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ECO-BUILDING – PART 8 – Framing

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

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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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ECO-BUILDING – PART 5: THE PROS OF BUILDING WITH STRAW BALES

Why build with straw bales? It can be said with great certainty that tens of thousands of people have been aroused to building their homes or other constructions with straw bales around the world. Until now, it has come to our attention that all around the world there are projects going on involving straw bale building, and the number is surely to grow with the awareness of the pros of building with straw bales.

Below are a few points which speak for the methods of incorporating straw when building with straw bales.

Energy efficiency

thermo slimAs the costs for heating and cooling rise, energy efficiency is gaining more and more attention.  It is said that a well designed and built straw bale home can lower the heating costs by 70 % compared to a conventional home. It can be considered as a significant saving.

Aesthetics

People are generally attracted to the thick walls which resemble medieval architecture or adobe homes in Latin America. A straw bale house has a totally different feel to living it, than a conventional house. The material is versatile enough to make various kinds of forms into the general building and firstly one just has to get to know the method in which way the combination of straw and other materials behave.

Acoustics/noise suppression
acoustics 004 png
Straw bale homes are remarkably quiet. The thick walls muffle sounds and diminish echoes. The most important aspects to take into consideration when planning a straw bale home is to get the correct balance of sound insulation, natural light and energy design.

At some locations around the world the technique of building strawhouses has been implemented when building recording studios. And it can be thought that workshops where noise producing machinery are operated, the strawbale walls would make conditions more bareable.

Fire rating

Homes built with straw are extremely fire resistant. A straw bale home is three times (3x) more resistant to fire than conventional homes – this is due to the fact that there is not enough oxygen in the bales for a fire to burn lively, and since the bales are covered with a thick and earthy render. In this case, one should think of a 5 cm layer of plaster covering the bales.

Environmental aspects

Millions of tons of straw is produced and burned every year. Instead, the straw can be used to produce a healthy and pleasant living environment. It also said that the amount of volatile organic compounds is less than in many other conventional buildings

See: VOC’s – Volatile organic compounds (http://en.wikipedia.org/wiki/Volatile_organic_compound)

The ease of building

Everybody can learn to build with straw bales after a few guidelines are taken into consideration. When building with straw bales, the most difficult task would be the taking into consideration of the framing, electronics,  plumbing, etc…

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