The size of straw bales is an important thing to think about when building a straw bale house. Straw bales vary in size and shape. Straw can be purchased in large round bales which are of little benefit in construction, although they would make a magnificent pillars at the front of a mansion. That I am yet to see.
The largest bales of straw for sale in Australia are the 2.4x 1.2×1.2 meter (8’x4’x4’) jumbo bales There are also large bales of straw for sale that are 2.4×1.2x.900 meters (8’x4’x3’) and 2.4×1.2x.600 meters (8’x4’x2’). All of the jumbo bales require mechanical lifting to transport and position them into the structure. When using the jumbo bales in construction the bales are laid in the wall with the stalks vertical, whilst the smaller two string bales can be laid on flat or on their edge.
The most common bales used in Australia are the two string bales, which are approximately 900mm long x 450 mm deep x 350 mm high when, stacked on flat. The standard two string bales are easily handled, weighing approximately 16 kg. You will have little difficulty positioning them in the wall. Most of the women that attend our straw bale house workshops have little difficulty handling the straw bales. It is important that appropriate scaffold be supplied when installing a bale at the top of the wall, as whilst their weight is manageable, it can easily put you off balance.
When the straw is fed into the baler it is picked up and inserted into the chamber in which the bale is pressed with a large fork like object referred to as the magpie. As the magpie forces the straw into the chamber, the straw on one side of the bale is bent to enable it to go into the chamber, whilst the other side is cut with knives as part of the operation. The side of the bale that has the bent straw is slightly thicker than that of the cut side of the bale. This needs to be taken into consideration when laying the bales, otherwise the straw bale wall is likely to bow or even collapse during construction. The cut side of the bale, the thinner side, is easily distinguished from the folded side of the bale. The folded side of the bale will have a fluffy appearance, whilst the cut side has a sharp clean surface where you can actually see the end of the stalks of the straw. The tightness of the bale is controlled by the operator of the baling machine, as is the length of the bale.