Thanks for getting this book done! Jim, it's good to see you again after the work party down in Eugene a few years ago. That commercial structure got me thinking in a particular direction: the building had traditional framing and a permeable vapor barrier and external covering / siding. I'm about to begin work on a cabin renovation: foundation is good, roof is good, siding is ok. The location, Acme WA, gets about 65" of rain per year. I thought I'd create a similar "rain screen" as the building in Eugene. I need to re-construct some of the exterior walls and I'm messing about with a design that would use 2x6 studs that would allow me to stack bales on end between them. Each stud would create a "bay" or cavity, the bales would be stacked up the cavity and bamboo stakes would be driven into each bale pair. The 2" 2x6 could be filled with straw/render potatos/balls OR I can put the studs on 21" centers and trim both edges of each bale. The 2nd option makes me say "ugh" (even tho I found a primo bale knife at a local junk store just as you suggested). Which option would you suggest; or is there a better way? My intent in doing it this way is to minimize the "intrusion" on the interior space. Also, bale needles - do you have suggestions for making them, or having them made? I'm not a metal worker but I can't find any and the 2 fabricators I've talked with feel like I'm wasting their time with little "stuff".
Greg is referring to a commercial building project in down town Eugene, OR, that is now completed. The Mahonia building is about a city block in size, and three stories high (only the top two stories are straw bale; part of the first floor is under ground). Designed by Arkin-Tilt Architects in Berkeley, CA, the straw bales were stacked as part of a CASBA workshop back in...2017? It has exterior plywood sheathing and metal siding, and a clay plastered interior. The 3-string wheat straw bales were stacked "on end" between paired 2 x 6 "posts" set on 24" centers, but for some reason not all of the 2 x 6s were on 24" centers so we had to do a lot of bale slicing. Necessity being the mother of invention, David Arkin designed a bale slicing jig that we adapted and fussed with until we could shave inches off a bale in under 50 seconds using an electric chain saw.
Fun project! That building detail--bales on end--made it into the book, too--it's in Chapter 2 Designing with Straw Bales.
Back to your project.
I think you want to avoid custom trimming each bale unless you make a bale slicing jig like we had in Eugene. Find out what your bale size is. We used 3-string bales in Eugene because the bales we pulled from the Willamette Valley happened to be about 23” wide, so with studs on “mostly” 24” centers it was tight squeeze to force/pop them into place. I thought they were pretty tight, without much need to stuff gaps between.
I liked the method we used on the Mahonia building to secure the bales to the wall—long timber screws and plywood washers. Bamboo stakes could also work to secure the bales to one another, although I’m not clear on how that secures the bales to the framing? If you haven’t already installed the exterior sheathing you might tie the bales into the framing with baling twine.
As for baling needles, there’s a side bar in Chapter 4 Stacking Straw Bale Walls on how to make one from ¼” welding rod and a propane torch, hammer, drill, and file. Or you might search the internet. Lydia Doleman, Flying Hammer Productions (www.theflyinghammer.com) a local colleague and expert on both straw bale and light straw clay construction (see her book Essential Light Straw Clay Construction by New Society Publishers) sells baling needles—have usually have a few at every job site.
As Jim indicated, the bales-on-end between-studs approach is new and still developing. In a recent Arkin /Tit job, David let me try out a new approach to holding the bales against the stud and plywood wall: we nailed wire staples to the interior face of the studs, then looped 1/2" cargo strapping through the staples and cinched off the loops with those metal clamps. When the bales were installed the free ends of opposing straps were overlapped, pulled tight across the face of the bale with a strapping tensioner and cinched off with a clamp.
This worked really well, and is probably cheaper than using lots of those looong timber screws, but the driving reason I wanted to try it is that I'm bothered by the interior plaster having to cover alternating plywood and bale surface. Yes, the plywood washers get lathed, but it just doesn't feel right. Too close to boxing in the bales.
Final note: to make as many as possible of the spaces between studs bale width ( and avoid that bale ripping Jim mentioned ) have the carpenters NOT install Jack, Queen and cripple studs. Instead, use single trimmer studs around doors and windows and fasten sills and headers to them with clips.
You could certainly try working with aluminum rod. It's probably easier to drill into (for the needle's eye) and cut push/pull notches, but I'll note that all the bale needles I have used or seen have been fashioned from either steel welding rod or stainless steel, which--if you have the right tools--isn't that difficult to work with either. In theory, the stress on a bale needle is primarily from pushing and pulling the needle through a dense straw bale; it seems that aluminum should be able to tolerate that. Over time though, bale needles get a fair amount of bending stresses; I think aluminum is less tolerant of that.