Started in autum 2019, this is a new project that is slowly evolving over 2020 lock down period. We have long needed a rodent proof, frost proof structure that would act as a storage facility over the winter months to enable us to store our crops for longer. Finding a suitable place to keep apples, carrots, potatoes, jerusalem artichokes etc away from little teeth and fluctuating temperatures has been tricky, so this project is an experiment really. The idea was also made in conjunction with a desire to deepen and extend our first wildlife pond (made 16 years ago) into a possible aquaculture carp pond, which I will write about another time. When you start digging soil out - ours is sandy loam over a relatively high sandy-clay sub soil, perfect for cob making - you need somewhere to put it all or else it just soon becomes a nettley mountain! Hence a new structure made of cob, which with its thick insulating walls might become a winter 'cellar' for us. I say might because it is, like all my projects, an ongoing experiment.
First I chose a site that is shaded by a hedge and next door building to reduce heat gain, and is pretty close the the source of the clay to reduce effort transporting down the garden!
I built a base from second hand car tyres(sourced for free from local garage) filled with gravel and then filled inside the tyre walls with gravel to give a 20cm depth of compacted gravel to help prevent rodents coming up. This was overlaid with several layers of old aviary wire which I had procurred several years ago when my mother dismantled her aviaries. I overlapped the gaps in the wire to try and again narrow rodent access. If this doesnt work I may have to cement a layer over this, but I'm hoping to avoid that if at all possible.
I then bridged the gaps between tyres with eco grade OSB smartply, left over from building the roundhouse, in order to give support to cob walls at these points where the tyres meet. You want to avoid cob from ever touching the ground and also you don't want the tyres sticking out further that the walls as this will catch rainwater and feed it back to the cob. The cob walls will evntually be rendered or lime washed, and water needs to be able to drip off at the base and not feed back into the base of the wall.
I then had Stroud PDC group round in October 2019 and they spent a happy afternoon making cob with clay, sand and straw and starting to build the walls up.There was some strange shapes created which I did have to afterwards knock back into alignment, but cob is very forgiving while it is still drying!
The two fence posts are set into the ground with postcrete and they take the door frame eventually. The door will be quite narrow to reduce temperature. Old chicken waire is wrapped around to eanble the cob to take to the wood better, but the exposed wire will eventualy be cut away so a door can be fitted.
In the internal corners I am setting corner shelve brackets into the wall as we build up, these will enable several shelves to be fixed later and I'm planning on using long lengths of local larch waney board that we used building the shed last year and some scaffolding boards.