Requiring no special equipment and no special expertise, and very economical to boot, earthbagging is famous as an ‘idiot-proof’ technique, popular with first-and-only-time owner-builders the world over. Venetia Kotamraju, who moved from busy Bangalore to a farm on the Western Ghats, writes on her experiment with earthbagging. The second installment in a series of four.
The earthbagging process couldn’t be simpler in theory:
dig a foundation
fill bags with gravel to form the wall base, and then with moist mud to create the upper two-thirds of your walls; add barbed wire between each layer to knit it together
stick on a roof
plaster the walls with mud and then lime
In practice of course, it gets more complicated. So I’m going to try to describe each part of the process for the first-timer. Kaki Hunter’s Earthbag Building has been our bible for this project, and much of what is described here you can find in more detail there. There are many other books and resources out there; make sure you have a good one to hand.
Design and Planning
There is not, as far as I know, such a thing as an earthbag architect. You need to visualise, design and plan every last detail of your structure yourself. It is tempting to look at the amazing structures others have built and try to replicate those gothic arches, reciprocal roofs and stained frescoes. Three words of advice: keep it simple. Build a bench first, or a low non-load bearing wall. Progress onto a structure with openings such as a door. Save the earthbag dome, awe-inspiring as it is, for later.
Building round rather than square will also make things much easier. Round earthbag buildings need no buttressing – supports to keep the main walls standing – and are thus simpler and more solid. They also provide more square footage than a rectilinear building of the same perimeter. And there is something special about the look and feel of a round building, good energy and very primal.
All of our earthbag structures have been round. We started off with a circular low wall for the round house with openings but no doors. It came out solid but very bumpy and uneven; thankfully it’s only three feet high so that doesn’t matter. Our next attempt was a full height wall for a round bathroom with a door. We figured out level but didn’t think about plumb until we were half way up, at which point we discovered our walls had a definite lean. That destroyed one door frame, and in the end we didn’t dare balance the roof on the walls so created a free-standing roof in steel.
This year’s project is a similar circular building, with an inner radius of 10 feet and walls of 7-8 feet tall. We are though indulging our earthbag ambitions by building two arches to form windows, and we also have three doorways, one for the main entrance, one leading into the bathroom, and one just in case we decide to add on adjacent room next year.
Materials and Equipment
(Note: For costing see the final post in this series.)
We initially got a few used plastic cement/fertiliser bags – called cheelas here in Karnataka – but quickly realised that wouldn’t work as they were worn out and of different sizes. The only thing that will break these polypropylene bags down is sunlight, and most second hand ones will have had far too much of that already. You also need bags of all the same size otherwise achieving level and plumb will be virtually impossible. We now get new bags of a specific size in large quantities from Hassan.
Other materials you will need include: boulders, jelly stones, sand, barbed wire, nails, wire and plywood for the forms and attaching plates.
The boulders and jelly come from the local quarry and obviously involve blowing up hillsides. An added worry is that there have recently been elephant incidents near the quarry – I’m guessing they are now blowing up bits where the elephants live, driving them understandably into a rage. Not exactly ideal, but I haven’t been able to find an alternative. I did suggest that we use rubble from demolished houses but was told very definitely that that would not accord with vastu.
The sand comes from our local river bed, delivered by the Sullakki bad boys in their pickup trucks. As far as I can tell, the whole thing is illegal. There is no other source of sand though, so all we can do is try to minimise its use (concrete structures of course use lots and lots of sand). An alternative to sand is quarry dust, but in our area that is the same rate and involves more transportation, plus the elephant issues as above, so I’d rather support our friendly neighbourhood sand mafia.
Before beginning the bags, in addition to all the materials required, get yourself set up with all the equipment you need. For a round building, most important is a pole compass which should ensure you build level, plumb and keep to the inner radius. We didn’t make one the first time round and thus ran into huge problems. Creating a pole compass though is not as simple as it sounds.
What we have done is to:
dig a large hole, fill with cement and jelly and then set a 4 ft metal pole in it, ensuring that it is level and plumb before the cement sets…
insert inside that a slightly narrower metal pole of about 10 ft high
and finally put a horizontal pole onto that
The horizontal pole was a headache: after trying rope (not rigid so can’t check for level) and a bamboo pole (not straight itself so doomed from the start), we bought a metal pole but found that that bent downwards under its own weight. By balancing this pole though on the current earthbag course we can check for level, shifting it up for each subsequent course.
And we marked the inner and outer radius on it so that as we move it around we can ensure the bags are sitting in the right line.
Or could have had our foundations been built in a perfect circle as they should have been. As it is we have a slightly wonky circle making it much harder to get the bags in line.
We also spent a lot of time trying to figure out how to use a water level but ultimately gave up and used the spirit level mounted on the horizontal pole for level, and a second spirit level on a metal rod to check for plumb.
You will also need:
– a tamper; this is called damask here and is easy to buy
– a hammer
– wire cutters
– measuring tape
– spirit levels
– identically sized metal buckets or some other container with which to measure your mud or gravel
– gudlis; these are so much easier and more efficient than the Western spade or shovel
– a wheelbarrow is recommended by all Western earthbaggers but then the wheelbarrow is ubiquitous there (perhaps because labour is so much more expensive). We built our two structures last year without one but have now bought one, at great expense and with some difficulty – it is called ‘telu gaadi’ in Kannada and is available only in Bangalore as far as I can see. It has though been extremely useful and has enabled us to follow a completely different, and much better, process for packing the mud bags.
– and a tarpaulin or five is imperative to protect your walls from the sun (when you just have the bare plastic bags – too much sun will make them disintegrate) and the rain (when you start to plaster – fresh mud plaster will just dissolve in the rain)
It is also worth making a bag holder. We followed the suggestion in Earthbag Building (with measurements provided) for this but added an extra ring in the middle because we found that with just a top and bottom ring the bag became too fat around the belly and it was difficult to pull the stand off.
Others build bag holders out of old pieces of wood. And last year we had the most basic bag holder of all, a person. What we found though is that you needed two people to hold each bag to ensure the contents of a tipped bucket went inside properly, and it was thus fairly inefficient.
This year we have also created a basic metal slider upon which the bag being filled sits to protect it from the barbed wire below.
We are in a heavy rainfall area (100 inches a year) with high humidity but no real risk of flooding.
We thus find gravel trenches like this sufficient:
dig a trench about 1.5 ft deep and 2 ft wide
level it as far as you can
fill with large rocks (‘boulders’ they are called here) from the quarry, then fill in the gaps with sand and lots of water to help it percolate.
then add about 3 inches of large gravel (’40mm jelly’) to bring it up to the ground level
Digging the trenches is backbreakingly hard work but fairly straightforward, until you get to the levelling that is. We used a water level to try and ensure the base of the trench was level before we started adding the boulders. Then we said we would try to ensure level when we added the 40mm jelly, but when we got to that stage we decided to wait until the first course of jelly bags and so it went on. Bottom line: get your foundations level as early as possible and don’t rush this stage. If your foundations aren’t level, you are going to have big issues.
Doors and Windows
Once you’ve perfected the mix-fill-place technique, earthbagging becomes fairly easy… until you encounter an opening. Windows and doors require a lot of thought and planning, preferably before the construction gets anywhere near them. We have tried shortcuts of various types, and all have massively backfired and led to a lot of re-work. I would thus recommend that you invest the time and money planning exactly where your windows and doors will be, and their dimensions, and then create custom-made forms or frames to brace the openings as you pile up earthbags around them. We finally settled on reinforced doorframes, nailed to pieces of wood that are sandwiched in between the earthbags, which we retrofitted with some difficulty.
And if you are mad enough to attempt an arch, you definitely need to build an arch form, and also the special mould that helps shape the bags over the arch. Instructions for both are found in Earthbag Building and there’ll be more on windows and doors in the next post in this series.
As well as mud, you need some serious manpower to build an earthbag structure. You could build it alone but it would take years and be rather lonely. We hire a team of several burly men from the village, and we pitch in as much as possible, although often rather pathetically, much to the workmen’s amusement. For the plastering, we find women are much much more effective, and more chatty to work with. We usually hire a team of about four women for the plastering with maybe a man or two to mix the mud.