We need your help with our crowdfunding campaign

We’ve launched a crowdfunding campaign because we really need your help to finish building the edu-centre in Delft so carers from informal crèches can get training in early childhood development.

We are busy building a passive solar, earth sheltered building out of tyres, cob, compressed earth bricks and glass bottles at the Delft Early Childhood Development (ECD) centre. But, we need your help to finish building it. The building will be an edu-centre so carers from informal crèches can get training in early childhood development.  

Please consider making a contribution to the campaign or spreading the word to people you know.

Following our involvement with building the Delft Early Childhood Development centre with natural and sustainable building materials we saw the space and need for an adult training centre there so that, amongst other things, carers from informal crèches in Delft and surrounding areas can receive training in early childhood development.

If you’ve ever been to a township you’ve seen how many children under the age of seven are often milling about, quietly entertaining themselves. They are starting their young lives at a distinct disadvantage as they will start primary school at age seven without any educational preparation. This is disastrous for these children and the future of our country. In the Cape Town area there are a staggering 18 000 children up to the age of 7 years old who do not attend an edu-care (according to local authority figures). Strong, inspiring and tenacious women (and occasionally men as well) qualify themselves as ECD teachers and operate an ECD from informal structures.

Visit Thundafund to make your contribution!

It has been widely accepted that the first 1000 days in a child’s life is critical to their, as well as society-at-large’s health and wellbeing. During this period, children’s brains can form 1,000 neural connections every second and these connections are the building blocks of their future. But, we need your help to complete the building…

What we have achieved to so far:

  • Peter McIntosh has raised R120 000 from The Sophia foundation towards materials and has donated three months of his time towards the success of the project.
  • We have provided employment for eight members of the local community during the building process.
  • We have provided a month-long training sustainable building course including for architecture students of CPUT. The course was presented in collaboration with Guy Williams on behalf of international NGO Long Way Home from Guatemala.
  • We have also used provided other learning opportunities for volunteers, architecture interns.

We need to get from here:

We are this close to finishing

We are very close to finishing the building

To here:

The end-goal

This is what we’re aiming for and with your help can achieve

How we’ll use your contribution:

With your help we can complete this building… Your contribution will go towards completing the following activities:

  • Planning gum pole purloins to level to install roof sheets
  • Installing IBR roof sheets
  • Complete last two sections of ring beam (shutter/form and pour concrete)
  • Source and make over 2000 more bottle bricks
  • Install bottle bricks in cob above ring beam
  • Cob scratch plaster coat, form coat and final lime plaster coat internally
  • Form and final plaster coat on internal and external bottle walls
  • Level and stamp floor
  • Gravel, newspaper, cob and compressed earth brick floor layers
  • Final layer on floor
  • External plaster finishes on tyre walls and ringbeams
  • Final touches on tyre retaining wall and earth berm
  • Front level ramp and paving threshold
  • Painting fibre board on door-front

With your support we are making a difference… Please consider making a contribution to the campaign or spreading the word. Thank you! 

https://www.naturalbuildingcollective.com

Q&A with Paul Marais, award-winning architect specializing in rammed earth

We catch up with Paul Marais about his award-winning off grid, rammed earth house in Maun, Botswana.

First off, congratulations on winning the Afrisam-SAIA Award for Sustainable Architecture + Innovation for Sustainable Product/Technology for your design of the rammed earth Otto cottage in Maun, Botswana. 

Thank you, I am very pleased for recognition of this off grid, rammed earth building , where I designed and built the house, energy & water systems and sewerage.

The award-winning rammed earth Otto cottage in Maun, Botswana. Designed and built by Paul Marais. Photo courtesy of Paul Marais.

The award-winning rammed earth Otto cottage in Maun, Botswana. Designed and built by Paul Marais. Photo courtesy of Paul Marais.

How did you first get involved in natural building?

I have been always interested in natural buildings and as a student studied natural building in Malawi and Zambia.  I have travelled a lot in remote Africa and have an interest in indigenous architecture which is both material and energy efficient.  Continue reading

https://www.naturalbuildingcollective.com

Guest post: Rammed earth on the rise

Rammed earth construction in South Africa has generally been stigmatised as a substandard and primitive building construction method reserved ‘for the poor’. Yet it is now gaining popularity for community social projects, as well as among wealthier clients.

By Mary Anne Constable

This post first appeared on Earthworks Magazine in April 2016. We are re-posting it here with the permission of  Young Africa Publishing and author Mary-Anne Constable.

Rammed earth in Botswana

House Freeman is cool in the hot Botswana desert thanks to an evaporative cooling system, which draws air over solar powered sprinklers, a living roof and thick, thermally efficient walls. The shuttering was reused in, for example, the roof, so nothing was wasted.

Of more than twenty different types of earth construction techniques, rammed earth has been lauded for its durability, sophisticated environmental performance and striking earthen beauty.

Rammed earth construction in South Africa has generally been stigmatised as a substandard and primitive building construction method reserved ‘for the poor’. Yet it is now gaining popularity for community social projects, as well as among wealthier clients. Although a building standard is yet to be formalised in South Africa, the rammed earth industry is established in many African countries, Europe, United States and Australia. This means plenty of expertise and established international building standards already exist and this construction method is now far removed from its primitive roots.

Continue reading

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

The dynamic qualities of African Vernacular Architecture

In this guest post by Jon Sojkowski, he chronicles common misperceptions of African vernacular architecture and how it is being abandoned for the status that comes with living in conventional Western style buildings. He asks whether these modern materials are truly better than the vernacular options.

By Jon Sojkowski

African vernacular architecture is a subject that has had very little attention. The lack of documentation and available data on the internet has led to a severe misunderstanding of a type of architecture that a large percentage of the population in Africa living in on a daily basis. The lack of data has led to negative perceptions regarding African vernacular architecture, mainly that it is temporary, primitive or for the poor. Most people, when they think of a mud hut, get an image of a dilapidated mud structure which is quite small and has a thatch roof. Sadly, this perception exists both inside and outside the African continent, but it is simply not the truth. Continue reading

https://www.naturalbuildingcollective.com

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

Mud house design competition

Reinventing the African Mud Hut Together

Nka Foundation invites entries for Mud House Design 2014, an international architecture competition open to recent graduates and students of architecture, design and others from around the world who think earth architecture can be beautiful.

Registration and submission of entries run from March 15, 2014 until August 31, 2014.

The challenge is to design a single-family unit of about 30 x 40 feet on a plot of 60 x 60 feet to be built by maximum use of earth and local labor in the Ashanti Region of Ghana. The client of your design is the middle-income family in any township of your choice in the Ashanti Region. Total costs of constructing the design entry must not exceed $6,000; land value is excluded from this price point. The entry should serve as an example to the local people that mud architecture can be beautiful and durable.

What is the design problem? The cause is this: in Ghana, as in other countries in West Africa, stereotypes about buildings made of earth persist because of poor construction. Earth architecture is fast giving way to modern dwellings made of cement blocks and other modern materials that are not simply expensive but thermally and acoustically problematic. From the cities to the low-income villages, use of concrete – despite its dependence on imported resources – is considered indispensable for building. The rising cost of the modern building materials manufactured from imported resources makes it very difficult for low-income families to become homeowners. Yet an excellent, cheap and local alternative called laterite, red earth, is available everywhere in Ghana.

Contact: info@nkafoundation.org

Read Disclaimer

 

 

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

Understanding Earth: The beginnings of a Natural Builder

By Peter McIntosh

One of the challenges of working with earth is that no two sites are the same. The recipes one learns on one site may not work on another, because the earths’ found there are composed differently. Most earth building relies on a mix of sand and clay, which may be present in a single earth or need to be blended together.

Sand has a particular particle size and is like a rock only smaller. You go from boulders to rocks to stones to gravel to sand to silt, or something like that. Each is a smaller representation of the one before it and just like you get many sizes of rock so you get a range of sand size. Sand particles range in size between 2mm and 0.0625mm which is a huge deviation.

The shape of sand in an ideal world should be shattered rather than rounded, such as beach sand. River sand is considered better because it tends to be more fractured so the sand particles do not slip past each other but rather build bridges and lock in together.

Ideally you also want the sand to have a range of particle sizes and not just lumped on the large side, 2mm or the small 0.06mm. This is because when the larger sand particles are packed together you will have spaces in-between and you want those gaps closed with smaller sand particles. Of course as you look closer you will see that there are spaces in-between the smaller particles and it really is like a fractal. The next range down is silt and ranges between 0.06 mm to 0.0039 mm, this particle would be able to close those gaps and so you go. So with sand you are looking for two things primarily, a shattered particle and a good distribution of particle sizes.

Clay is the magic that does the binding in earth building. Clay is completely different to what has been mentioned above except that there is some relation to particle size with silt. If you went to the beach and made a sand castle and then when it was dry a little pressure would flatten it, especially with those rounded particles. Do the same with clay and once it is dry it is immensely strong. This is because clay is not just a smaller sand particle but rather a flat platelet that is held together by electrostatic force. It works in a similar fashion to a drop of water between two pieces of glass, you can slide them apart but you can’t pull them apart. The trick with clay is to work the material until the particles are lined up to allow the electrostatic forces to work. There is always enough humidity in the air and retained in the clay to allow this process to continue, even in very dry conditions. Clay and silt are often found together in the same deposits and are hard to tell apart if they are mixed together. Mostly what is termed as a clay earth is a mixture with silt. I consider 60% a reasonable clay content . Clays also all behave differently. Some clays swell considerably when water is added and are great for the sealing of dams and the like but no good for building with cob or mud/adobe brick, as this leads to cracking in the drying process. Really fine clays also tend to be brittle, such as Kaolin, a fine white clay. So with clay you are looking for a nice high percentage with as little silt as possible, not too fine and one that does not swell to the point of compromising the strength of the material with excessive cracking once dry.

Now to create a building material both sand and clay are blended together, to get the benefits of the structure of the sand with the binding properties of clay. Basically you just want to add enough clay to coat the sand particles and close the last of the gaps left between them and allow the electrostatic force to hold it all together. You certainly do not want silt as that is competing for the space between the sand particles and is just where you want the clay to be. At around 18% there would be just enough clay to do the job. If there is silt present with the addition of 18% clay you would begin to force the sand particles apart and you would have a more brittle material, as the material is strongest when the sand acts as a bridge over each other, locking together.

But that’s the theory, in reality you are dealing with what is available and that is always going to be less than perfect. Your sand may have only large and small particles and nothing in between or any number of permutations, depending on how nature left its deposits. Your clay may be a mixed bag of various amounts of silt and swell in a less than perfect manner. So what you are looking for is not the ideal, that does not exist, but rather something that is suitable and strong enough for your needs.

Different methods can help with how the material behaves so choice of approach is important. Blending and lining up of the material can be done in essentially two ways both have their benefits and drawbacks. The first is to add water and mix the material until well blended to achieve a good lining up of the particles. Different methods allow for different quantities of water however the addition of too much water can lead to avoidable cracking or a material with less compressive strength. Cob is often the standard most people refer to and also has some added straw (straw adds to the insulation value and tensile strength of the material) The cob mix needs to be stiff enough to resist slumping when placed on a wall to the height of 300 to 500 mm. One of the benefits of using water is that different earth can be easily blended and straw can be added, a drawback may be that if the clay is aggressive or of a high overall percentage it could lead to cracking and a weakening of the material.

Adding clay to the sand on a tarp

Adding clay to the sand on a tarp

Add some water

Add some water

 

Mix cob with your feet and add some straw

Mix cob with your feet and add some straw

Stitching cob onto a wall

Stitching cob onto a wall

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The second method of lining up the particles is to put the material under pressure and not to add water beyond just slightly damp. The material can be stamped such as for rammed-earth or compressed such as with a compressed earth block. A benefit could be that as you are not adding water there will be less cracking even if the clay content is high and a drawback is that earths are not easily mixed together without water unless you have other machinery so a single earth is often used and the addition of straw is not possible.

Add your single earth into the compressed earth brick machine

Add your single earth into the compressed earth brick machine

Put the earth under pressure

Put the earth under pressure

Out pops a brick

Out pops a brick

Building with CEBs

Building with CEBs

Understanding how earth behaves is key to choosing a method of approach that supports the materials you have on hand.

In my next blog post I will talk about the qualities of earth what it means to say that a material is strong enough and how it performs (compressive and tensile strength, insulation and thermal mass) and how to test for these properties.

 

If you’re interested to learn how to put the theory of earth into practice, learn more about our natural building courses.

See Disclaimer

Previous posts by Peter McIntosh:

Getting a feel for Light Earth

You might also enjoy: Using natural materials: a comparison, by Malcolm Worby

https://www.naturalbuildingcollective.com

Using natural materials: A comparison

by Malcolm Worby

Using natural materials for construction of dwellings and community buildings, is the oldest method of building since humans moved away from caves. In fact, more people in the world live in houses built of natural materials, than any other type of building material. It is therefore the most common method of building in the world.
There are many different types of natural building materials, and to describe and go into detail about each one would only serve to confuse many who are unfamiliar with natural building practices, as some are only applicable to certain areas of the world. So, in order to keep things simple, the more popular, and commonly known and used types, are outlined below, describing the basic methods of building with the material, along with its advantages and disadvantages. This is by no means meant to be comprehensive, and is intended solely to explain the basics to those who are unfamiliar with the different types of building and material. There is of course far more detail, and also other options of how to build than is outlined below, and it is hoped that anyone who having read this information, and is interested in pursuing building using natural materials will seek a professional to assist them to make the right choices.

ADOBE (MUD BRICK)
Adobe bricks comprise of a mixture of clay, coarse sand, fine sand, silt, and water, (the ideal clay content is no more than 20% of the mixture) which is placed in a form made to the size of the bricks required, and then removed to allow the bricks to bake in the sun until hard. A binder such as straw is added only if the clay content is low. The dried bricks are built on a solid foundation, ideally stone, built to a minimum of 200mm above ground level, which also acts as a ‘Damp Proof Course’ as it raises the adobe bricks wall from absorbing moisture from the ground. A similar clay-sand-water mix as used to make the bricks is used as mortar between the adobe bricks. Fairly large roof overhangs (600mm minimum) help prevent the walls being eroded over time, and on the north wall it helps keep the building cool in the summer. Usually a 2-coat earthen or lime plaster is applied as a final finish. Adobe wall structures lend themselves to having load-bearing walls, however, a wood or concrete ‘ring beam’ is recommended to support the roof structure.
The soil for making adobe bricks is usually of local material, and ideally from the property itself. This therefore makes adobe one of the most affordable building technologies, and is often completed without the use of engineers or architects, hence the term ‘non-engineered construction’. The walls are usually a minimum of 250mm thick for a single storey and 600mm double-brick thick for added thermal mass, and for two-storeys. Ideal areas for building with adobe would be temperate climates with hot and cold seasonal swings, cold climates, and hot dry climates which fully utilise the thick thermal mass for heat storage in winter, and for cooling during the summer. In hot and humid climates, narrower thickness walls could be used, providing sufficient roof overhang is provided for shade.

Advantages:
• High thermal mass is very energy-efficient in both summer and winter, and ideal for passive solar heating and cooling. Indoor temperatures vary only about 5 degrees between summer and winter (17-22 degrees), making it naturally cool in summer and warm in winter.
• Environmentally friendly: Low carbon footprint and embodied energy
• Ideal material for owner builders and unskilled labour
• Relatively inexpensive for a long lasting building
• Lends itself to creative and free-form walls
• Rondavel (round) type Adobe buildings are capable of withstanding seismic activity
• Fireproof
• Excellent sound insulation
• Can easily be built up to 3 stories
• Can be recycled
• Approved by many local building departments.

Disadvantages:
• Fairly labour intensive
• Obtaining a bond from lending institutions is extremely difficult
• Adobe cannot be laid during very wet or freezing weather
• Insects, notably termites and small rodents can burrow into the walls weakening them. The use of dung in the mud mix, and lime plaster can negate this problem

COB
Cob, like adobe, is also comprised of a mixture of clay, coarse sand, fine sand, silt, and water; it also uses a binder of fibrous or organic material such as straw, or dung. The cob once mixed, can either be used ‘as is’ and installed in ‘lifts’ of about 600mm, or can be rolled into balls about 200mm in diameter. The building is a process of laying the straw-clay mixture or balls in layers on top of the foundation walls, which are built ideally with stone, to a minimum of 200mm above ground level. The walls start wide at the base (600mm+) and taper in as one builds up. Each layer of cob must be allowed to dry before laying the next. As with adobe, large roof overhangs (600mm minimum) help prevent the walls being eroded over time, and on the north wall it helps keep the building cool in the summer. Cob wall structures, due to their width, lend themselves to having load bearing walls, however, a wood or concrete ‘ring beam’ is recommended to support the roof structure. Usually a 2-coat earthen or lime plaster is applied as a final finish. The soil for making cob and cob bricks is usually of local material, and ideally from the property itself. Therefore cob is also one of the most affordable types of building material, and can be built often without the use of engineers or architects, as ‘non-engineered construction’. Ideal areas for building with cob would be temperate climates with hot and cold seasonal swings, cold climates, and hot dry climates which fully utilise the thick thermal mass for heat storage in winter, and for cooling during the summer. In hot and humid climates, narrower thickness walls could be used, providing sufficient roof overhang is provided for shade.

Advantages:
• High thermal mass is very energy-efficient in both summer and winter, and ideal for passive solar heating and cooling. Indoor temperatures vary only about 5 degrees between summer and winter (17-22 degrees), making it naturally cool in summer and warm in winter.
• Environmentally friendly: Low carbon footprint and embodied energy
• Relatively easy to build for owner builders and unskilled labour
• Relatively inexpensive for a long lasting building
• Lends itself to free-form walls
• Excellent sound insulation
• Cob buildings are capable of withstanding seismic activity, but must have a ring beam.
• Fireproof
• Can easily be built up to 3 stories
• Cob can be easily recycled

Disadvantages:
• Labour intensive
• Relatively slow to build
• Obtaining a bond from a lending institution is very difficult.
• Cob walls cannot be laid during wet or freezing weather
• Insects, notably termites and small rodents can burrow into the walls weakening them. The use of dung in the mud mix, and lime plaster can negate this problem

RAMMED EARTH
Rammed Earth construction is done by using a mixture of sand, gravel, clay (the proportions depend on the available soil), and water. The mixture is placed into formwork made of plywood supported by steel frames (or similar), placed on top of the foundation wall. The amount of mixture placed in a form at a time, known as a ‘lift’, is typically about 150mm deep, which is then compacted either manually, or by a pneumatic backfill tamper. This process is repeated until the desired wall height is reached. Door and window openings are created by using formwork, with lintels placed on top of the forms prior to compacting. The final result is a sculpted earth wall of exceptional strength. A stabiliser, preferably lime, but cement can be used, can be added prior to mixing, and is typically between 5% -13% of the mixture. Note: If cement is added as a stabiliser, a rammed earth wall 300mm thick, will have more cement content than a 115mm wide concrete block wall, and therefore the carbon footprint and the embodied energy is increased dramatically. For more creative builders, Rammed Earth offers the opportunity to mix colours of soil and when the lifts are done in different colours, it provides ‘stratification’ in the walls. This process when sealed with beeswax or similar, provides a beautiful finish with minimal maintenance. The thick earth wall is structurally very sound, but it is recommended that a wood or concrete ring beam be installed at the top of the walls. Ideal areas for building with rammed earth would be temperate climates with hot and cold seasonal swings, cold climates, and hot dry climates which fully utilise the thick thermal mass for heat storage in winter, and for cooling during the summer. In hot climates, it is essential that the walls are shaded at all times.

Advantages:
• Low carbon footprint and embodied energy.
• The thermal mass is ideal for passive solar heating and cooling.
• Rammed earth walls are extremely strong
• Excellent sound insulation
• Fire proof
• Insects and rodents are not a problem
• Does not need to be plastered
• Can withstand seismic activity providing it has a concrete ring beam.

Disadvantages:
• Rammed earth walls are very labour intensive.
• Building the walls is a slow and precise process.
• The formwork adds considerable cost.
• Obtaining a bond from a lending institution is very difficult.
• The walls cannot be built during wet or freezing weather
• Difficult to recycle

SANDBAG
Sandbag construction consists of lightweight plastic bags filled with sand or other earth mixes. Ideally the soil or mix is locally available on site. Typically sandbag construction utilises the pillar and beam type of structural framework construction, whereby the full bags are used as ‘in-fill’ by laying in courses, on a foundation wall, between the pillars. If pillar and beam construction is not used, the building will need to have curved walls to create added strength. Once the walls are completed, typically chicken-wire is then attached to the sandbags, which will allow the walls to be plastered, ideally with lime plaster. Sandbag walls are relatively quick to build, and due to the pillar and beam framework, they are also strong, and relatively inexpensive. Sandbagging requires very little water especially compared to adobe, cob, or rammed earth, which can be an important factor in some areas. Sandbag walls are also a viable option for constructing temporary buildings, as the materials are mostly reusable. The thick walls offer a good thermal mass which helps regulate the interior temperature of the building during both the summer and winter months. Ideal areas for building with sandbags would be temperate climates with hot and cold seasonal swings, cold climates, and hot dry climates.

Advantages:
• Relatively low carbon footprint and embodied energy.
• Sandbags can be reused or recycled
• Strong structures are erected quickly using pillar and beam construction with sandbag ‘infill’
• Minimal water needed for construction.
• Good thermal mass for regulating internal temperatures
• Excellent sound insulation.
• In rural areas, ‘Mealie’ bags can be collected and recycled as sandbags.
• Services can easily be added during the construction phase

Disadvantages:
• Labour intensive
• Care must be taken to prevent water penetrating through to the sandbags
• Sandbags are often made of plastic and are imported from China, which increases its environmental footprint, and embodied energy. Locally made bags are available, but are more expensive.
• Pillar and beam technology using steel, cement blocks, and wood from non-sustainable forests, are not environmentally-friendly
• Walls must be plastered.
• Obtaining a bond from a lending institution is very difficult.

STRAW BALE
The straw bales used for building must be of grain stalks (oats, barley, wheat, etc), as opposed to hay bales, which are made from grasses. The use of straw bales as a building material is very environmentally-friendly, as the straw if not baled, is typically burned by the famers after harvesting, creating tonnes of air pollution. Building with straw bales either utilises the pillar (or post) and beam type of construction, with the straw bales used as ‘infill’, or the straw bales built as a load-bearing wall. In the load-bearing wall method, a wood roof or top plate is installed covering the full width of the top of the wall, which in turn is attached to the foundation, typically with wire straps, on approximately 1200 centres. The top plate acts not only as a bearing plate, but also as a ring beam, distributing the roof load evenly along the walls. Window and door openings will need to be structurally framed in with wood in both methods. The walls when completed, and the roof is installed, are typically covered with chicken wire, and then plastered with either mud or lime plaster on the exterior, and mud, lime, or gypsum plaster on the interior. It is recommended that there is a sufficient roof overhang to help prevent water saturation during heavy rains.
Straw bale building, due to its high insulating value, is most beneficial in hot, dry desert climates, high desert climates with large daily temperature swings, cold climates, and temperate climates which have relatively hot summers, and cold winters.

Advantages:
• Energy efficient, as straw bales have a very high insulation value.
• Straw bales are produced from a waste product that is bio-degradeable.
• Can be built using unskilled or semi-skilled labour.
• Not as labour intensive as other natural building methods.
• Structurally strong
• Excellent sound insulation
• Relatively inexpensive material to purchase

Disadvantages:
• Straw bale walls are susceptible to mould and deterioration unless protected from moisture, and allowed to ‘breathe’.
• No thermal mass for passive solar heating and/or cooling
• Transportation increases the embodied energy/carbon footprint, and also the cost, unless building on a farm growing cereal crops.

As published on Enviropaedia under the title Green Building: Using natural materials

Disclaimer

Malcolm WorbyMalcolm Worby studied at Bristol Polytechnic in the UK and has had his own award-winning architectural design firm ‘Malcolm Worby Designs’ for over 30 years specialising in natural, sustainable, and environmentally friendly building. He now specialises in providing consulting services for natural and sustainable building projects, including mud brick (adobe), straw bale, sand and earth bag design and building, passive and active solar heating and cooling, photovoltaic (PV), grey water recycling, rainwater harvesting, and composting toilets. He has designed buildings in various parts of the world including the USA, UK, South Africa, Mexico, and the Netherlands, and has worked on low income affordable community-build projects in South Africa, Malawi, Mozambique, South Sudan, Uganda, Zambia through his Non-Profit Organisation ‘Homeless And Poor People’s Initiative’ (HAPPI).

https://www.naturalbuildingcollective.com