Strengthen Your Walls

Written by Andrew Morrison

Strengthen Your WallsIf you look at the picture to the right, and you know about my style of construction, you might think that when I talk about ways to strengthen your walls that I am going to talk about mesh. Although I am a big proponent of using mesh on my straw bale walls, that is not the topic of this conversation. Instead, I want you to focus on the boxed soffit above the bales. That is where a huge amount of strength is built into this wall. The soffit does not always need to be that big in order to get the strength because it’s not the box itself that makes the wall strong. The key is in the location of that box, or more precisely, the elevation of the box.

By placing the bottom of the box LOWER than the height of the total amount of bales to be stack underneath it by 2″ to 4″, we make the space too small for the bale stack to comfortably fit. This means that the bales will have to be forced into position. This force provides a huge amount of compression on the walls and tightens things up tremendously. For those of you who have been to one of my workshops, you have experienced this firsthand and can attest to the increase in wall strength this procedure provides (and the sweat it requires!). There are several ways to get the bales to fit into this small space. None of them is what I would consider to be easy, but that is actually the point. If it were easy, the walls would not be very tight. Hopefully that doesn’t scare you away.

Strengthen Your WallsThe fact of the matter is that we can minimize the difficulty, but as is true with so many aspects of home construction, this process will take some sweat to do properly. The photo to the left was taken in the recent Australia hands-on workshop and many of the participants did not believe we would be able to get the last bale course to fit into the space provided. They thought it was too small for a full size course of bales to fit into. In the end, it did fit (after some persuasion) and the walls were incredibly tight as a result of the participant’s hard work. I’ve outlined the best approach to achieve this large amount of compression with relative “ease” for you below.

  • Lay two ratchet straps over the top of the second to last course of bales. It is best to lay these over a piece of 1/2″ plywood so that they will not bight into the bales when tightened. Make that plywood wide enough so that you can cut two handles into it that will stick out beyond the face of the bale wall when installed. The handles make the perfect spot for the straps to pass through. This gives you a way to get the plywood OUT after the wall is tight.
  • Place a small section of 2×6 on top of the second to last course of bales, on top of the plywood and in such a way that you can compress the entire bale with which you are working. By the way, we are working one bale at a time here…
  • Attach the ratchet straps firmly at the base of the wall. You may want to use large nails driven into the toe ups or, better yet, cut a piece of 1/2″ plywood that can be attached to the toe ups and has a cut out for the strap hooks to attach to. A 2′ x 2′ piece should be sufficient.
  • Install a scissor jack (or two if that works better to push the bale down evenly) between the 2×6 and the bale stop (box soffit). If you cannot line the jack up underneath a framing member within the box, be sure to span across the soffit with a piece of 2×4 so that you don’t attempt to tighten the wall against only the 1/2″ layer of plywood of the box soffit. In fact, you may choose to “permanently” attach a piece of 2×4 to the top of the jack for the purpose of the wall tightening wide enough to span from outer frame to outer frame of the soffit (roughly 18″).
  • Crank the jack down to compress the wall. As the wall tightens up, tighten up the straps to hold things in place. Go back and forth between using the jack to compress the walls and the straps to hold things in place. Don’t try to use the straps to pull the wall down as you are better off using the jack.
  • Be careful to watch that the wall doesn’t pop out of plane and fall over!
  • Once fully compressed and secured with the ratchet straps, remove the jack(s) and slide in the final bale for that area. It may take more muscle than you would expect, but that is okay…tighter is better!
  • Remove the tension from the straps and then pull the straps out of the wall.
  • Remove the top piece of plywood (this takes effort) and the strap anchor plywood pieces and move to the next bale.

Sound like a lot of work? Well, it kind of is. The good news is that every other aspect off the construction that you do moving forward from this point on will be easier as a result of the wall tightness. Stuffing, shaping, meshing, sewing, installing electrical and cabinets, plastering, and absolutely everything else will be easier. It’s like the old adage “spend a dime to save a dollar.” For me, the extra work is more than worth it in the end and the quality of the overall job you will get as a result of this step is measurably better than working with soft or loose walls. If you have other ways of accomplishing the same level of wall compression (or better), I’d love to hear about them in the comments section below.

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16 Responses

  1. Hi Andrew…….I have been following your website for some time now as I have been in the process of building my own bale cabin/house. The superstructure is made of logs with a more or less conventional roof (metal) already in place.
    As this is all new to me I seem to need to be a few steps ahead of myself when it comes to planning my next steps.
    Your suggestion of compressing the bales is a very good one and while pondering it myself I came up with my own method which I have experimented with.
    Much the same as yours but instead of the scissor jacks I used two expanding hydraulic jacks that were used in automobiles which I got from the auto junk yard. The slot normally used for attaching the rod for twisting the raising mechanism neatly fits a standard 1/2″ spade bit. Ones needs simply put one on each side of the bale in question below your box beam and raise it in seconds with a cordless screwdriver which will provide a surprising amount of force.
    thought it could be of some use to you…………cheers…..bruce doyle

  2. Andrew;

    I used plywood placed NEXT to the space where the bale is to be placed. I also used a small hydraulic car jack. I was able to compress the bales a good four inches using this method. The bales did not take much persuasion to put into place, and it was amazing to watch them compress when the jack was released. By placing the jack next to the space, I did not have to fight pulling out the piece of plywood since it was not under the bale. This worked great and definitely tightened up the walls!

    Rick Callahan

  3. hello Andrew,

    Could it be possible in some way to lift up the upper construction of the roof a few inches, and lower it down on the bales after the last course of bales is put in place? This means one has to made some adaptions to the consrtuction; that it will stay in place as long its lifted. This could save a lot of work and time?

    Keep up the good work!

  4. Hi Ger. Thanks for the idea. That would be way too much in the end. The roof assembly is SUPER heavy and would take far too much to lift and hold in place. Also, it needs to be held down to the wall framing per code, and once the bales are in place, there would not be access to attach the required hold downs and attachments. Thanks for the input though. Thinking outside the box is what makes great ideas!

  5. Hi Rick. This is good to hear. I have had trouble with the bales NEXT to the location in question not providing enough compression in the location I am trying to fill. I’m glad to hear it worked for you. Any other tips as to how you made it work?

  6. Hi, I have a question with regards to the compressing. Would this be possible on a load-bearing (Nebraska style) strawbale house? I’m not sure how construction works for that but it would seem that the roof structure would go on after the bale walls since they provide the structural support, thus there wouldn’t be anything to Jack against and compress.

  7. How about stacking the bale, placing the bottom plywood peace of the box on top of the bale, pushing it all down with jacks, then building the rest of the box. Forgive me if this is totally ignorant. I am just learning.

  8. Hi Jonathan. Load bearing construction has a different approach. That said, it is absolutely vital (even more so in load bearing construction) to get the compression tight. In load bearing, we use straps to draw the box beam (the piece added above the bales that the roof will sit on) down tight to the bales. Those straps are run underneath the toe ups and the box is pulled tight to compress the bales. Once the roof is assembled on top, it is then loaded with weight and the straps are tightened again. After a week or so of loading and tightening of the straps, the load is removed and the mesh is added to the walls.

  9. I’ll be putting the steel on the roof next week so am getting close to putting up bales. My tentative plan is to use a couple of jigs, one on top, one bale wide and built of very slick material (tempered masonite?) placed out from the boxed soffit, but at the same elevation, then another jig on the bottom that goes across the top of the second to last course and sticks out one bale, with long handels on it so as to use leverage, and again of slick material. Lowering the bottom jig at an angle will I belive give me enoughf room to put a bale on. then raise the levers to compress the bales and force it in with a large bale hammer or possibly a hydrolic cylnder. When bale is in place, pull out bottom jig.

  10. Hi Andrew. Do you have any suggestions for compressing the bales under a slanted roof? I’m building a small house with a shed roof and a cathedral ceiling, using I-joists rather than trusses. One option might be polyester strapping…

  11. If it is a load bearing house then I recommend Cord Strap, a poly strapping used for many applications. It is very strong and reasonably priced (with the ratchet to tighten the straps too). If it is a framed house, then I recommend using the method of framing the walls and top bale stop lower than the overall height of the bale walls so that the last bale course is about 2″ – 4″ taller than the space available for it. This provides excellent compression for the walls below.

  12. Thanks for the reply. You said “If it is a framed house, then I recommend using the method of framing the walls and top bale stop lower than the overall height of the bale walls so that the last bale course is about 2″ – 4″ taller than the space available for it. This provides excellent compression for the walls below.”

    Yes it’s a frame structure. Will a bale stop work if it is not exactly parallel to the bales, but slightly slanted? The roof is not steep, it’s got a 7.5° slope. Notice I’m talking about what would be the gable-end walls if this was a gable roof. Being a shed roof, it’s only half a gable 🙂

    The simplest solution is to stop the bales completely at the height of the lower end of the roof (about 8-1/2 feet). This would necessitate a triangle of frame-and-conventional-insulation on the upper part of each side of the house, which I’d really rather not do.

  13. What you describe is the best option, but you can build a wall with a gentle slope as well. It is harder to get the bales tight, but with such a low slope you should be okay.

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