I made a comment on Facebook recently stating how much I love to work with cob more than any other earth building method.
Here’s a selection of techniques and my impressions which help me decide which method to use in a specific location:
We’ve built Earthbag foundations in Canada (OUR Ecovillage ), Tanzania and Cameroon. The earthbag foundations work well and are low cost in places where stone isn’t available.
At a Natural building colloquium I filled long tubes with earth. Friends from the natural building movement have built beautiful domes and other homes with this method. I believe if there’s clay in your soil, forget the bags and build freely with that clay-soil. It’s a matter of location and what’s available.
Another amazing technique producing beautiful and stunning buildings is Rammed Earth. Layers of different colors tell the story of the earth at the location. I’m talking about rammed earth free of cement here, as its being done by several builders in Europe. This way of building requires serious formwork and planning. My personal experience is limited to observation, because in my work I’ve been in locations where that formwork is very difficult (expensive) to build. As a result rammed earth shows up on the high end of building cost and in larger scale buildings.
Many cultures have built with Mud blocks (Adobe) and still do so. Here in Cameroon I see homes being constructed with a mud-block infill system, using concrete for structural support: ringbeams and to bridge large openings. Local people have experience producing these blocks and will make their own when it’s time to build a home. Making blocks doesn’t require much: water and clay-soil. Fiber isn’t so commonly used but is useful to prevent cracks and to strengthen the blocks. You need a flat area to lay out the blocks to dry in the sun- this will take about a week. Then dry storage until construction begins. Building walls with blocks requires some skill- to build a house takes some practice at masonry work. And those blocks are very heavy to lift. However, depending on seasonal patterns and workflow, this can be a great way to build an earth home.
Compressed Earth Blocks
Compressed earth blocks (CEB’s) can be made with or without cement for stabilization in various shapes and sizes. Simple mechanical block presses require at least two people to work together – mixing the clay-soil (sometimes sifted) with a little water, then filling the form and compressing with the power of a long lever. Scale it up and you’ll see machines working with hydraulics taking the hard work out, but driving up the cost . The result is a firm, even block, sometimes interlocking. We’ve just finished building our dormitory walls with CEB’s – because we had the perfect soil on site, were too late in the season for sundried blocks , and had straight walls to build. We hired a local builder to lay the blocks as they came from the press. It got the job done.
Parallel to this process our volunteers were building with cob. We created some hybrid walls with the blocks to add sculptural details and bottles. And we shaped benches and a lounge area. A layer of cob fills awkward spots in the block walls (filling around posts etc) . I watched inexperienced building volunteers mix great batches of cob, build the walls and trim them. Everybody took on designing with bottles- allowing one individual to be the overall artistic eye.
And that’s where that statement came from.
Watching people, who have never built anything, confidently building something beautiful makes my heart sing.
We’ll be moving into Earth plasters next – where sculptures get refined and block-walls disappear behind a hand-applied layer of mud. Earthen plasters can be simple sand/clay mixes applied by hand or more sophisticated ones with additions of ingredients like mica or marble dust, finished with special trowels. It’s up to the availability of materials, skills and taste, desires and budget of the owner.
Hybrid of techniques
The beauty with all of the options above is the possibility of mixing things up. We call it hybrid homes- for example walls of cob on one side and straw-bale on the other. Or adobe with inserts of cob for bottles and other sculpted elements. All tied together with beautiful natural plaster finishes.
I’m heading to Kenya this summer to create a cabin for my host Joannah in a couple of workshops. She’s already collecting beautiful things to incorporate. Dreaming her space. Clearing the site.
When participants arrive we’ll work with a selection of techniques appropriate to the location and learn about decision-making in the process. This opens up the possibility of being creative builders in collaboration with others. We’ll be supporting the first stage of a learning center for permaculture in a protected forest.
So if you are so inclined, come to Kenya this August! You will get your hands muddy and experience a different sort of safari!