A brief look ahead at our natural building courses for 2018

Attend our natural building course and take the first step to a sustainable future by learning hands-on natural building skills. Learn a whole range of materials and techniques while exploring questions around sustainable living based in Peter McIntosh’s experience living off-grid since 1999.

Natural building courses in South Africa 2018

If you’re serious about building naturally and sustainably then you’ll know that each technique has pros and cons. That is why our natural building course is designed around the principles of understanding earth, how it works and does not work together. You will leave with the theoretical understanding and practical grounding of a range of techniques and materials, so that you are able to make the most appropriate decisions regarding materials and or sustainability once you are ready to begin your project.

This year, Peter will be hosting two CPD accredited courses at Jakkalskloof farm, in Swellendam. Continue reading

https://www.naturalbuildingcollective.com

First natural building course of 2016

Announcing our first natural building course for 2016! Our natural building course is comprehensive and covers a range of materials and techniques based on Peter McIntosh’s professional and personal experience working with these approaches and from having lived off-grid since 1999.

The course will be taking place at Wild Spirit Backpacker’s in Nature’s valley from 17 – 23 April. You will leave with the theoretical understanding and practical grounding of a range of techniques and materials, so that you are able to make the most appropriate decisions regarding materials and or sustainability once you are ready to begin your project.

Drop us an email to book your place and avoid disappointment.

Poster 04_2016 sml

https://www.naturalbuildingcollective.com

TERRA Award ~ first international prize for contemporary earthen architecture

The TERRA award is a collaborative effort on an international scale to enable both professionals and the general public to fully appreciate earth’s increasing popularity as a building material of high aesthetic and technical quality. 

Earth is becoming increasingly popular in contemporary architecture: hundreds of projects of high aesthetic and technical quality are emerging across five continents. This material, which has low embodied energy, is readily available and appropriate for participatory buildings. It could help provide a solution to the needs for ecological and economical housing.

To enable both professionals and the general public to fully appreciate this building material, the following partners have taken the initiative, under the auspices of the UNESCO Chair “Earthen architecture, construction cultures and sustainable development”, to launch the first international prize for contemporary earthen architecture: the Labex AE & CC-CRAterre-ENSAG Lab research unit, the amàco project, the Grands Ateliers, the CRAterre association and EcologiK/EK magazine.

Wang Shu, 2012 Pritzker architecture prize laureate, is the president of honour of this TERRA Award, the trophies for which will be presented in Lyon on July 14, 2016 at the Terra 2016 World Congress.

Context

Since its creation in 1979, the CRAterre-ENSAG Lab has been considered as the international research and training reference centre for earthen construction. It will organize in July 2016, under the auspices of the UNESCO Chair “Earthen architecture”, the Terra 2016. This World Congress takes place every four years on a different continent and will be held for the second time in Europe. It is expected to draw around 800 professionals, teachers and researches to Lyon (France).

The TERRA Award was initiated within this framework. It will be the first international prize for contemporary earthen architecture and a natural furtherance of the national award launched in 2013 in France by CRAterre-ENSAG, AsTerre and EcologiK/EK magazine.

Objective

The purpose of the TERRA Award is not only to identify and distinguish outstanding projects, but also to highlight the audacity of the project owners for choosing to use earth, the creativity of the designers and the skills of the craftsmen and entrepreneurs.
An itinerant exhibition will feature 40 buildings from all continents, constructed using various techniques (adobe, cob, CEB, rammed earth, plaster, etc.) for all types of programs: housing, public facilities, activities, and exterior and interior designs. The exhibition will be completed with lectures and workshops by CRAterre-ENSAG and the amàco project.
The search for outstanding achievements deserving of this prize and the associated exhibition will make it possible to generate the first worldwide database on contemporary earthen architecture. The resulting virtual library will be available both to the general public and professionals via this website.

Involved projects

The projects must have been completed after January 2000.
There are eight categories covering all types of programs, whether new or renovated:

  • Individual housing
  • Collective housing
  • School, sports and health facilities
  • Cultural facilities and religious buildings
  • Offices, shops and factories
  • Interior layout and design
  • Exterior design, art and landscape
  • Architecture and local development

Text from the Terra Award website.

https://www.naturalbuildingcollective.com

How to incorporate passive solar design in your building, using thermal mass and insulation.

Passive solar design can dramatically reduce our demands on fossil fuels and other forms of energy input, allowing our buildings to become producers and not consumers of energy and resources, supporting us in a healthier more comfortable abundant way.

DSC01797_edit 1

Passive solar design is the starting point of sustainable building. Once one understands the basic principles of using the abundant natural renewable resources at our disposal we become more creative in our approach to design, more in tune and observant, reconnecting us with the natural rhythms that surround and sustain us, if only we would pay attention. Sustainable buildings save money, reduce your carbon footprint and provide a healthy living environment, transforming buildings from consumers of energy to producers and forging buildings that meet our needs.

From a permaculture perspective, incorporating these aspects into the design of your home are excellent examples of several permaculture design principles. To mention the most obvious: Observing and interacting with your environment to make the most of the sun’s migration, catching and storing energy, using and valuing renewable resources and services, integrating functions and elements rather than segregating them and obtaining a yield from the planet’s most abundant energy source, the sun.

Passive Solar Design uses the energy provided by the sun and stored in the earth. First we need to look at how this energy is utilized by defining insulation and thermal mass and then look at the strategies of how to incorporate them into our designs.

Continue reading

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Owner-builder journey ~ Franz Muhl: Energy flows where attention goes

In this edition of the Owner-builder journey, Franz Muhl writes about a mud brick addition to his Scarborough home: “Let me build a home from fertile materials that is beautiful and healthy to live in, have a very low footprint and would grow a forest if you left it.”

Franz 1

Five years ago, Peter McIntosh gave me +- 900 sun-baked mud bricks, for an extension to my house. Franz 3With little start up money, a trickle of income, some plans on google sketch up, a pickaxe and, most importantly, plenty of time, I finally started the process a year ago.

 

At foundation level, with the skills that I had at the time, I used clay-fired bricks and a bitumen coat for damp-proofing. Franz 4In March, I headed off to Berg-en-dal for a crash course with Peter. He traded his skills and knowledge in natural building for mine in brewing beer. To take clay, sand, water and a bit of straw in the right proportions and work it into a material for building, was a big revelation for me. Continue reading

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CPD accredited natural building course: Materials and techniques

Our natural building course is comprehensive and covers a range of materials and techniques based on Peter McIntosh’s professional and personal experience working with these approaches and from having lived off-grid since 1999. You will be empowered to be successful and make rational choices whatever the given situation.

We’re excited to announce the first course of the year will be taking place from 26 April – 2 May, at Wild Spirit Backpacker’s lodge in the beautiful Nature’s Valley.

Take the first step to a sustainable future by learning hands-on natural building skills. Understand the alchemy of how different types of earth work, and do not work together, their potential and limitations. You will also explore questions around sustainable living based in Peter McIntosh’s experience living off-grid since 1999.

Email naturalbuildingcollective@gmail.com to book your spot!

CPD accredited Natural Building 7 day course_April_WS

 

 

https://www.naturalbuildingcollective.com

Lebone Village launch

Imagine being outside on a chilly Free State winter morning with the sun just coming out and starting to gently warm your body. Now imagine being told to take off your shoes in order to trudge in icy cold mud. I glanced at my fellow volunteers and I saw a collective dissent quietly dawn on our group – this is not what we signed up for!

Mandela day

It was the morning of 18 July, Mandela Day, and we were all gathered at Lebone Village on the outskirts of Bloemfontein to volunteer our 67 minutes for the orphans. We were standing in a circle around Peter McIntosh, who was valiantly demonstrating to us the endeavor of making adobe bricks.

Peter McIntosh demonstrating how to make cob

Peter McIntosh demonstrating how to make cob

The mix using ingredients easily available for the project was chosen after rigorous testing. According to Peter, the mix will differ in every situation, depending on the composition of the ingredients used. The chosen mix for the adobe bricks at Lebone Village was as follows: collect two parts red earth, 2 parts sand with rubble, one part fine sand and two parts water in the centre of large piece of 25” thick canvas material.

Now mix it all into clay with your feet by walking back and forth through the cold, wet mixture. When the cob mixture starts to flatten out, pull the canvas up-and-in towards you from the corners to bring the clay mixture back into the centre of the canvas and into a manageable heap. Now start stepping onto it again. The clay is the right consistency when you can make a ball with your hands and pull it apart into two separate pieces without it crumbling. Adding straw to the mud mixture assures bricks that are well insulated against cold and heat, the more straw you add, the better insulated your bricks.

Adding water

Adding water

Adding straw binds everything together and adds insulation value

Adding straw adds insulation value

Lots of people turned up

Lots of people turned up

 

While the majority of us were still apprehensively contemplating the prospect of braving the cold and mud with naked feet, one person rose to the occasion without hesitation. In the spirit of “first being a follower in order to be a leader”, Itumeleng Santo started pounding the mud into clay with some über cool dance moves. Itumeleng is an out-patient at the University of the Free State’s Dept of Occupational Therapy’s clinic at the MUCPP offices in Rocklands location. He is severely impaired due to a brain injury that he suffered during an assault. For Itumeling, taking part in the Mandela Day activities at Lebone Village was therefore also a day of getting therapy without being given therapy. The Dept of Occupational Therapy vision is to support and treat their disabled and impaired patients in such a way that they will be able to return to their families and communities and be able to fully participate in community activities again. The aim is for such patients to become fully functional individuals who can partake in economic activity and contribute towards their own livelihoods.

The MUCPP clinic of the Dept of Occupational Therapy is not only for patient care and therapy, but it also serves the wider community as a place where youth can hang around after school and in this way be kept off the streets. Heidi Morgan and Bronwyn Kemp, who run the clinic, aspire to teach these children skills that will help them to create their own employment upon completing their school careers. Learning how to make adobe bricks and tire pounding for alternative and natural building practices are two such skills.

This notion of self-empowerment of the impaired, disabled and destitute was the golden thread that ran through the activities at Lebone Village on the morning of Mandela Day. Stakeholders from support institutions to the disabled came from all over the Free State region to learn the new green building techniques of making adobe bricks and pounding tires. These are skills that they intend to take back to their home towns and villages, skills that they hope will enable them to become self-sufficient and self-employed, able to earn money and make a living for themselves, without being a burden to their families.

Getting our feet dirty

Getting our feet dirty

Peter McIntosh demonstrating putting cob into the brick mold

Peter McIntosh demonstrating putting cob into the brick mold

With the ice now literally and figuratively broken by Itumeleng, the rest of us started to get into the spirit of the day. The extra brave ones took of their shoes and started pounding cob with their bare feet. The more modest traded their shoes for gumboots to get the job done.

Some started working the cob with their hands. Anita put on some vibey music and soon the day was in full swing. Volunteers started forming little groups, each group working their cob on their own piece of canvas. Some people would collect the pounded cob and compact it into wooden molds set out by Peter for this purpose. These mudbricks would then be left to dry in the sun for several days, where after they will be ready to use for building.

Peter McIntosh demonstrating putting cob into the brick mold

Peter McIntosh demonstrating putting cob into the brick mold

The teaching of green building techniques to the greater Mangaung community also served as the launch of the Lebone Village Climate Resilient Arts, Crafts and Cultural Hub and was initiated by Qala Phelang Tala, a non-profit organization based in Bloemfontein and associated with the Centre for Development Support at the University of the Free State. Qala Phelang Tala is Sesotho for “Start Living Green” and is the brain child of Anita Venter, a researcher at the Centre for Development Support. QPT strives to empower “change agents” through social entrepreneurship in order to create systems addressing housing, food security, water efficiency and energy independence that are resilient to climate change. Their slogan is “Learn by doing!” This means that they not only preach green building and sustainable, environmental friendly living, but they also practice, implement and teach these techniques. QPT head hunted and hosted Peter McIntosh from Natural Building Collective, who is one of only a handful of natural building experts in South Africa. His experience in sustainable living practices includes sustainable agriculture, off-grid energy systems and an array of natural building techniques, all of which is in fruition on Berg-en-Dal outside Ladismith in the Klein Karoo, a farm owned and managed by the community and educational non-profit the Klein Karoo Sustainable Drylands Permaculture Project, where he is a resident and member.

Some of the mudbricks that were made on the day drying in the sun

Some of the mudbricks that were made on the day drying in the sun

Contributed by Amanda de Gouveia on behalf of QPT. Photos courtesy of QPT. Please visit their Facebook page for more photos of the day.

Amanda de Gouveia

Amanda de Gouveia has been a research assistant at the Centre for Development Support at the University of the Free State since 2010, where she has mostly been involved in research projects on social development and local economic development. This has refined a unique repertoire of research skills, both qualitative and quantitative. She has also Masters degree in Research Psychology.

 

 

https://www.naturalbuildingcollective.com

Understanding Earth II: Testing earth

By Peter McIntosh

(Please note that in order to understand what is written here you will need to have read my previous post on understanding earth)

 

Earth requires two properties to make it strong enough for building, compressive and tensile strength. In much the same way that steel works in concrete they can’t be looked at in isolation as they work together. For example, even though concrete when supported can take an enormous amount of pressure / compression without disintegrating, if you were to cast a concrete lintel without steel and suspend it between two points and apply pressure / tension, it would snap. Steel has enormous strength in tension while concrete has enormous strength in compression.

Compressive strength is measured in Megapascal (MPa). One atmospheric pressure is 101 325 Pascal; a Megapascal is more-or-less one million Pascal, or 10 times atmospheric pressure. In other words, one MPa is 10 times stronger than it needs to be to resist the force of gravity on earth, stand on its own and not be crushed.

A good mud-brick has a MPa strength of around 1.6 to 1.9 MPa, while a clay-fired brick has an MPa strength of around 14. Concrete ranges between 15 and 25 MPa. Obviously these figures vary widely, but these are good averages. A mud-brick at 1.4 MPa is 14 times stronger than gravity, a clay-fired brick at 14 MPa is 140 times stronger than gravity or 140 atmospheric pressures.

Tensile strength is found in all material, just in varying degrees. Concrete as we have seen has high compressive strength but relatively low tensile strength. The addition of steel (reinforced concrete) increases its tensile strength. Mud bricks can handle 14 atmospheres, but like concrete they have poor tensile strength. However, as clay is somewhat plastic in its behaviour it’s not as poor as one may think. This is why the addition of straw to a mud brick is essential as it not only increases the insulation value of the mud brick but also acts like steel in concrete. (I am told that weight-for-weight straw is stronger than steel or at least in the same realm.)

In short, the tensile strength of a material is its ability to resist snapping and cracking. Increasing the hardness of an earthen material, for example by adding lime, may not increase its tensile strength or resistance to cracking, as it may end up becoming less plastic and more brittle. Thus, clay buildings are often more resistant to cracking because they can absorb the movement that harder more brittle materials may not.

When building with earth, strong enough is what you are aiming for. At 1.3 MPa, a double-storey building is already seven times stronger than it needs to be. However, given window and door openings and the fact that the gravitational forces need to be transferred around them, 1.3 MPa just covers it with a safety margin. It is important to grasp that it does not matter at all if you used clay bricks at 14 MPa, once something is strong enough, the extra strength means nothing at all.

Testing of the material

Tensile testing

–          Make a brick using the cob method (that is using sand, clay and straw ) and a 2 litre ice-cream tub as mould. Number each mix and mark your bricks and balls.

–          Allow the bricks to cure for 3 weeks minimum in the sun. A brick is considered cured after 3 months, but I have found that 3 weeks gives you a really good idea, after all it will only get stronger.

–          Drop the brick from waist height, onto a very hard and flat surface and observe how it breaks up. If it shatters it is no good; breaking into a few large pieces is acceptable. Often enough it does not break at all, which is fantastic.

A failed tensile strength test after being dropped on a hard surface; the brick should not disintegrate. Four big pieces is just a pass, but one is happiest when the brick bounces and does not break at all. This often happens.

A failed tensile strength test after being dropped on a hard surface; the brick should not disintegrate. Four big pieces is just a pass, but one is happiest when the brick bounces and does not break at all. This often happens.

Observe the cracking. Surface cracks, no deeper than a centimetre are fine. Cracks that run deeper compromise the material. They may be due to a very aggressive clay or because there is too much clay in the material. There can be other causes of the cracking such as the addition of too much water or uneven drying of the material.

Compressive testing

–          Make tennis ball size balls using the cob method and allow to cure, as above. A ball has a point and you are testing the point load. Remember to mark the balls.

–          Place the ball on a hard and flat surface. Stand on the ball with your heal and slowly increase your weight on the ball until all your weight is suspended on it.

My weight is around 80 kg and I know that if the ball crushes just before all my weight is suspended the MPa strength is 1.3. If it takes all my weight then the MPa strength is at least 1.4. As you gain more experience and your frame of reference increases you can quite accurately gauge greater MPa strengths by gently bouncing with your heal on the ball. At around 1.8 MPa the balls are very resistant to crushing with the heal, even with repeated bouncing; but then it does not matter because the material is already more than strong enough.

Both the compressive and tensile strength tests need to be passed for the material to be good enough to build with. Of course, if the material fails these tests it does not mean it can’t be used, especially if cracking is the result of failure. You can try excluding water and instead try ramming the material as a way of lining up the particles and see if that will works; or try making compressed earth bricks or even a sand-bag house?

Bottle, tongue and touch are all good indicators of how an earth is composed, but nothing beats compressive and tensile testing.

Bottle: place 4 cm of the earth in a 400ml bottle, add water and a teaspoon of salt to help it settle and shake it all up. It will give you an indication of the particle ranges you are dealing with and their ratios. However beware you will not be able to tell the difference between sand and silt.

To check if clay is present, make the material very wet and rub between your hands, then dip your hands in water, if the material sticks then there is clay present if it falls away then there is mostly or only silt.

Resistance to water erosion is dealt with separately in the plaster stage which will be dealt with later.

Below is a list of tests I made for Magic Mountains retreat as an example of a comprehensive earth test.

First walk the area you have to source your materials and then collect samples from various sites. Here I located 2 distinct earth types. White building sand was located close to the farm. Make observations of the material so you can begin to make rational choices for you mixes.

Earths ready for blending at Magic Mountains Retreat. Note the 2 litre ice-cream container for making a brick.

Earths ready for blending at Magic Mountains Retreat. Note the 2 litre ice-cream container for making a brick.

Red earth located in the South East corner of the property. This earth appears to have a high clay content. It is also attractive in colour. Made up of fine sand clay and unspecified amount of silt

Brown earth located to the North. This earth appears to have a higher sand content although very fine. Certainly has a lower clay content than the red earth.

White sand located to the South on a neighbours farm. This sand has a particle range that excludes finer particles and is angular and not rounded.

The following test samples were made to deduce the tensile and compressive strength of the material, clay content of the red earth, and cracking of the material will also be noted:

A100: 3 x 2l 100% earth bricks red earth and test balls

A100: 3 x 2l 100% earth bricks red earth with straw and test balls

3 x 300mm x 300mm x 170mm red earth bricks with straw

 

B100: 3 x 2l 100% earth bricks brown earth and test balls

B100: 3 x 2l 100% earth bricks brown earth with straw and test balls

3 x 300mm x 300mm x 170mm brown earth bricks with straw

 

50/50: 3 x 2l earth bricks 50%/50% red and brown earth and test balls

50/50: 3 x 2l earth bricks 50%/50% red and brown earth with straw and test balls

2 x 300mm x 300mm x 170mm 50%/50% red and brown earth bricks with straw

 

W80: 2 x 2l earth bricks 20% red earth 80% white sand and test balls

W66: 2x 2l earth bricks 33% red earth 66% white sand and test balls

W50: 2 x 2l earth bricks 50% red earth 50% white sand and test balls

 

C4:     2 x 2l earth bricks 50% red earth 50% sand and test balls

C66: 2 x 2l earth bricks 33% red earth 66% sand and test balls

 

2x compressed earth bricks from red earth

The completed bricks and balls should be left to cure in the sun for at least 3 weeks, and turned a few times to ensure even drying whilst keeping an eye on the weather.

The completed bricks and balls should be left to cure in the sun for at least 3 weeks, and turned a few times to ensure even drying whilst keeping an eye on the weather.

The bricks ready to be tested on a hard surface

The bricks ready to be tested on a hard surface

Results of the brick testing above

It was established that the red earth has a high clay content. Certainly above 60% as the bricks with 20% red earth and 80% white plaster sand were only just below minimum building strength. As soon as the ratio of red earth reached 33% it was obvious that the bricks passed both a compressive and a tensile strength test. It is estimated that the MPa strength at 33% is 1.4. Above 33% red earth and the bricks harden a lot.

The brown earth from below the dam could be used as a filler with the red earth, but this was decided against as it is in valuable agricultural land. It is not suitable on its own.

The addition of straw added to the tensile strength of the material in all cases.

The red earth bricks displayed deep cracks indicating a high clay content, once 50% sand was added the cracking was acceptable. The addition of sand will ensure that this does not happen and is a good enough reason to not use the red earth on its own.

The tests done with the white sand and red earth were strong enough from 33% red earth. A second test was also done with 50% red earth and 50% white sand which delivered a brick over 1.6 MPA.

 

Compressed earth bricks using red earth only, are strong enough and has no cracking. It is interesting to note that the red earth was suitable as a building material on its own if it were not for excessive cracking due to the swelling of the clay with water and that if one uses compression as a method of lining up the particles and so exclude water the earth can be used as it is.

It was decided that, because the white sand was easy to access with little environmental damage and because it would eliminate cracking, that the addition of 60% sand was the most favourable option; 40% red earth just to remain clear of the 33% mark that we know is good, in case the earth varies slightly. So 60% white sand and 40% red earth.

A series of tests made in Groot Marico. All these tests passed and although the red earth was most attractive it was decided to go with the brown earth as the red earth was further away and good for agriculture. The red earth was however used in the final plaster coat where the quantities are very small and not in the walls themselves. When a number of tests pass you are given the freedom to make choices around sustainability, and ease gathering the material when one compares them to each other.

A series of tests made in Groot Marico. All these tests passed and although the red earth was most attractive it was decided to go with the brown earth as the red earth was further away and good for agriculture. The red earth was however used in the final plaster coat where the quantities are very small and not in the walls themselves. When a number of tests pass you are given the freedom to make choices around sustainability, and ease gathering the material when one compares them to each other.

In conclusion, often when doing tests with different earths you will find that a number of your samples will pass both compressive and tensile test. This allows you the freedom to make choices affecting sustainability or aesthetics; such as how far the material has to travel, how easy is it to gather the material and what environmental damage is being done. Remember that you are not looking for the strongest sample but rather the one that makes the most sense after it has passed the tests. Strong enough is strong enough.

In my next blog post I will look at plastering of a building where the walls are able to resist the erosion of rain and the beauty of the material shines through.

https://www.naturalbuildingcollective.com

Getting a feel for Light Earth

by Peter McIntosh

What I find exciting about natural building is that there are as many ways of using available resources as there are cultures around the world. No absolutes in terms of technique, consistency, design and use of materials exist. People approach similar decisions based on their physicality, life experience and imagination. It is always interesting to me to observe how people I teach and work with approach the material and I try not to prescribe my methods of doing things on people before giving them a chance to display their natural ability or cultural diversity. The world will be a poorer place if natural building became as regimented as the conventional building industry can be. Natural building is not a one size fits all scenario. It can’t be as the materials always vary depending on what is at hand, from rock to wood or a multitude of earths. What works here may not work there because the earth changes or the type of timber in your area is different and has different uses. What this affords us, is to become more engaged with the material and not reliant on books and building codes. There is what works and what does not, and a world in-between.

I have discovered for myself a range of techniques that work and have come to understand that technique is as important as knowledge. Little things become as important as the big things. Just how you apply a plaster coat is as important as the recipe for the mix. A material may not work in a particular way, but if you change the technique, add more or less water, put the material under pressure or just simply allow it to breathe you may have success. When I feel ready to abandon an idea that I thought might work, I find myself wondering what I am missing, because you can be sure that others with the same materials have found a way.

Combining the same materials in different ways has different outcomes in terms of structural ability and how they perform thermally. Adding just a little straw to a mud-brick will double its insulating ability and increase its tensile strength. That is not to say you want the material to become more insulating; you may want it to be a heat-sink, to radiate energy or simply just lighten the material up.

A good example of a material that offers both good insulation and a solid feel, while not being so heavy, is a mixture of straw and clay. Or, what I call Light Earth. This technique uses a common practice of placing the material in a simple brick mould and has many other uses too, from insulation in roofs to the walls themselves. It can be shuttered in situ or simply stuffed into spaces, made into boards for the ceiling or bricks.

One method of making Light Earth that I have found particularly easy is to do is to make a circle out of straw bales and lining it with plastic to form a dam.

1_Building a dam

The dam is filled with water about a quarter of the way, after which you can begin adding clay.

There is no exact recipe and a little experimentation is required. The more clay you add the thicker the ‘soup’ will become and the denser the resulting bricks. The dryer the clay is when you add it the better because it then dissolves quicker when added to water. Powering the mixer with loads of feet works best and I have a hard time stopping folks from having a clay bath during courses. Once all the clay has dissolved it’s time to add the straw. A whole straw bale is mixed in using the same method, although this stage of the recipe requires a little more effort.

2_Mixing the clay soup

Once all the straw is thoroughly coated with clay it is removed in heaps and placed on the side of the dam to drain back in any excess liquid. The mixture looks like a bunch of wet straw and not a heap of mud.

3_Extracting the material

This wet straw is then pushed into a mould with care taken to avoid layering. If the block is to be used as a structural element, for example a wall, the soup needs to be more dense so that all the gaps between the straw are filled with clay, otherwise its fine to have some gaps. Scoop any excess clay off of the top and return it to the dam.

The block moulds may be any size and can be as thin as 50 mm and one meter square if they are to be used for making a ceiling, just as you would use with conventional materials. The blocks below are 300 mm by 300 mm and 170 mm deep. A huge advantage is that Light Earth blocks are less than half the weight of a traditional mud brick and with the added advantage of all that insulation. Of course, the weight and thermal conductivity will depend on the amount of clay you added in the first place. As a rule of thumb the material approaches the insulating ability of a straw bale wall when it is 200mm thick.

4_Material in brick mould

Keep adding straw till the clay soup is used up.

These blocks are practically indestructible and survive repeated dropping with no effect. They do however take longer to dry in the sun than a mud brick and a good run of clear sky is essential. They take around 3 days to dry sufficiently before they can be turned on their side to speed up drying, depending on the weather. After about a week they can be stacked with gaps in-between the bricks to finish the process off and covered while stored to protect against the rain.

To conclude, Light Earth is a very versatile material with so many applications just dying to be tried and it’s a load of fun to make. I wonder what would happen if you threw a few kids into the mix as well?

Photos 1, 2 and 4 were taken during a Natural Building Course at Berg-en-dal, which Peter McIntosh co-facilitated with Neil Smith.

Photo 3 was taken at the Tara Rokpa Centre in Groot Marico, a Buddhist retreat where Peter was involved in the building along with architect Paul Marais.

For more information on the courses that Peter McIntosh is involved with please visit our Events page.

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