… and 2014 is no different.
It is with pride and joy that we look back on the successes and new connections made during 2014.
We launched our blog in March and have had over 5000 visits from people in 98 countries! The blog contributions included knowledge shared by our expert natural builder Peter McIntosh, to fly-on-the-wall takes of life as an architect and educator interested in building naturally and sustainably by Hermie Delport, personal lessons learned by owner-builder Laurie Simpson, and Amanda de Gouveia’s contributions as social development researcher at Qala Phelang Tala, a grassroots community upliftment and alternative building project focused on vulnerable communities in Bloemfontein. Other contributors included heritage consultant Lesley Freedman who about using indigenous earthen architectural knowledge, and green architect Malcolm Worby shared his thoughts on a comparison between natural materials.
Peter wrote a special piece for The Green Times, South Africa’s Green News Portal, on the relationship between building naturally and building sustainably; and our most popular posts this year on the blog has been his three part series on Understanding Earth, how to test earth, and how to make the appropriate decision with regard to plaster and mortar mixes.
Peter McIntosh facilitated three courses this past year: two CPD accredited courses at Magic Mountains in Barrydale, and one 6 day Natural Building: Materials and techniques course at Khula Dhamma in the Eastern Cape. All-in-all 33 people attended these three courses and got to do the mud dance and experience the art of natural building. Hopefully, that translates to at least 33 more natural buildings in South Africa!
Khula Dhamma reckons the course is a winner:
‘It’s hard work but huge amounts of fun, highly therapeutic and more rewarding than one could ever imagine. With the different techniques and materials and their thousands of capabilities, you are literally only limited by your own imagination and there is something so beautiful about that!’.. Read more.
If you want to see what other participants had to say about the courses please visit our updated Testimonials page. Or if you’re interested to see photos of the courses, you can either go to our albums on Facebook, or visit the Gallery page on the blog. Thanks to everyone who has liked, commented on, and shared our posts and events on Facebook! Our page has continued to grow, and we now have over 1200 likes, all thanks to you. If you’ve attended one of our courses, please note that we’ve now added the option to review us on Facebook.
Finally, Peter McIntosh has been part of an amazing project at the Lebone Village Arts and Culture Centre in Bloemfontein as one of the Mentors4Change. This collaboration with Qala Phelang Tala (Start Living Green) started on Mandela day, July 18th when Peter trained a few hundred people in the art of making mud bricks. Amanada de Gouveia wrote about the day here. Since then they have had a team consisting of volunteers and outpatients from the University of the Free State’s Occupational Therapy clinic in Rocklands location, hard at work on the Shack Replacement project. This team was also privileged to attend the course at Khula Dhamma.
In recent weeks though, the focus has shifted to the Lebone Arts and Cultural Centre and the existing above ground cistern at the local orphanage. The crew includes volunteers, outpatients from the occupational therapy centre, a crew from Guatamalan NPO Los Técnicos (arguably world experts in alternative building practices [tyres, bottles bricks etc.]), and Peter McIntosh . Here you can see the progress from day one to day nine (photos courtesy of Los Tecnicos). For more photos of the building progress, please visit their Facebook album of the project.
The project is set to continue for another week or so, and hopefully they’ll get it all done in time. A great partnership has been fostered between these three organisations and holds great promise for other projects in 2015… Watch this space!
Finally, thank you to old friends and new for a blessed 2014. We’re looking forward to continue this muddy journey in 2015 as we explore new relationships and exciting new projects, more photos, knowledge and experience in how to build naturally and sustainably, to bring you, our supporters. We’ll be publishing our course dates for 2015 early in January so do keep an eye out for that if you missed out this year.
Thanks for joining us again, and we’ll connect with you sometime, somewhere soon…
the Natural Building Collective
PS If you would like to get involved and write for us, be it a once-off, or more regular contribution, please send us an email with what you have in mind.
Plasters and mortars are by far the process that I get asked about the most, and for good reason as plasters are what protect the building from the elements and give them their beautiful finish. Understanding how the material is going to behave right the way through the process, plasters and mortars should be planned for from the beginning. Plasters that are not planned are plasters that fail and if they do the building not only looks unsightly but loses a valuable layer of protection.
As discussed in the earlier articles on understanding earth and earth testing, it is important to establish the most appropriate earth mix at the beginning of the building process. This mix quite literally informs the whole building process from the ground up to the last 3mm of plastering. The initial testing phase establishes a basic cob mix that has both sufficient compressive and tensile strength and has acceptably low cracking. It is important to have an idea of how you will approach each phase and ensure that the different materials ‘talk to one another’ to prevent excessive cracking and delamination, which are the most common failures associated with natural building. Essentially the same original mix is manipulated to be appropriate for different areas, depending on the purpose. Areas that will require the original mix to be manipulated are, amongst others, the foundations and plasters.
It is important to remember that there are as many mixes as there are building sites and what follows is just a taste of what is possible. Over the years one comes to settle on a strategy that works and begins to perfect it to prevent failure. What follows works, but is by no means the only way and is one amongst many.
Let us imagine that the mix you worked out after the testing phase was two parts clay and three parts sand, i.e. 40% clay earth and 60% rough sand, and straw. Just an aside, this formula would indicate that there is a percentage of silt present in the clay earth (often the case), otherwise the clay percentage would usually be lower.
Let’s start with a mortar mix for the foundations. Firstly you will leave straw out of the mortar mix for the foundation, as it would degrade with any moisture. Obviously the foundation should be able to resist water, so using un-stabilized mud-bricks or cob is not possible; ideally you have rock available.
Lime is often seen as the answer to stabilise mortar mixes, as it hardens over time especially when exposed to moisture. However, lime is not friendly to the environment due to the high embodied energy i.e. the energy used to create the product. Over time lime does re-absorb the gasses given off by it during its production, the energy required in this phase is considerable and may well come from a polluting source such as coal. Furthermore, lime is quarried or produced by crushing coral. Lime also makes the material more brittle and prone to cracking, even though the material gets a lot harder, compressive strength is not everything. Often, lime is considered to be better than cement, not because it is less damaging to the environment, but rather because it is naturally occurring and an ingredient of cement. So the strategy should be to minimize its use.
Earth mixes are more plastic and able to resist a certain amount of movement so care needs to be taken just where you apply the lime. However the use of lime is beneficial in foundations where the pros of lime, its hardness and resistance to moisture, are required. With the earths in our example, a mortar mix that will work with the rock foundation is 30% clay, 50% sand and 20% lime. This keeps the material as close as possible to the original mix while getting the benefits of the lime right where you need it. If you pay attention to how the rock work is done you will minimize the use of the mortar and thus minimize the use of lime.
As your house is exposed to variances in temperature and humidity, you want to prevent the materials in the walls from moving at different rates as it causes delamination and cracking, which is in my opinion, the number one reason for a natural building failing. To help prevent this you need a good mortar mix. This is an area that your mix does not need to be manipulated. Between your mud bricks it is ideal if you stick to the original mix that came directly out of the testing phase, including straw.
While some imperfections are fine in the foundations and mortar mixes, any imperfection in your plaster mix will have dire consequences for you final finish. This is mainly because there is generally no amount of acceptable cracking in the final plaster as this leaves the building vulnerable to water erosion. In a nutshell, plaster provides the final finish look and provides protection from the elements.
I have adopted a three phase approach to plastering that is well accepted and works. The first is the scratch coat, the second the form coat and lastly the final plaster coat. The scratch coat is your original cob mix applied to the mud bricks to give purchase to the subsequent layers. It includes straw and is left rough often with lots of fingertip marks.
The form coat is just what it says and creates the final shape of the building. At this stage it is best to leave out the straw as you don’t want anything protruding through your final plaster coat. The form coat is hand smoothed in such a way that the final plaster coat can go on evenly with a plastering trowel or steel float. Fine cracking is still acceptable in this phase.
Prior to the final plaster you will need to do a number of tests on top of your form coat. This is done to ensure that there are no fine cracks that will lead to erosion by water. Often cracks create wonderful patterns and you may want to leave the mix to show off its beauty but only on the inside plaster. On the outside no cracking is acceptable after the material has been polished. Usually I do about four tests to select the best mix. Based on our theoretical mix for this article the four tests may look something like this.
- First your original mix, 40% clay, 60% sand with 5 % lime =105%
- Second reduce the clay a little to reduce potential cracking 35 % clay earth, 65 % sand plus 5% lime.
- Reduce the clay some more just in case there is still cracking to 30 % clay earth, 70 % sand plus 5 % lime.
- Lastly increase the clay content over the original mix, 45% clay earth, 55% sand plus 5% lime.
As these samples are applied so thin they will dry fast so decisions can be made fairly quickly, perhaps after three days or so. You will need to choose the mix that does not crack. If it so happens that none of them do, pick the one closest to your original mix to ensure that the dreaded delamination is ruled out. If you are confident that this will not happen then choosing the mix with the highest clay content will lead to a very fine finish.
Technique is as important as information when it comes to natural building and nowhere is that more important than with the final plaster mix. The final plaster mix needs to go on evenly between 3 and 5 mm thick. The mix changes slightly to include 5 % lime, but only in these last few millimetres. The reason lime is added to this final 3mm – 5mm of the walls is to improve the resistance of the final plaster to water; the percentage is kept low so that the material does not become brittle and prone to cracking, and allows the natural plasticity of earth mixes to overcome small amounts of movement and not delaminate from the wall. There is also a reaction that takes place between the lime and clay that is complete between 5 and 7 %, which greatly increases its durability.
The final plaster mix will need to be finely sieved so that bigger particles do not protrude through the plaster and the result is smooth and even. I prefer the common kitchen flour sieve. Don’t be put off, by how long you think it would take, because you really need so little for the final plaster mix that it goes quite quickly and you can do it directly into a bucket.
Once the final plaster is applied it is polished to provide a very smooth almost fine leathery appearance, further driving the material into the wall and providing durable weather protection. A plastic tool cut from feta or ice-cream tubs work well for this final polishing stage.
Once the plastering is complete, coat the building with three coats of raw linseed oil. Mix the first two 50/50 with mineral turpentine to ensure that the linseed oil penetrates well into the plaster. Allow each layer to dry before you apply the next. Finally a coat of undiluted raw linseed oil will finish it off.
Looking at the whole process as being one thing instead of being separate little bits helps to avoid common problems. Always pay attention to the testing phase, understanding that the same mixes you use for your bricks and mortars will be reflected in your foundations and plasters.
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