Earthbag wall and cob pizza oven part one

For about the last three years I have been thinking about building a cob pizza oven and a nice curvy earthbag wall to create an entertaining area at the end of  our deck.

There is a concrete slab there that a shed used to be on and I thought I would use that as the basis of our new entertaining area.

I have built a wall from earthbags and a pizza oven from cob before in a local community garden. Now I would be able to combine the two. I get inspiration and information from the following.

A curved wall is very strong so as our house has a yin and yang theme running through it I based the design on this. A curved wall that will have a seat at each end, a preparation bench on the Pizza Oven side and a sink on the veggie garden side. This curved wall runs through into the U shaped pizza oven area and the continues along side the fence to create another bench top area and athe seat at the end. See gallery at end of post for more visual detail.

Normally earthbag walls are built using polypropylene bags or tubes but as this build is designed in my mind to be as low cost as possible we visited the local tip shops and bought a large number of queen or king size sheets and doona (duvet) covers for very little cost once we explained what they were for. The tip shops were glad to get rid of the really ugly or old sheets etc.

These were cut into strips 700mm wide and overlocked into a tube. This gave a dimension to the earthbag wall of approx 300mm deep and 50mm high each layer.

The next step was to dig foundations and lay in some plastic. This is to wrap up the first 3 or 4 layers of earthbag so that they become a stem wall and acts as a barrier to moisture wicking up the wall.

 

When I last built an earthbag wall I used clay from the community garden. This time I was going to use a pile of dirt that I had collected over time as I did other projects around the garden. Our soil has quite a lot of clay in it but some of the dirt was dried topsoil. I mixed the two when I loaded the wheelbarrow. First of all I used the dirt I had dug out of the trench.

Earthbags are filled with soil or clay or scoria, laid in position on top of two rows of barbed wire (except for the first layer, this was laid straight into the trench that I dug and lined with builders plastic). The earthbags are then tamped down flat and firm using a tamper.

Cutting the base out of a small recycled plastic bucket it became the ideal sized funnel. I used a length of elastic tied into a loop as a means of temporarily holding the funnel inside the fabric tube.

Step by step to filling recycled fabric earthbags.

  • Sew fabric tubes 700mm wide and leave turned inside out
  • Use a zip tie to fasten one end
  • Turn inside out and put funnel into open end and secure
  • Either have a helper hold the funnel or create a holder so you can use a small bucket to fill the earthbag with soil.

    using old workmate vice to hold earthbags whilst filling

    using old workmate vice to hold earthbags whilst filling

  • Make sure that the soil is a little damp. it should hold together when squeezed with your hand. Some websites and books say to add a small percentage of cement but I decided not to.
  • When earth bag has some soil in it (you need to be able to lift it!) place earthbag in position.
  • Continue filling until it is nearly full. You need enough earthbag left to be able to twist closed and tuck underneath the bag. The weight of the soil should keep it closed.
  • Tamp with tamper until firm

    tamper on right. Check for level.

    tamper on right. Check for level. Note barbed wire on red coloured earthbag. Also star pickets to keep wall vertical.

  • Check for level

A few things that made life easier.

  • Star pickets are your friend. I drove six star picket in at intervals ensuring that they were vertical. They were driven in to the correct finished height of the wall, in this case 1200mm. I made sure that the earthbags touched the star pickets and this kept the wall vertical. it is easy for it to end up out of shape if you are not careful.
  • The tamper was made from scrap steel from the tip welded together and a broom stick used for a handle bolted in. The handle broke on occasions and I just replaced it. As the wall became higher it was easy to cut the handle down to make it shorter and easier to use on the higher walls.
  • Holding down the barbed wire with bricks.  I found that I could use a brick to weigh the end down and then position the wire in one run so that I ended up with two parallel strands. Using bricks at intervals ensured that the wire stayed where I wanted it. As I laid the earthbags I would remove the bricks.
  • Lay the earthbags in a “stretcher bond” pattern.That is make sure that all joins are always overlapped. You can see this clearly in the last photo above. If you need to cut a bag short do so.
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