Forgot to do this blog this summer. I set myself a goal to build and earth oven in the back garden. I have been thinking about it for a while and when they found the remains of the oldest in the UK under where we were going to build the National Trust Penrhyn Castle biomass system it sort of sealed it.
The base is made of free recycled concrete kerb stones thanks to Gwynedd Council (they were re doing a cycle path near the house and I asked if I could have them). the void in the base is filled with broken kerb and broken bricks topped off with 6″ of sand. A base of thermal bricks I found and then the oven was built over 10 days in three layers of mud, gravel, sand, straw and two types of manure!
Thanks to ‘Building with Cob’ book for leading me through the method and the measurements. Getting the door aperture right in relation to the internal void is key. (the door has to be 61% of the height of the inside of the dome) building a ‘former’ out of sand and then covering in wet news paper for the first layer to take with no straw (thermal layer)
Its was a good few days of work (The earth, sand and straw was mixed with a tarpaulin). The whole thing was more or less free except for the thermometer and some borrowed bits (£3.50 for the thermometer). What I’d do differently next time?More straw in the final finishing layer to stop the surface cracks.