Straw requirements for straw bale construction

Whilst it is possible to build a house with bales looser than ideal, it will dramatically increase your work load. You will have to spend a considerable amount of time straightening the wall once you have assembled the wall, as well as considerably greater effort during compression of the wall to ensure that you end up with a stable wall which has structural integrity.

Handling loose bales is difficult, as the twine around them is inclined to come off the bale leaving you with a pile of loose straw. This loose material can be used to fill holes between the bales once the wall is built, and can be used for making cobb (a mixture of loose straw and render.) You will have plenty of loose straw after cutting bales with introducing extra as a consequence of faulty materials.

The length of the bales can vary from 800 mm up to 1200mm. Ideally you want them to be twice as long as they are wide, as this will make it much simpler when laying bales around a corner, as it enables you to more easily maintain the correct alignment of the vertical joints between bales.

Ensure before taking delivery, that the bales are dry on the inside. It is worth wasting a bale or two the check this rather than to have a truck load delivered that are only good for mulch on the garden. If they have been wet to the point of concern, it will have a darkened appearance and may have black spots of mold. If they are dry but have a darkened appearance and/or have black spots it is indication that they have been too wet in the past. It is best to give someone else the opportunity to buy them.

A simple test for appropriate firmness of the bale is to lift it by a single string. If the twine does not come off the bale it will probably be fine. If you are unsure it is best to keep looking. Do not go against your gut instinct.

Material baled before 10AM in the cool of the morning is much better than in the heat of the day. Before 10AM the moisture in the stalks will enable them to bend rather than to crack and break when they are pressed into the baling machine. This will lead to a significantly stronger and more stable end product, which is ideal for construction. If you are purchasing material direct from farmers, explain to them that you require material baled with moisture in it but not wet. Explain to them the reason behind this so that they understand that there is a valid basis for the requirement. You will find that most farmers with experience in this field will know that it is best to bale in the morning, however time and money pressures now days often force them to work outside of what is best. When you open the test bale you will quickly see if the stalks are broken as opposed to bent, which will indicate what time of day they were baled.

If you purchase from a supplier who says they are appropriate for house construction, I am under the impression that you have some protection under the trade practices act. It is my understanding that act says that a supplier is required to supply product appropriate for the known use of the product. Obviously you would need to inform the supplier what you are going to use the product for if this were to come into play. If you are going to rely on this I would suggest that you seek legal advice. Do NOT take my word for it as I am not licensed or qualified to supply legal advice.