ANCHORING BALES TO POSTS
If you build your straw bale walls without the use of mesh on either side of the wall, you will need to attach the bales to the structure in some other way. The most common is shown in the image to the right and involves cutting 4″ wide x 12″ long (or so) pieces of plaster lath and nailing them to the posts at the top of each course.
The lath is then folded down over the top of the bales and attached with landscape pins. This works well and, again, is necessary only if you do not attach the bales to the structure by way of welded wire mesh or stucco wire sewn from one side of the bale wall to the other.
A newer option for attaching the bales is the use of expansion foam in the voids created around the notches at each post location. By shooting in a little expansion foam, the bales will be attached to the structure in a way sufficient to withstand movement during the plastering phase; however, this is not a structural connection, so you must not rely on it to withstand any lateral or out of plane forces applied to it. The foam is a faster way to connect the bales if all you need is a temporary fix while you wait for the plaster to lock everything in place.
3 Responses
there seems to be a broken link with the bale-attachment jpeg.
Thanks. I got it back now!
We used expanding foam, which makes a great mortar. We pounded nails halfway in on the posts and beams before laying the bales, then used the foam where the bales had been notched; the protruding nails add extra grip. We also squirted foam at all the bale intersections. I know you say this isn’t structural, but you could run into the wall with your shoulder afterwards and it was pretty darn solid. Nevertheless, we also sewed each course of bales to each post using polyester strapping.
We kept the foaming step behind the bale-laying by several courses, in case anything needed to be re-laid. I don’t know if you’ve ever tried to break apart two bales that’ve been foamed together, but it’s pretty hard to do!
I was worried at first about this not being very green. But my house plans specified metal along every course of bales, similar to what you describe, so maybe in the end it’s kind of a wash, if you look at the manufacture of foam versus the manufacture of all that metal. There are only two of us building the house so the walls will have months to offgas any residual fumes before plastering.
The disposable cans of foam are expensive because once you open a can, you’ve got to use it up or throw it away. We got a pro gun and bought foam by the case, greatly reducing the cost.