ECO-BUILDING – PART 9 – Custom bales

A lot of custom trimmed bales are required in any straw bale home. The areas with windows serve as good examples. The task is to make a rectangular bale to fit. During the process one needs to know how to cut and retie bales, and how to notch and shape them.


The tip of a baling needleCutting the bales is not as easy as one would think. A bale of straw cannot be worked on as one would work wood. The bales have a tendency of breaking apart if not worked on in the correct manner. When working with bales one has to mark the bale where one wants a cut to be made and then proceed cutting the bale while incorporating a tool called a baling needle to retie the bale in parts where one will not be cutting the bale.

With a good baling needle you can retie a bale and create two custom bales from one in a short amount of time. The most important knot to know here is the Miller’s knot.

Notching and shaping

Notching and shaping require the use of a chainsaw and a can of spray paint to make the markings of where you need to cut. Notches might be needed to fit the posts and other framing components. A time-saving method is to slightly over-cut the needed part for the posts and then stuff the space with straw if needed. Be careful not to cut the string of the bales while notching. Some notches can be more intricate than others.


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Post and beam systems

Straw bale building are not the same as conventional buildings. This is an advantage and precisely the reason why some people incline to building straw bale houses. The best thing to do is to use framing systems which are adaptable to the bales found for your build. For most non-bearing systems, the framing is a post and beam or a modified post and beam frame.

In a non load-bearing construction the whole strength of the home is in the construction itself. This provides a load path for the roof and floor systems. It also acts with the shear strength for the building. This system holds the house up.

A similar value can also be given to the bales and the sorts, even though the frame is often regarded as the actual structural system.

Special considerations

Mesh used to reinforce the surface renderUsually a conventional frame is to be changed for straw bale purposes in a number of ways. First, there needs to be enough room for the adequate nailing of the lateral shear mesh around the doors and windows. For making this, an additional trimmer may be required depending of the inclusion of the exterior trim. There also has to be enough nailing surfaces along the base of the wall system for a possible mesh to be used.

Framing layout

Unlike conventional construction, the framing does not land on four foot centres and in four foot modules to accommodate plywood sheets. Instead, the layout of framing is designed to fit the size of the bales and support the calculated loads. The more accurate you are with framing to the bales sizes, the less you will have to do during the baling stage. It is also important to pay attention to the header and plate height around the house. The goal is to fit the bales tightly under the top plates to help squeeze the bales and strengthen the wall. The windows and door header heights should be lined up so that numerous layers of stuffing are not required to continue the running bond of the bales.

Roof design

Hip roofRoof designs do not change that much to the conventional roof. When making a gable roof, more custom made bales have to be used, and some designs require more work to be adapted to a straw bale home. As an example: In a gable roof design, more custom-made bales have to be made, as one builds more towards the roof line.

Gable roof


A roof design can also help diminish the darkness sometimes created by the thick straw bale wall. By making an open roof design or dormers, more natural light can reach the room, thus brightening a room that may otherwise seem dark due to window size and orientation. The roof overhangs are should be quite remarkable in order to protect the construction from rain and/or snow.

Toe ups

The creation of toe ups is a part of the framing process. In a straw bale construction, toe ups are a necessary part of the straw bale construction. They provide adequate nailing surface for the possible wire mesh and separate the bales from the concrete and create a so-called moisture break. Should there occur a water break, the toe ups keep the bales dry and protected. The toe ups can be constructed using pressure treated 4×4 material, gravel and tar paper. They also provide a foundation or base for the bale anchors, which are required by code in various countries. The bales are attached to the toe ups, and the toe ups are attached to the concrete. In this way, the entire system is anchored to the foundation.

Some code books require the use of re-bar impalers for the system, but some nails applied to the toe ups have also been accepted in certain areas. The nails create a much stronger connection for the bales and do not interrupt the separation of the bales from concrete the way a rebar sections buried in the concrete does. Many building departments have easily accepted this kind of change in the construction.

Straw bales stacked on toe ups in a construction

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Once you have gathered some knowledge of the land and a design which you have found appropriate, the origin of the bales is to be found out.

It would be helpful to know exactly how big the bales are, and which kind you are going to supplied with – and at least their approximate dimensions. This is crucial during the design and engineering of the framing.
There are many farmers with available bales, so there is also a lot to choose from. Do meticulous research on the quality aspects of the bales. The difference in price does not vary that much, and this little extra effort is worth its while it in the end.

Visual inspection

strawbalesThe colour of the bales tell a lot of the history of the bales: If they have seen weather or not? Have they been stored properly? If there is a lot of white powder coming from the bales when they are agitated, it can be considered as interior mold. This can also be judged by smell; in the case of mold, the smell is unmistakably musty.
If the the visual inspection reveals that the bales damaged by water, moldy or otherwise not in good condition, it is advisable not to use the bales in the construction because then the whole construction would be placed into jeopardy.

Bale density

One important factor when choosing the bales is the density of the bales. Most building codes which recognize straw bale construction commonly require a specific density for the bales.
Calculating the density in some regions is usually calculated by the dry density of pounds per cubic foot (1.10 kN/m³).
It is essential to know the density of the bales in order to guarantee the building inspector of the quality of the bales.
A field test can be conducted in order to make sure of the density of the bales.

Moisture content

moistureThis might be most important factor when choosing bales. If the moisture content reaches over 20% , this level is enough to give a habitat for mold and decay. It is difficult to reverse the process of mold and the process produces two things the bales need to rot: moisture and warmth.
When measuring the moisture of the bales, keep in mind that the bales take and lose moisture in relation to the ambient moisture. When reading the moisture content, the reading should come from the bales and not the atmosphere.
It is not recommended to measure the moisture content in the early morning, when the dew may affect the reading.

straw baleQuestions such as what science do the local codes require in making the decision also have to be answered. And furthermore, it is much more desirable to have the straw bales from the local area for the building to have a lower impact towards the environment.

After you have found a suitable supplier concerning the bales you can move on to the next phase of designing and construction.

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Design Styles

Before the final decision is made, many variables have to be considered before that final design, such as weather conditions. If there is a lot of rain in the location – either seasonally or throughout the year – a home designed for a place which gets little or no rain may not be the appropriate option for the design. The style and details of the design is important for the efficiency of the home, so this should be considered thoroughly and with time. This is a process which should not be rushed and the characteristics of the property should also be taken into consideration.

Visiting and evaluating the site and property

It can be considered vital to understand the property before and during the design-process. If there are no hurries in the design, one has the opportunity to study how the land interacts during the year. One could discover later on during the project that the location is a wind tunnel for most of the year or that some other place would have suited better in terms of solar power and ventilation.

All this is found out through experience.

Water considerations

Pay attention to how the water flows on the property. Study if there are any bodies of water which are influential to the planning and find out how they behave. What is the situation of the ground water? – and if you are not connected to the network of the city, what are the possibilities of building a well?

Some points to consider are also the leach field for the septic system, and where and how the grey and black water is treated.

The well for drinking water must be situated a safe distance away from these and it might be best to keep the well uphill from the drain field where waste water is drained to. These are one of the reasons why topographic knowledge of the topography is essential in the planning.

In addition, a possible field should be close enough to minimize costs.

Solar trackingsolar panelo and sun

The sun is vital for an efficient home. It is possible to harness the suns energy for electric and heating needs. How does the sun behave towards the land during the different times of the year? These points affect the size and need for the roof overhangs of the building and the placing of solar panels. Further investigating comes in regarding the trees, prevailing winds and the sloping of the land.

Other aspects on design

When you know your land and the positioning of your house, it is time to start designing. Pay attention to window placement and size, since these affect the heating costs. Straw bales are ideal for sound proofing and for insulation, so this information with additional info on light and ventilation creates balanced results.

It is more economical to design with the land: taking in mind to topography, water wind, the possibilities with solar issues and flora. It is also more beneficial to take into consideration to have the home as a part of the landscape.

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