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Building with Straw Bales
A Practical Manual For Self-Builders and Architects
By Barbara Jones UIT Cambridge Ltd
Copyright © 2015 Barbara Jones
All rights reserved.
ISBN: 978-0-85784-230-5
CHAPTER 1
Why build with straw bales?
Building with straw makes so much sense! No other building material stores as much carbon within itself, or provides so much insulation for so little cost, or is as easy to build with. So why aren't there more straw-bale houses? Partly, there is still lack of awareness about this humble building material. Partly, there is fear of something so simple and straightforward. Partly, it's because of lack of affordable land available for people of limited means but with determination and ability. But mostly, there is no profit to be made in the usual way of a business selling a product, because straw-bale building is as much about passion, about empowerment, about belief – a way of life – as it is about construction.
Straw-bale building offers us a radical way to solve many of the issues facing construction with respect to thermal efficiency, carbon footprint production, sustainable materials, durability, air quality and cost. It's far more than just a wall-building technique; it's a completely different approach to the process of building itself. Its background is grass-roots self-build: it is firmly based in that sustainable 'green building' culture that has brought to the construction industry many new and useful ideas about energy efficiency and environmental responsibility.
This method of building is now entering mainstream construction via cohousing projects, designers and architects, and community groups, which see its value in terms of cost-effectiveness, sustainability, ease of installation, air-tightness and energy efficiency. The building method itself is based on a block system, making the designs very easy to adapt from one project to another, and giving great flexibility in its use.
The accessible nature of straw as a construction material means that even those unfamiliar with this building process can participate in it. This opens the door for interest groups to work together on joint projects. Housing associations, co-operatives, and local authorities are ideal managers for self-build straw projects, which are quick to build and which will engender an excitement and motivation that gets the job done.
The atmosphere on a straw-bale building site is qualitatively different from that found on the vast majority of other sites; it is woman-friendly, joyful, optimistic and highly motivated. Knowledge and skills are freely shared, and cooperation and teamwork predominate; all these factors have a positive effect on health and safety on site.
Working with straw is unlike working with any other material. It is simple, flexible, imprecise and organic. It will challenge your preconceptions about the nature of building and the correct way of doing things – and not everyone will be able to meet this challenge. The simplicity of straw can be disarming, or alarming. If you need complexity in order to feel secure, this may not be for you. Don't be put off by nursery tales about the big bad wolf – we should be wise enough to realize that the wolf probably worked for the cement manufacturers! And there are thousands of examples of professionally finished buildings – so read on, and make up your own mind.
Straw as a building material excels in terms of its simple installation, affordability, energy efficiency, and the healthy air quality it produces. Straw-bale houses can be built to Passivhaus standards, and a two-bedroomed detached load-bearing straw house can be built by a self-builder for £50,000. Due to the buildings' super-insulation, huge savings in heating costs can be made. Potential savings of up to 75 per cent on long-term running costs can be achieved when compared with a conventional modern house. A typical plastered straw wall has a Uvalue of 0.11, more than twice as insulating as Building Regulations require. And because straw houses can be built entirely of natural materials, there is no threat from toxic materials, and no harm to allergy sufferers.
This book is aimed at self-builders and architects as well as the construction industry. It is meant to give clear and straightforward information about how to build houses with bales of straw. Since this is a simple and accessible wall-building technique available to almost anyone, it is an ideal self-build manual; it also provides information for mainstream designers and builders to design with straw, and to write specifications for sustainable house building.
Throughout this book I will be attempting to encourage you towards the best possible way of doing things with a simple, straightforward and common-sense approach. One of the best features of straw-bale building is the opportunity it provides for creative fun, and the way it enables you to design and build the sort of shape and space you'd really like. It lends itself very well to curved and circular shapes, and can provide deep window seats, alcoves and niches due to the thickness of the bales. It is flexible, and combined with flexible foundations (not as unusual as you might think) provides excellent buildings to withstand earthquakes. Its forgiving nature means it can be knocked back into shape fairly easily during wall raising, doesn't require absolute precision, and can make rounded as well as angular corners. Partly owing to its great insulation value and partly because of its organic nature, the inside of a straw-bale house feels very different from a brick or a stone one, with a cosy, warm quality to it and a pleasing look to the eye. The beauty of straw (apart from its aesthetic beauty) is that it combines very high insulation properties with great load-bearing ability: it is a material that provides building blocks and insulation all in one.
Different styles and opinions have grown up around the world as bale building has spread. What was suitable in one climate has not proved to be best practice in others, and availability and cost of materials varies from country to country. However, there have been wonderfully imaginative adaptations to conditions. Main design concerns are:
* adequate foundations to deal with moisture and insulation while impacting on the earth as little as possible;
* airtightness;
* maximizing solar gain;
* weather protection during construction;
* weather protection in general.
By going back to basics, we are able to design more appropriate foundations than became common in the 20th century, which use natural rather than unnatural materials and achieve high levels of thermal efficiency. Differences to be found in the UK are also in the predominant use of load-bearing methods and the type of render (lime) used as a weatherproof coating. In Europe we have been able to draw on the rich knowledge of the past, using ideas that have been tried and tested over centuries. In many respects, the requirements of straw-bale buildings are essentially the same as those of traditional cob (earth) or wattle-and-daub buildings. They have high plinth walls, self-draining foundations and large overhangs to the roof – 'a good hat and a good pair of boots', as cob builders used to say. They are also constructed of breathable materials and must not be waterproofed (although they must be weatherproofed). Building with straw encompasses far more than a different wall-building system, however, as the whole building can be constructed of natural materials with very low embodied energy (the energy that was used in making the product) and a negative carbon footprint, all at an affordable price.
Straw is a flexible material and this requires us to work with it somewhat differently from the way we'd work if it were rigid. Accurate measurement and precision is impossible and unnecessary with straw, but working without these aids can be worrying to the novice, and alarming to those already used to building techniques developed in the last century. However, it is very important that you have the right attitude from the outset. You have to develop a feel for the straw. You have to give it time; absorb its flexibility. It is possible to be macho about it – to hurl bales around single-handedly and force them tightly into spaces – but this always has adverse consequences. Rushing the process, and working alone or competitively can mean that an adjoining section of wall is distorted and pushed out of shape – a section that someone else has spent time and care to get right. Straw-bale building is as much a personal learning process as it is about learning a new building technique. More than any other material (together with cob and clay), it is susceptible to your own spirit and that of the team. It is not something to do alone. It requires cooperation, skill-sharing and common sense. Many of the inspirational and artistic features are created in this atmosphere. It is empowering, expanding the world of opportunities for you and making possible what you thought to be impossible!
The atmosphere and environment in which we live is a matter of increasing concern to homeowners and designers alike. There is a growing body of knowledge on the harmful effects of living long-term with modern materials that give off minute but significant amounts of toxins. The more airtight a building is, the more concentrated are the toxins. Living in a straw house protects you from all that. It is a natural, breathable material that has no harmful effects. Hay-fever sufferers are not affected by straw, as it does not contain pollens. Asthmatics also find a straw house a healthier environment in which to live. Combined with a sensible choice of natural plasters and paints, it can positively enhance your quality of life.
When building a straw-bale house, many of the other elements of a conventional building remain. The installation of plumbing, electrics, interior carpentry, joinery and partition walls may be no different from the methods and materials you are used to, though of course they could also be rethought in terms of using natural, locally sourced and recycled materials. This book covers the environmental attributes of straw; how to design an affordable house; the different types of foundation you can build without needing cement; how to build walls with straw and stabilize them; how to protect walls from the weather and make them durable; how straw performs with humidity and how straw-bale buildings can easily meet Building Regulation / Code requirements. There is also a section on frequently asked questions (Appendix 1) and a reference section for further reading, research and contacts (Appendix 2).
History
Straw-bale buildings were first constructed in the USA in the late 1800s, when baling machines were invented. The white settlers on the plains of Nebraska were growing crops in an area without stone or timber with which to build, and while waiting for timber to arrive by wagon train, they built temporary houses out of what was, to them, a waste material – the baled-up straw stalks of the grain crop. They built directly with the bales as if they were giant building blocks, with the bales themselves forming the load-bearing structure. This is known as the Nebraskan or load-bearing style. The settlers discovered that these bale houses kept them warm throughout the very cold winter yet cool during the hot summer, with the additional sound-proofing benefits of protection from the howling winds. Their positive experience of building and living in straw-bale homes led to the building of permanent houses, some of which are still occupied dwellings today!
This early building method flourished until about 1940, when a combination of war (killing off many of the most experienced traditional builders) and the rise in the popularity and use of cement led to its virtual extinction. Then, in the late 1970s/80s, Judy Knox and Matts Myhrman, among other pioneers of the straw-bale revival, rediscovered some of those early houses and set about refining the building method and passing on this knowledge to an eager audience of environmental enthusiasts. Through the green and permaculture movements the ideas spread very rapidly, with most of the new buildings being this self-build, Nebraska / load-bearing style (see Chapter 4, page 35). Before long, new techniques were developed to improve the building method, and The Last Straw journal was founded in Arizona to disseminate ideas, promote good practice, and provide a forum within which owners and builders could network.
The first straw-bale building in the UK was built in 1994, the same year that I first learned how to build with straw on a two-day women's course run by Jill Lorenzini in California. David Eisenberg of the Development Centre for Appropriate Technology (DCAT), based in Tucson, was invited to the Findhorn eco-community in Scotland in 1995 to help them build a straw-bale shed. My first straw building in the UK was in 1996, and in that year, among other buildings, I helped construct the UK's very first straw-bale home with full planning permission. This was for Brian Stinchcombe, a farmer in Wales, and you can see a video of an interview with Brian on our website here: "http://www.strawworks.co.uk/ourachievements/
I designed and helped build the first straw-bale building in Ireland in 1996, for the Steiner school in Holywood, Belfast, and there are now thousands of new structures being built annually all over the world. Just about every state in the USA has a straw-bale house, the same in Canada. There are probably close to a thousand in the UK and maybe a hundred or so in Ireland at the present time, most with full planning permission and Building Regulation approval. The UK began building with straw bales earlier than any other European country except France, which has one historic building dating from 1921. France now has 4,000 straw-bale homes with another 1,000 being built in 2014. France has overtaken the UK in the vast numbers of straw-bale houses it has because of its ample availability of affordable land, and relaxed planning laws (compared with the UK) for single self-built dwellings.
Some pioneering individuals and institutions in the UK have taken the risk to prove just what straw can do. In Stansted Mountfitchet, Essex, is a saleroom built for Sworders, a fine-art auctioneering company. It is a compressive frame style, pioneered by one of the directors, Robert Ward Booth. Originally 1,100m2 (12,000ft2) it is the largest straw-bale building of its type in the UK. It won the East of England Royal Institute of Chartered Surveyors (RICS) Sustainability Award in 2009 and in 2013 was extended to 1,600m2 (17,000ft). It was built for the very competitive price of £950/m2 (£88/ft2).
The largest UK straw prefabricated panel building was built with grant funding in Bradford, West Yorkshire, in 2011 with panels supplied by Modcell (see page 20). Designed by Waller and Partners, it is 2,787m2 (30,000ft2) in size with 14 serviced offices and 14 managed work spaces, making it the largest building using straw bales in Europe. It was built with a £3.389 million grant funding plus £1 million from a mortgage so it cost £1,575/m2 (£146/ft2) to build, using 4,000 straw bales. In 2008 another innovative two-storey load-bearing straw-bale house, built with my help between 2002 and 2005, won the Grand Designs Eco-home of the Year award. In 2009 North Kesteven Council in Lincolnshire became the first local authority to build semi-detached council houses out of straw. Straw Works designed the world's first load-bearing terraced houses, near Canterbury, built by self-builders in 2012/13.
Why use straw?
Sustainability
Straw is an annually renewable natural product, formed by photosynthesis, fuelled by the sun. Over 5.6 million tonnes are produced surplus to requirements each year in the UK. Using straw can mean there is less pressure to use other more environmentally damaging materials, and in the unlikely event that the building is no longer required, it could be composted afterwards. It is extremely low in embodied energy at 0.91MJ/kg compared with a concrete block with an embodied energy of 4.6-5.6MJ/kg and has a seriously negative carbon footprint, storing carbon in its fabric for the lifetime of the building. For houses that last upwards of 100 years, this is extremely significant for helping revert the emission of greenhouse gases.
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Excerpted from Building with Straw Bales by Barbara Jones. Copyright © 2015 Barbara Jones. Excerpted by permission of UIT Cambridge Ltd.
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