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How to build with straw bales

 

How are straw bale buildings constructed? Top tips for successful building with straw including how we built the Straw Bale Cabin and the Straw Bale Cottage.

 

Straw bale buildings offer amazing benefits. Following the main principles for successful building with straw given below, a small, simple straw bale structure could be attempted. A lot of fun would be had in the process and there would be enormous pride in the end result!

 

However, please bear in mind that careful design is needed to ensure any larger building, straw bale or otherwise, achieves its full potential. For example, consideration should be given to orientation, siting, exposure to wind and rain, solar access, insulation of all parts of the thermal envelope (roof, floors, windows), optimising heat gain, heat loss and heat retention, optimising natural light and efficient heating and ventilation strategies etc.

 

It is imperative that a good design is then carried through with quality workmanship and attention to detail. Building with a natural, breathable material like straw requires a completely different outlook. There are few similarities to conventional bricks and cement. It can be very labour intensive but the end result is well worth the effort. If more buildings were lavished with such attention, their quality and longevity would be greatly improved.

 

To quote from Tom Woolley’s book, Natural Building: A guide to Materials and Techniques,

 

“Some straw-bale enthusiasts promote the idea that this form of building can be done by amateurs and therefore little expertise is required, and, because of the many books and internet sites about it, it is easy to think that you can teach yourself; but as a result some straw bale buildings in the UK have been quite poorly designed and badly constructed since little expert help was involved. As with any other form of building, it is important to get good design and professional help.”

 

Straw Bale building is popular all around the world. There is a wealth of knowledge and experience out there and best practice is constantly developing. Make sure you get expert and up to date advice for your straw bale build. See the Home Grown Home How We Can Help page for more information.

 

 

Main principles to ensure successful building with straw bales

Please ensure that your building is structurally safe and keep your straw dry at all times;

 

1. Structural safety

Straw bales are incredibly strong but they are only part of the building. Whether building timber frame or load bearing, use the strength of the straw to good effect. Always seek the advice of a structural engineer with straw bale experience for all but the smallest of projects.

 

Bear in mind the following:

• The walls are stronger when the bales are overlapped, built like bricks with a running bond as shown in the bale plan below
• Alternate cut and folded sides of the bales to balance the density of the wall
• Insert hazel rods in the wall at regular intervals to provide stability during construction (see image one below)

 

In addition, for a load bearing design

• Ensure openings are at least one full bale length from corners and evenly spaced around the building (see image two below)
• Spread the weight of the roof over the full width of the bale walls
• Sandwich load bearing bales between an identical base and roof plate. This helps to keep the walls straight, tie them together and spread the weight. (see image three below)

 

 

2. Keep the straw dry If straw bales are kept dry, they will last indefinitely
These basic design points will help to keep them so:

• Provide a minimum roof overhang of 500mm all around the building to shed rain well away from the walls
• Raise the foundations so that the first course of bales is well away from rain splashing up from the ground (minimum 300mm)
• Plaster externally with a breathable but weather resistant render such as lime or provide a ventilated rain screen on exposed elevations
• Ensure the first course of straw bales starts above the finished internal floor level. This is known as a “toe up” and it ensures that the bales cannot be damaged by an internal water leak from pipes or appliances etc
• Keep plumbing away from straw walls if possible, otherwise ensure there are no joins near the straw or run pipes in conduit

 

 

Further tips for successful building with straw bales

 

Contact Home Grown Home, either e-mail or write to us to request these helpful pointers (free of charge).

 

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>> For more in depth research into straw bale and other natural building materials and methods see our recommended reading list, research papers or register on one of our courses (PDF).