Tuesday, 20 January 2015

Dancing the cob stomp. Building a cob oven. Part One.

The Green Backyard
An amazing project which brings together community, art, sustainability and self-sufficiency

This past weekend we were booked onto a cob building course at the Green Backyard in Peterborough.
Before I talk about cob, a word or two about the Green Backyard. I have been there a couple of times before and really could not imagine a more welcoming place. It is a community garden right in the middle of Peterborough run along green principles, recycling, sustainability, creativity etc...
There always seem to be people popping in and something going on.

At the moment this precious project is unfortunately under threat. After 6 years of hard work, in which time their achievements have been amazing, there is a threat from the council to sell off the land to developers. Peterborough calls itself an Environmental City, so it is difficult to see how this can square up.

If you'd like to find out more, or support the GBY in their bid to buy the plot of land they sit on, please visit their website here.

So, back to the cob course. It was to be a busy weekend, starting with Blokes Baking (Shortbread and Doughnuts) on Friday evening. Another sharp frost predicted for Saturday morning meant that I was keen to get out for an hour or so with the rotavator. This is the only time I can easily turn the soil surface at this time of year.

Then we were booked on the cob building weekend from 11 a.m. followed by a dozen people coming round for the Smallholders Veg Growers Group which I was hosting in the evening.

We turned up to find that about 20 people were already there, all warmly wrapped up ready for a hard day's work (and socialising and learning).
Alan was our very expert leader for the weekend. He is based in Sherwood Forest and has spent many years working on sustainable building, green woodworking, woodland management, blacksmithing, charcoal kilning... basically, all the stuff I wish I'd got into many years ago.

Alan is well into double figures in building cob ovens. After a little background information, he led us outside where we all started demolishing an old strawberry patch. The idea was to clear away the topsoil in order to get at the clay/silt/sandy mix that is the subsoil.
This was to be our raw material for making cob.

Now that I think about it there are many meanings of the word cob. Loaves, webs, swans, nuts, corn, a sulk... All of these and more. But the sort of cob I'm talking about is the building material, made by mixing clay soil, sand and straw. It is much like the adobe walls I have seen in many tropical countries.

Today we were to be building a cob oven, but I have my mind set on using this building method to construct a new pig house and maybe as low dividing walls to divide up the chicken pen.

It's amazing how quickly 20 people can dig a big hole in the ground. It turns out this was the easy bit! Fortunately the subsoil had just the right mix of clay and sand, so we could work with what we dug, unadulterated. For the first layer of the oven there would be no straw mixed in. These fires can easily reach several hundred degrees centigrade, so the straw would not last too long and would just burn away to leave holes in the cob which would weaken it.

So we barrowed the subsoil onto a large tarpaulin, mixed in a little water and started stomping the cob dance! It's quite a simple process really, just stomping and jumping and twisting on the soil until it mixes. Roll it up and over in the tarpaulin and repeat...and repeat...and repeat...

Eventually you end up with your building material. After carefully shaping an igloo mould out of sand, we started the task of building up the first layer of the clay oven.

Alan explains to us
where the oven will sit

We gave the sand igloo
a coat of newspaper

For the future, it was maybe not the best idea to choose such a cold day for this. Shaping 'bricks' out of wet clay with your bare hands sucks the heat out of them very efficiently. My palms were caked in mud but the back of my hands was blue!

At that very moment the call went out that pizzas were now ready to be made on the rocket stove. I dipped my hands into a water butt, breaking the ice as I did so. My hands STUNG! They really STUNG! But the clay took some washing off and was I glad to find a slightly less cold bowl of water waiting over in the outdoor cooking area.
Anything hot would have tasted good right there and then, but the pizza which Sue had knocked up was especially delicious.

I retired inside for a while and took the chance to have a chat with a few of the Green Backyard regulars and to pick Alan's brains a little more. When I finally emerged, the rest of the group were just putting the finishing touches to the first clay layer.

The completed first layer,
artistically scored as a key for the next layer

It was time to bid our farewells for the day. Sue and I had really enjoyed ourselves. Hard work, fresh air, a bunch of like-minded people and learning a new skill had made for a very, very good day.

By the time we got home and sorted out the chickens, it was five o'clock. I was pleasantly shattered and had one hour to veg out before the Veg Group started arriving. More on that later.


  1. That looks to have been an interesting event. Do you think you have suitable subsoil your way? Presumably you have the typical peaty fenland soil? Where we have recently moved to at the bottom end of the fens we have very sandy soil which is quite deep. (I bought a square foot of the GBY and hope they are successful).

  2. The peat up here is very localised. We have a clay soil, quite heavy - hence the need to rotavate when frozen! I'd like a bit more sand or silt. There are small patches of more silty soil here and there. If anything, we'll have to mix sand in, but I'm hoping we'll get away with what we've got. I'm planning on doing it when we get a couple of ponds dug out.
    I'll probably run some sort of training for the smallholders group. That way I get a bit of free help and everybody gets to learn about cob!


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