses of bales would nicely fit under the windows with a minimum of hand filling. Inevitably a straw bale builder will have hand filling (stuffing loose straw into openings) to do in order to avoid gaps.
The trick is to do as little of this as possible as plastering over a solid bale is much easier than over a hand packed spot.
Before The Bales
After the plates were tightened to the J-bolts, we mounted the bucks. The most important considerations here are leveling the box, side to side and front to back, and plumbing the walls. Remember to establish a plane with the bucks to help establish a straight wall.
Reinforce the square of your bucks with diagonal temporary braces and further brace the bucks with a brace to a stake in the ground, especially if you have some wind as we do here.
Measurements and Flexibility
Our walls were intended to be about 9 feet high above the stem wall. So the sides of our bucks were built using 10’ 2 x 4s. When our walls were stacked and we were ready for bond beams, we simply cut off the excess with a saws-all.
The cuts were made up to 3” below the top of the bale wall to permit settling. The firmer your bales are, the smaller will be the amount of settling and the smaller the distance from buck to bond beam. Connections were made from the buck to the stem wall using steel strapping. After we installed the bond beams and the roof, we sat back and watched our walls settle for about two weeks. As the settling took place, the steel strapping, which was in place to keep the roof from flying off, would buckle at each connection. Taking out the screws on the bottom of the strap, tapping the strap straight and screwing in at a slight downward angle ever three or four days kept tension on the bond beams. By the end of the second week, the bond beams were touching the buck tops and we did a final fastening, using both screws and strapping nails.
I tend to use "about" and "approximately" a lot when talking about straw bale building. That is because no two bales are the same size, ever. To be successful in straw bale construction, we had to relax, be flexible, and learn a whole different definition of "custom building."
Before you start the process of mounting the bucks, building the walls, placing bond beams and roof, be sure you have all your material on the ground. The building will go up quickly if you do. Avoid last minute ordering of building material.
With help from our neighbors, Dan and Anneke, we were able to raise our walls and weather in the house and the porch in about a week. Pick a week with no rain in the forecast and enjoy the creation of your straw bale home. If you wish more information or a list of books we consulted, feel free to contact me.