We're all very excited, nearly at the straw bale stage! First though we need to prepare...
So we've braced our window/door posts, this is to stop them bowing when the straw walls are built.
Our bales will sit on a base plate this is a timber ladder fixed directly onto the box beam. Its job is to raise the straw bales above finished floor level. Meaning that if there is a leak/spill the straw won’t get damaged. It also can provide a fixing for skirting boards.
The base plate will also provide fixings for our stubs. The stubs hold the straw bales in place. Now normally in England there are 2 quite chunky hazel stubs per bale, and these stubs are held into position in the middle of the bale with noggins.
However the noggins aren’t insulative, and therefore could potential act as a cold bridge, and will definitely reduce the amount on insulation that can go between the base plate.
Now in America they tend to hold the bales in place using nails that are only part driven in to the base plate. This is quicker, reduces the amount of noggins and therefore potential of cold bridging. But it introduced other problems, such a condensation on the nails, which can lead to decay (both of the nails and the straw).
So looking at these two methods we chose to use a hybrid method. Smaller ash (hazel is best to use, but we could coppice the ash from 5m from site!) stubs running along the ladder. Thus reducing noggin and the potential for thermal bridging, but not introducing the problems of metal within a straw wall.
In-between the base plate is ‘Leca’ insulation. This is a lightweight expanded clay insulation. It’s a good option because; its natural (it’s made by firing the clay, meaning no chemicals are added), it doesn’t degrade over time, and most importantly clay naturally wants to absorb moister. This means that if there is too much moisture within your walls, the ‘Leca’ is going to pull moisture down and out of the bales, where it can naturally leave the building due to the permeability of the materials used. As you can probably tell all the materials have been heavily though over, and where chosen as they compliment each other. Therefore in theory making a building that works in harmony and is greater than the sum of their parts….. Not unlike the interns ;)