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.
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.
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.
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.
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.
In this edition of the Owner-builder journey, Franz Muhl writes about a mud brick addition to his Scarborough home.
Five years ago, Peter McIntosh gave me +- 900 sun-baked mud bricks, for an extension to my house. With 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. In 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
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. Email email@example.com to book your spot!
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!
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.
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.
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.
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.
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.
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 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.
(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
– 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.
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.
– 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.
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
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.
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.