Bristol Green House Earthbags

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BAG YOURSELF A WALL
Leave the concrete blocks in the builders yard

If you have ever built a wall with concrete blocks you'll know you have to be very precise, first with the foundations, then with every course, making sure it is plum, true and straight in three dimensions.

Next time you need a wall in your garden, try using earthbags instead.

Fill the bag with a 20 to 1 mix of soil and cement, plonk it down, then jump on it until satisfied. Aaah, that's what I call precision.
I found the method and recipe for my humble wall on Sharing Sustainable Solutions. Their recipe is 20:1, in my caution we used 10:1.
They suggested that the bags could be finished with a kind of paper mache of hessian sacking dipped in a thick and runny cement mix. (see left)

1 part cement
3 parts sand
plus clay slip added until mix is gloopy but not too runny.

As I had some lime render left over (roughly 1 lime to 3 sand) I mixed this with the cement at a 3 to 1 ratio.

This will hopefully make this coating more flexible and less prone to cracking.

We tried using the hessian and it just didn't work as the cement was so heavy that the material wouldn't stick to the wall. Instead we just smeared the mix on the surface of the bags by hand in two coats. It seems to have worked so far.

EARTHBAG DOWNSIDES

I found a couple of problems with this method for building a low wall:
1. You must do the cement coating soon after completion otherwise the hessian sacks degrade and the earth starts to spill out.
2. The contents is prone to shrink within the outer shell meaning that, for example, standing on it can crack the outer shell. I ended up doing extensive repairs and making the top layer about an inch thick in cement to make it strong.


Here are some projects and images I found online to inspire thoughts of more elaborate earthbag projects. I recently met someone buiding houses in Tanzania using this method but using plastic bags with barbed wire to hold layers together.
Picture:US National Park Service.

Picture: Green Home Building.