Learn The Simple Straw Bale Construction Method You Can Use To Build Your House In New Zealand
One of the major things to consider when designing a strawbale building is what type of straw bale construction style you'll use. The 2 major options are either load bearing or non-load bearing. That is - the straw bale walls either take the load of the roof or a framework takes the load and the straw bales act as a type of infill.
When we completed our straw bale building workshop we learned a straw bale construction style called buck and beam. This style is most appropriate in New Zealand because of our strict building regulations. Our house designs need to be checked off by an engineer and from their perspective it is much easier to calculate the strength of a timber frame wall than a wall made purely of straw bales. There is too much variation between bales and engineers don't like to take any chances.
It is perhaps a little less "green" than a purely strawbale wall. But it is easy to build this way and easy to get it passed through council this way.
What is Buck and Beam?
Firstly - This guy in the red box is a buck...
These bucks get spaced out around the perimeter of the building (wherever there is a straw bale wall) and provide the support required to take all of the loads that will be placed on the building. They are usually placed every 2.4m and on either side of windows and doors. They are also placed in corners.
Once all of the bucks are in place they are nailed to a bottom plate (which has been dynabolted to the concrete). The bottom plate in this image is those 2 tracks of timber which are contacting the concrete. There is a layer of malthoid between the timber and the concrete to stop any moisture travelling up into the timber.
Once the bottom plates and bucks are in place they are "tied together" at the top with a box beam.
Here is a picture of the box beam sitting on top of the bucks...
It goes around the entire perimeter of the building. This beam locks everything together and gives you something to squeeze the strawbales against. The beam is filled with insulation to prevent heat being lost through this part of the wall.
We also used metal cross bracing to provide more stability to the walls. The building was quite shaky until we put these in and it felt a lot safer once these had been added. There is actually quite a bit of weight in the rest of the structure that the bucks have to support. Until the strawbales go in, it's a bit flimsy.
As you can see, it's a pretty simple structure. The rest of the framing will vary depending on your particular building. But if you can learn this buck and beam strawbale construction method, you're 90% of the way there for building a simple 1 storey strawbale structure. There are a few more details for how to install windows and doors which I'll cover in future articles. But as for the bulk of the timber framework - this is it.
If you're building something a bit more substantial like our house, it's going to be a bit more complicated. But nothing a good builder can't help you with if you get stuck.
If you'd like to learn how to build with strawbales in NZ I'd recommend getting some hands on experience in a workshop. We did one with Sarah and Sven from sol design in Geraldine. It was definitely worthwhile.